What Is the Central Nervous System?<\/h1>\r\n<\/div>\r\nThe [pb_glossary id=\"5933\"]central nervous system[\/pb_glossary] (CNS) is the part of the nervous system that includes the [pb_glossary id=\"5915\"]brain[\/pb_glossary] and [pb_glossary id=\"3010\"]spinal cord[\/pb_glossary]. The drawing below (Figure 8.5.2) shows the central nervous system as one of two main divisions of the total nervous system. The other main division is the [pb_glossary id=\"3009\"]peripheral nervous system[\/pb_glossary] (PNS). The CNS and PNS work together to control virtually all body functions.\r\n\r\n[caption id=\"attachment_3013\" align=\"aligncenter\" width=\"712\"]![\"Central](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/Overview_of_Nervous_System-2.jpg\")
Figure 8.5.2 The two main divisions of the nervous system: the central nervous system (CNS) \u2014 which includes the brain and spinal cord \u2014 and the peripheral nervous system (PNS), which includes nerves and ganglia (singular, ganglion), which transmit information between the CNS to the rest of the body.<\/em>[\/caption]\r\n\r\nThe delicate nervous tissues of the central nervous system are protected by major physical and chemical barriers. Physically, the brain and spinal cord are surrounded by tough [pb_glossary id=\"2929\"]meninges[\/pb_glossary], a three-layer protective sheath that also contains cushioning [pb_glossary id=\"5939\"]cerebrospinal fluid[\/pb_glossary]. The\u00a0bones\u00a0of the skull and spinal vertebrae also contribute to physically protecting the brain and spinal cord. Chemically, the brain and spinal cord are isolated from the circulation\u00a0\u2014\u00a0and most toxins or pathogens in the\u00a0blood\u00a0\u2014\u00a0by the\u00a0[pb_glossary id=\"5909\"]blood-brain barrier[\/pb_glossary].<\/strong>\u00a0The blood-brain barrier is a highly selective membrane formed of endothelial\u00a0cells\u00a0that separates the circulating\u00a0blood\u00a0from extracellular fluid in the CNS. The barrier allows\u00a0water, certain gases, glucose, and some other molecules needed by the brain and spinal cord to cross from the blood into the CNS, while keeping out potentially harmful substances. These physical and chemical barriers make the CNS less susceptible to injury than the PNS. However, damage to the CNS is likely to have more serious consequences.\r\n\r\nThe Brain<\/h1>\r\n<\/div>\r\nThe\u00a0[pb_glossary id=\"5915\"]brain[\/pb_glossary]<\/strong> is the control center of not only the rest of the nervous system, but of the entire organism. The adult brain makes up only about 2% of the body\u2019s weight, but it uses about 20% of the body\u2019s total energy. The brain contains an estimated 100 billion neurons, and each [pb_glossary id=\"2984\"]neuron[\/pb_glossary] has thousands of synaptic connections to other neurons. The brain also has about the same number of [pb_glossary id=\"2985\"]neuroglia[\/pb_glossary] as neurons. No wonder the brain uses so much energy! In addition, the brain uses mostly [pb_glossary id=\"5451\"]glucose[\/pb_glossary] for energy. As a result, if the brain is deprived of glucose, it can lead to unconsciousness. The brain is able to store some glucose in the form of [pb_glossary id=\"327\"]glycogen[\/pb_glossary], but in much smaller amounts than are found in the liver and skeletal muscles.\r\n\r\nThe brain controls such mental processes as reasoning, imagination, memory, and language. It also interprets information from the senses and commands the body to respond appropriately. It controls basic physical processes (such as breathing and heartbeat), as well as voluntary activities (such as walking and writing). The brain has three major regions: the hindbrain, the midbrain and the forebrain. These parts are shown in Figure 8.5.3 and described below.\r\n\r\n[caption id=\"attachment_3072\" align=\"aligncenter\" width=\"630\"]![\"Diagram](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/Diagram_showing_the_brain_stem_which_includes_the_medulla_oblongata_the_pons_and_the_midbrain_2_CRUK_294.svg_-2.png\")
Figure 8.5.3 Diagram of the forebrain, midbrain and hindbrain. <\/em>[\/caption]\r\n\r\n\r\n\r\n \r\n\r\n<\/div>\r\nThe Hindbrain<\/h2>\r\n[caption id=\"attachment_3077\" align=\"alignright\" width=\"367\"]![\"Hindbrain\"](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/Brain_bulbar_region.svg_-2.png\")
Figure 8.5.4 The hindbrain consists of the cerebellum,<\/em> medulla oblongata, and the pons. It plays the extremely important role of connecting the brain to the rest of the body via the spinal cord.<\/em>[\/caption]\r\n\r\nThe\u00a0[pb_glossary id=\"3073\"]hindbrain[\/pb_glossary], <\/strong>which includes the [pb_glossary id=\"5935\"]cerebellum[\/pb_glossary], [pb_glossary id=\"3075\"]medulla oblongata[\/pb_glossary], and the [pb_glossary id=\"3076\"]pons[\/pb_glossary]. The hindbrain is the lowest part of the brain. It resembles a stalk and platform on which the cerebrum is perched. The components of the hindbrain connect the rest of the brain with the spinal cord and passes nerve impulses between the brain and spinal cord.\r\nCerebellum<\/h3>\r\nThe\u00a0[pb_glossary id=\"5935\"]cerebellum[\/pb_glossary]<\/strong> is located just below the cerebrum and at the back of the brain behind the brain stem. It coordinates your voluntary movements, balance, and posture.\u00a0 Information from your inner ear, joints and muscles, and eyes are all knitted together in the cerebellum so that you have awareness of where you are in 3-dimensional space.\u00a0 Patients who have suffered damage to their cerebellum may suffer from balance disorder. In addition the cerebellum plays a major role in motor learning (like how to ride a bike or how to do a backflip on a trampoline) through trial and error.\u00a0 While traditionally, the cerebellum was thought to only be involved in motor functions, we now know that it also plays an important role in memory and learning.\r\nMedulla Oblongata<\/h3>\r\nThe\u00a0[pb_glossary id=\"3075\"]medulla oblongata[\/pb_glossary]<\/strong> makes up part of the brainstem and sits in front of and just below the cerebellum, at the very top of the spinal cord.\u00a0 It is responsible for control of heart rate, respiration rate and blood pressure, as well as reflexes such as vomiting, coughing, sneezing and swallowing.\r\nPons<\/h3>\r\nThe\u00a0[pb_glossary id=\"3076\"]pons[\/pb_glossary]<\/strong> is located in front of the cerebellum and above the medulla oblongata.\u00a0 It has several functions, including receiving sensory information from the face, regulating rate and depth of breaths, as well as sleep cycles.\r\nMidbrain<\/h2>\r\n[caption id=\"attachment_3079\" align=\"alignleft\" width=\"317\"]![\"Midbrain\"](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/Midbrain-2.png\")
Figure 8.5.5 The brainstem includes the midbrain, the pons and the medulla oblongata.<\/em>[\/caption]\r\n\r\nThe midbrain is the topmost part of the brainstem and is the essential connection between and brain and spinal cord.\u00a0 The three main parts of the midbrain are the colliculi, the tegmentum, and the cerebral peduncles.\u00a0 These structures are all considered part of the brainstem, which consists of the medulla oblongata, the pons and the midbrain.\r\nReticular Activating System<\/h3>\r\nThe [pb_glossary id=\"3082\"]reticular activating system[\/pb_glossary] (RAS) is responsible for the sleep-wake cycle and wakefulness.\u00a0 It also regulates attention, ability to focus and arousal.\r\nForebrain<\/h2>\r\nThe forebrain is the anterior (forwardmost) part of the brain and includes the cerebrum, the thalamus and hypothalamus, hippocampus, amygdala, and limbic system.\u00a0 This portion of the brain is responsible for processing incoming sensory information, performing complex cognitive activities (speech, abstract thought, etc) and governing voluntary motor movements.\u00a0 \u00a0The forebrain also controls body temperature, reproductive functions, eating, sleeping and the display of emotions.\r\nCerebrum<\/h3>\r\nThe\u00a0[pb_glossary id=\"5941\"]cerebrum[\/pb_glossary]<\/strong>\u00a0is the largest part of the brain. It controls conscious, intellectual functions.\u00a0Among other things,\u00a0it controls reasoning, language, memory, sight, touch, and hearing. When you read a book, play a video game, or recognize a classmate, you are using your cerebrum.\r\nHemispheres and Lateralization of the Cerebrum<\/h4>\r\nThe cerebrum is divided from front to back into two halves called the left and right\u00a0[pb_glossary id=\"3083\"]hemispheres[\/pb_glossary].<\/strong>\u00a0The two hemispheres are connected by a thick bundle of axons, known as the [pb_glossary id=\"5955\"]corpus callosum[\/pb_glossary], which lies deep within the brain. The corpus callosum is the main avenue of\u00a0communication between the two hemispheres. It connects each point in the cerebrum to the mirror-image point in the opposite hemisphere.\r\n\r\nThe right and left hemispheres of the cerebrum are similar in shape, and most areas of cerebrum are found in both hemispheres. Some areas, however, show\u00a0[pb_glossary id=\"3085\"]lateralization[\/pb_glossary],<\/strong>\u00a0or a\u00a0concentration\u00a0in one hemisphere or the other.\u00a0In most people, for example, language functions are more concentrated in the left hemisphere, whereas abstract reasoning and visual-spatial abilities are more concentrated in the right hemisphere.\r\n\r\nFor reasons that are not yet clear, each hemisphere of the brain interacts primarily with the opposite side of the body. The left side of the brain receives messages from and sends commands to the right side of the body, and the right side of the brain\u00a0receives messages from and sends commands to the left side of the body. Sensory nerves from the spinal cord to the brain and motor nerves from the brain to the spinal cord both cross the midline of the body at the level of the brain stem.\r\nLobes of the Cerebrum<\/h4>\r\nEach [pb_glossary id=\"3083\"]hemisphere[\/pb_glossary] of the cerebrum is further divided into the four lobes shown in Figure 8.5.6 and described below.\r\n\r\n[caption id=\"attachment_3086\" align=\"aligncenter\" width=\"680\"]![\"\"](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/BrainLobes-2.png\")
Figure 8.5.6 The cerebrum is organized into four lobes: frontal, parietal, occipital, and temporal.<\/em>[\/caption]\r\n\r\n\r\n\r\nEach hemisphere of the cerebrum consists of four parts, called lobes. Each lobe is associated with particular brain functions. Just one function of each lobe is listed here.\r\n\r\n<\/div>\r\n\r\n \t- The\u00a0[pb_glossary id=\"6021\"]frontal lobes[\/pb_glossary]<\/strong>\u00a0are located at the front of the brain behind the forehead. The frontal lobes are associated with executive functions, such as attention, self-control, planning, problem solving, reasoning, abstract thought, language, and personality.<\/li>\r\n \t
- The\u00a0[pb_glossary id=\"3088\"]parietal lobes[\/pb_glossary]<\/strong>\u00a0are located behind the frontal lobes at the top of the head. The parietal lobes are involved in sensation \u2014 including\u00a0temperature, touch, and taste. Reading and arithmetic are also functions of the parietal lobes.<\/li>\r\n \t
- The\u00a0[pb_glossary id=\"3089\"]temporal lobes[\/pb_glossary]<\/strong>\u00a0are located at the sides of the head below the frontal and parietal lobes. The temporal lobes enable hearing, the formation and retrieval of memories, and the integration of memories and sensations.<\/li>\r\n \t
- The\u00a0[pb_glossary id=\"3090\"]occipital lobes[\/pb_glossary]<\/strong>\u00a0are located at the back of the head below the parietal lobes. The occipital lobes are the smallest of the four pairs of lobes. They are dedicated almost solely to\u00a0vision.<\/li>\r\n<\/ul>\r\n
Cerebral Cortex<\/h4>\r\nMost of the information processing in the brain actually takes place in the\u00a0[pb_glossary id=\"5937\"]cerebral cortex[\/pb_glossary]<\/strong>, a rind of gray matter and other tissues just a few millimetres thick that makes up the outer surface of the cerebrum in both hemispheres of the brain. The cerebral cortex has many folds in it, greatly increasing the amount of surface area of the brain that can fit within the skull. Because of all the folds in the human cerebral cortex, it has a surface area of about 2,500 cm2<\/sup>\u00a0(2.5 ft2<\/sup>). The size and importance of the cerebral cortex is far greater in the human brain than the brains of any other vertebrates, including nonhuman\u00a0primates.\r\nThe Limbic System<\/h3>\r\nThe limbic system consists of the hypothalamus, thalamus, the hippocampus and amygdala. The structures and interacting areas of the\u00a0[pb_glossary id=\"3098\"]limbic system[\/pb_glossary]<\/b>\u00a0are involved in motivation, emotion, learning, and memory.\r\nThalamus and Hypothalamus<\/h4>\r\nSeveral structures are located deep within the brain and are important for communication between the brain and spinal cord (or the rest of the body). These structures include the hypothalamus and thalamus. The diagram below (Figure 8.5.7) shows where these structures are located in the brain. Like the two halves of the cerebrum, the hypothalamus and thalamus exist in two halves, one in each hemisphere.\r\n\r\n[caption id=\"attachment_3092\" align=\"alignleft\" width=\"363\"]![\"Thalamus](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/Diencephalon-2.jpg\")
Figure 8.5.7 Structures deep within the brain include the hypothalamus and thalamus.<\/em>[\/caption]\r\n\r\nThe\u00a0[pb_glossary id=\"2937\"]hypothalamus[\/pb_glossary]<\/strong>\u00a0is located just above the brain stem, and is about the size of an almond. The hypothalamus is responsible for certain metabolic processes and other activities of the [pb_glossary id=\"5899\"]autonomic nervous system[\/pb_glossary], including body\u00a0temperature,\u00a0heart\u00a0rate, hunger, thirst, fatigue, sleep, wakefulness, and circadian (24-hour) rhythms. The hypothalamus is also an important emotional center of the brain. The hypothalamus can regulate so many body functions because it responds to many different internal and external signals, including messages from the brain, light, steroid hormones, stress, and invading pathogens, among others.\r\n\r\nOne way the hypothalamus influences body functions is by synthesizing hormones that directly influence body processes. It synthesizes the hormone [pb_glossary id=\"3093\"]oxytocin[\/pb_glossary], which stimulates uterine contractions during childbirth and the letdown of milk during lactation. It also synthesizes [pb_glossary id=\"5893\"]antidiuretic hormone[\/pb_glossary], which stimulates the kidneys to reabsorb more water and excrete more concentrated urine. These two hormones are sent from the hypothalamus via a stalk-like structure called the infundibulum (see Figure 8.5.7) directly to the posterior (back) portion of the pituitary gland, which secretes them into the blood.\r\n\r\nThe main way the hypothalamus influences body functions is by controlling the\u00a0[pb_glossary id=\"2938\"]pituitary gland[\/pb_glossary], known as the master gland of the\u00a0endocrine system. The hypothalamus synthesizes neurohormones called releasing factors that travel through the infundibulum directly to the anterior (front) part of the pituitary gland. The releasing factors generally either stimulate or inhibit the secretion of anterior pituitary hormones, most of which control other glands of the endocrine system.\r\n\r\nThe\u00a0[pb_glossary id=\"3095\"]thalamus[\/pb_glossary],<\/strong> which is located near the hypothalamus (see Figure 8.5.7), is a major hub for information traveling back and forth between the spinal cord and cerebrum. It relays sensory signals to the cerebral cortex and motor signals to the spinal cord. It is also involved in the regulation of consciousness, sleep, and alertness.\r\n\r\nHippocampus and Amygdala<\/h4>\r\nThe [pb_glossary id=\"3096\"]hippocampus[\/pb_glossary] is a complex structure embedded deep in the temporal lobe.\u00a0 It plays a major role in learning and memory and contributes to regulation of motivation and emotion. The amygdala is the part of the brain responsible for formation and storage of memories associated with emotional events.\r\n\r\nWatch \"The Limbic System\" by Soton Brain Hub to learn about the location and functions of the limbic system.\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=jcrWPo_s6EE\r\n
The Limbic System, Soton Brain Hub, 2016.<\/p>\r\n\r\n
Spinal Cord<\/h1>\r\n<\/div>\r\nThe\u00a0[pb_glossary id=\"3010\"]spinal cord[\/pb_glossary]<\/strong> is a long, thin, tubular bundle of nervous tissues that extends from the brain stem and continues down the center of the back to the pelvis. It is highlighted in yellow in Figure 8.5.8. The spinal cord is enclosed within, but is shorter than, the vertebral column.\r\n\r\n[caption id=\"attachment_3099\" align=\"alignnone\" width=\"482\"]![\"Spinal](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/SpinalCord-2.png\")
Figure 8.5.8 The spinal cord (yellow) runs from the bottom of the brain to the lower back.<\/em>[\/caption]\r\nStructure of the Spinal Cord<\/h2>\r\nThe center of the spinal cord consists of gray matter, which is made up mainly of cell bodies of neurons, including interneurons and motor neurons. The gray matter is surrounded by white matter that consists mainly of myelinated axons of motor and sensory neurons. Spinal nerves, which connect the spinal cord to the PNS, exit from the spinal cord between vertebrae (see Figure 8.5.9).\r\n\r\n \r\n\r\n\r\n[caption id=\"attachment_3100\" align=\"alignleft\" width=\"291\"]![\"Vertebrae\"](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/Spinal_readjustment_3-2.jpg\")
Figure 8.5.9 This model shows three vertebrae (white) with branching spinal nerves (yellow) emerging from the either side of the spinal cord between vertebrae.<\/em>[\/caption]\r\n\r\n<\/div>\r\nFunctions of the Spinal Cord<\/h2>\r\nThe spinal cord serves as an information superhighway. It passes messages from the body to the brain and from the brain to the body. Sensory (afferent) nerves carry\u00a0nerve impulses\u00a0to the brain from sensory receptor\u00a0cells\u00a0everywhere in and on the body. Motor (efferent) nerves carry nerve impulses away from the brain to glands, organs, or\u00a0muscles throughout the body.\r\n\r\nThe spinal cord also independently controls certain rapid responses called\u00a0reflexes<\/strong> without any input from the brain. You can see how this may happen in Figure 8.5.10. A sensory receptor responds to a sensation and sends a nerve impulse along a sensory nerve to the spinal cord. In the spinal cord, the message passes to an interneuron and from the interneuron to a motor nerve, which carries the impulse to a muscle. The muscle contracts in response. These neuron connections form a reflex arc, which requires no input from the brain. No doubt you have experienced such reflex actions yourself. For example, you may have reached out to touch a pot on the stove, not realizing that it was very hot. Virtually at the same moment that you feel the burning heat, you jerk your arm back and remove your hand from the pot.\r\n\r\n \r\n\r\n\r\n[caption id=\"attachment_3101\" align=\"alignnone\" width=\"1038\"]![\"Reflex](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/1507_Short_and_Long_Reflexes-2.jpg\")
Figure 8.5.10 This diagram shows what happens in a long reflex (top), in which sensory nerves carry the message all the way to the spinal cord; and in a short reflex (bottom), in which sensory nerves travel only to a ganglion outside the spinal cord. Note that interneurons are involved in reflexes, connecting sensory and motor neurons, but they are not actually shown in the diagram.<\/em>[\/caption]\r\n\r\n<\/div>\r\nInjuries to the Spinal Cord<\/h2>\r\nPhysical damage to the spinal cord may result in\u00a0[pb_glossary id=\"3102\"]paralysis[\/pb_glossary],<\/strong> which is loss of sensation and movement in part of the body. Paralysis generally affects all the areas of the body below the level of the injury, because nerve impulses are interrupted and can no longer travel back and forth between the brain and body beyond that point. If an injury to the spinal cord produces nothing more than swelling, the symptoms may be transient. However, if nerve fibres (axons) in the spinal cord are badly damaged, the loss of function may be permanent. Experimental studies have shown that spinal nerve fibres attempt to regrow, but tissue destruction usually produces scar tissue that cannot be penetrated by the regrowing nerves, as well other factors that inhibit nerve fibre regrowth in the central nervous system.\r\n\r\nFeature: My\u00a0Human Body<\/h1>\r\n<\/div>\r\nEach year, many millions of people have a stroke<\/a>, and stroke is the second leading cause of death in adults.\u00a0[pb_glossary id=\"3103\"]Stroke[\/pb_glossary],<\/strong>\u00a0also known as cerebrovascular accident, occurs when poor blood flow to the brain results in the death of brain cells. There are two main types of strokes:\r\n\r\n \t- Ischemic strokes occur due to lack of blood flow because of a blood clot in an artery going to the brain.<\/li>\r\n \t
- Hemorrhagic strokes occur due to bleeding from a broken blood vessel in the brain.<\/li>\r\n<\/ul>\r\nEither type of stroke may result in paralysis, loss of the ability to speak or comprehend speech, loss of bladder control, personality changes, and many other potential effects, depending on the part of the brain that is injured. The effects of a stroke may be mild and transient or more severe and permanent. A stroke may even be fatal. It generally depends on the type of stroke and how extensive it is.\r\n\r\nAre you at risk of a stroke? The main risk factor for stroke is age \u2014 about two-thirds of strokes occur in people over the age of 65. There is nothing you can do about your age, but most other stroke risk factors can be reduced with lifestyle changes or medications. The risk factors include high blood pressure, tobacco smoking, obesity, high blood cholesterol, diabetes mellitus, and atrial fibrillation.\r\n\r\nChances are good that you or someone you know is at risk of a stroke, so it is important to recognize a stroke if one occurs. A stroke is a medical emergency, and the more quickly treatment is given, the better the outcome is likely to be. In the case of ischemic strokes, the use of clot-busting drugs may prevent permanent brain damage if administered within three or four hours of the stroke. Remembering the signs of a stroke is easy. They are summed up by the acronym FAST.\r\n\r\n
\r\n8.5 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- The [pb_glossary id=\"5933\"]central nervous system[\/pb_glossary] is the part of the nervous system that includes the [pb_glossary id=\"5915\"]brain[\/pb_glossary] and [pb_glossary id=\"3010\"]spinal cord[\/pb_glossary]. It is physically protected by\u00a0bones, meninges, and [pb_glossary id=\"5939\"]cerebrospinal fluid[\/pb_glossary]. It is chemically protected by the blood-brain barrier.<\/li>\r\n \t
- The brain is the control center of the nervous system and of the entire organism. The brain uses a relatively large proportion of the body\u2019s\u00a0energy, primarily in the form of glucose.<\/li>\r\n \t
- The brain is divided into three major parts, each with different functions: the hindbrain, the midbrain and the forebrain.<\/li>\r\n \t
- Hindbrain consists of the medulla oblongata, the pons and the cerebellum, each of which perform specific functions.<\/li>\r\n \t
- The midbrain is primarily responsible for motor movement and in auditory and visual processing.<\/li>\r\n \t
- The forebrain contains many structures including:\r\n
\r\n \t- The cerebrum, which is further divided into left and right hemispheres. Each hemisphere has four lobes: frontal, parietal, temporal, and occipital. Each lobe is associated with specific senses or other functions.<\/li>\r\n \t
- The cerebrum\u00a0has a\u00a0thin outer layer called the cerebral cortex. Its many folds give it a large surface area. This is where most information processing takes place.<\/li>\r\n \t
- Inner structures of the brain include the hypothalamus \u2014 which controls the\u00a0endocrine system\u00a0via the\u00a0pituitary gland\u00a0\u2014 and the thalamus, which has several involuntary functions.<\/li>\r\n \t
- The hippocampus and amygdala, which are part of the limbic system and play important roles in memory, learning and emotions.<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t
- The spinal cord is a tubular bundle of nervous tissues that extends from the head down the middle of the back to the pelvis. It functions mainly to connect the brain with the\u00a0peripheral nervous system. It also controls certain rapid responses called reflexes without any input from the brain.<\/li>\r\n \t
- A spinal cord injury may lead to paralysis (loss of sensation and movement) of the body below the level of the injury, because nerve impulses can no longer travel up and down the spinal cord beyond that point.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n8.5 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- What is the central nervous system?<\/li>\r\n \t
- How is the central nervous system protected?<\/li>\r\n \t
- What is the overall function of the brain?<\/li>\r\n \t
- Identify the three main parts of the brain and one function of each part.<\/li>\r\n \t
- Describe the hemispheres of the brain.<\/li>\r\n \t
- Explain and give examples of lateralization of the brain.<\/li>\r\n \t
- Identify one function of each of the four lobes of the cerebrum.<\/li>\r\n \t
- [h5p id=\"562\"]<\/li>\r\n \t
- [h5p id=\"563\"]<\/li>\r\n \t
- Summarize the structure and function of the cerebral cortex. Explain how the hypothalamus controls the endocrine system.<\/li>\r\n \t
- Describe the spinal cord.<\/li>\r\n \t
- What is the main function of the spinal cord?<\/li>\r\n \t
- Explain how reflex actions occur.<\/li>\r\n \t
- Why do severe spinal cord injuries usually cause paralysis?<\/li>\r\n \t
- What do you think are some possible consequences of severe damage to the brain stem? How might this compare to the consequences of severe damage to the frontal lobe? Explain your answer.<\/li>\r\n \t
- Information travels very quickly in the nervous system, but generally, the longer the path between areas, the longer it takes. Based on this, explain why you think reflexes often occur at the spinal cord level, and do not require input from the brain.<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
\r\n8.5 Explore More<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=sewhbmh0ECg\r\nWhat if we could look inside human brains? - Moran Cerf, TED-Ed, 2013.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=ZMSbDwpIyF4\r\n
The left brain vs. right brain myth - Elizabeth Waters, TED-Ed, 2017.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?time_continue=1&v=aCv4K5aStdU&feature=emb_logo\r\n
Split-brain patient 'Joe' being tested with stimuli presented in different visual fields,\r\nmarkmcdermott, 2010.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n
Attributes<\/h2>\r\nFigure 8.5.1<\/strong>\r\n\r\nSensory_Homunculus-en.svg<\/a> by Popadius<\/a> on Wikimedia Commons is used under a CC BY 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0\/deed.en) license. (This is a derivative work from File:1421 Sensory Homunculus<\/a>.jpg by OpenStax College<\/a>)\r\n\r\nFigure 8.5.2<\/strong>\r\n\r\nOverview_of_Nervous_System<\/a>\u00a0by OpenStax<\/a> on Wikimedia Commons is used under a CC BY 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en) license.\r\n\r\nFigure 8.5.3<\/strong>\r\n\r\nDiagram_showing_the_brain_stem_which_includes_the_medulla_oblongata,_the_pons_and_the_midbrain_(2)_CRUK_294.svg<\/a> by Cancer Research UK<\/a> on Wikimedia Commons is used under a CC BY-SA 4.0 <\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\nFigure 8.5.4<\/strong>\r\n\r\nBrain_bulbar_region.svg<\/a> by Fvasconcellos<\/a> on Wikimedia Commons is used under a CC BY 2.5<\/a> license (derivative work from Brain human sagittal section.svg<\/a>\u00a0 by Patrick J. Lynch; Brain bulbar region.PNG<\/a> by DO11.10<\/a>).\r\n\r\nFigure 8.5.5<\/strong>\r\n\r\nMidbrain<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY 3.0 <\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0) license.\r\n\r\nFigure 8.5.6<\/strong>\r\n\r\nBrainLobes<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY 3.0 <\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0) license.\u00a0<\/span>\r\n\r\nFigure 8.5.7<\/strong>\r\n\r\nDiencephalon<\/a> by OpenStax<\/a> Wikimedia Commons is used under a CC BY 4.0 <\/a>(https:\/\/creativecommons.org\/licenses\/by\/4.0) license.\r\n\r\nFigure 8.5.8<\/strong>\r\n\r\nSpinalCord<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY 3.0 <\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0) license.\u00a0<\/span>\r\n\r\nFigure 8.5.9<\/strong>\r\n\r\nSpinal_readjustment_3<\/a> by Tomwsulcer<\/a> on\u00a0 Wikimedia Commons is used under a CC0 1.0<\/a> Universal Public Domain Dedication license (https:\/\/creativecommons.org\/publicdomain\/zero\/1.0\/deed.en).\r\n\r\nFigure 8.5.10<\/strong>\r\n\r\n1507_Short_and_Long_Reflexes<\/a> by OpenStax<\/a> on Wikimedia Commons is used under a CC BY 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en) license.\r\nReferences<\/h2>\r\n
Betts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2013, 28 May). Figure 14.23<\/span>\u00a0<\/span>The sensory homunculus <\/span>[digital image]. In Anatomy and Physiology<\/em> (Section 14.2). OpenStax. https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/14-2-central-processing\r\n<\/span><\/span><\/p>\r\nBetts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2013, 28 May). Figure 15.8 Short and long reflexes [digital image]. In Anatomy and Physiology<\/em> (Section 15.2). OpenStax. https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/15-2-autonomic-reflexes-and-homeostasis<\/p>\r\nBetts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2016, May 18). <\/span><\/span>Figure 12.2 Central and peripheral nervous system [digital image]. In Anatomy and Physiology<\/em> (Section 12.1). https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/12-1-basic-structure-and-function-of-the-nervous-system<\/span><\/span><\/p>\r\nBetts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2016, May 18). Figure 13.11 The diencephalon [digital image]. In Anatomy and Physiology<\/em> (Section 13.2). https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/13-2-the-central-nervous-system<\/p>\r\nBlausen.com staff. (2014). Medical gallery of Blausen Medical 2014. WikiJournal of Medicine,<\/em> 1<\/em> (2). DOI:10.15347\/wjm\/2014.010. ISSN 2002-4436<\/span><\/p>\r\nmarkmcdermott. (2010). Split-brain patient 'Joe' being tested with stimuli presented in different visual fields. YouTube. https:\/\/www.youtube.com\/user\/markmcdermott\/search?query=split<\/p>\r\n
Mayo Clinic Staff. (n.d.). Stroke [online article]. MayoClinic.org. https:\/\/www.mayoclinic.org\/diseases-conditions\/stroke\/symptoms-causes\/syc-20350113<\/p>\r\n
Soton Brain Hub. (2016, July 29). The limbic system. YouTube. https:\/\/www.youtube.com\/watch?v=jcrWPo_s6EE&feature=youtu.be<\/p>\r\n
TED-Ed. (2013, January 31). What if we could look inside human brains? - Moran Cerf. YouTube. https:\/\/www.youtube.com\/watch?v=sewhbmh0ECg&feature=youtu.be<\/p>\r\n
TED-Ed. (2017, July 24). The left brain vs. right brain myth - Elizabeth Waters. YouTube. https:\/\/www.youtube.com\/watch?v=ZMSbDwpIyF4&feature=youtu.be<\/p>\r\n ","rendered":"
<\/p>\n![\"Sensory](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2019\/06\/Sensory_Homunculus-en.svg_-2.png\")
Figure 8.5.1 This picture is called an <\/em>homunculus.\u00a0<\/em><\/figcaption><\/figure>\nHomunculus<\/h1>\n
The very odd-looking drawing in Figure 8.5.1 is called a homunculus. The beige mass represents a cross-sectional wedge of the human brain, and the drawing shows some areas of the brain associated with different parts of the body. As you can see, larger areas of the brain in this region are associated with the hands, face, and tongue, as compared to the areas associated with the legs and feet. Given the importance of speech, manual dexterity, and face-to-face social interactions in human beings, it is not surprising that relatively large areas of the brain are needed to control these body parts. The brain is the most complex organ in the human body and part of the central nervous system.<\/p>\n
\nWhat Is the Central Nervous System?<\/h1>\n<\/div>\n
The central nervous system<\/a> (CNS) is the part of the nervous system that includes the brain<\/a> and spinal cord<\/a>. The drawing below (Figure 8.5.2) shows the central nervous system as one of two main divisions of the total nervous system. The other main division is the peripheral nervous system<\/a> (PNS). The CNS and PNS work together to control virtually all body functions.<\/p>\nFigure 8.5.2 The two main divisions of the nervous system: the central nervous system (CNS) \u2014 which includes the brain and spinal cord \u2014 and the peripheral nervous system (PNS), which includes nerves and ganglia (singular, ganglion), which transmit information between the CNS to the rest of the body.<\/em><\/figcaption><\/figure>\nThe delicate nervous tissues of the central nervous system are protected by major physical and chemical barriers. Physically, the brain and spinal cord are surrounded by tough meninges<\/a>, a three-layer protective sheath that also contains cushioning cerebrospinal fluid<\/a>. The\u00a0bones\u00a0of the skull and spinal vertebrae also contribute to physically protecting the brain and spinal cord. Chemically, the brain and spinal cord are isolated from the circulation\u00a0\u2014\u00a0and most toxins or pathogens in the\u00a0blood\u00a0\u2014\u00a0by the\u00a0blood-brain barrier<\/a>.<\/strong>\u00a0The blood-brain barrier is a highly selective membrane formed of endothelial\u00a0cells\u00a0that separates the circulating\u00a0blood\u00a0from extracellular fluid in the CNS. The barrier allows\u00a0water, certain gases, glucose, and some other molecules needed by the brain and spinal cord to cross from the blood into the CNS, while keeping out potentially harmful substances. These physical and chemical barriers make the CNS less susceptible to injury than the PNS. However, damage to the CNS is likely to have more serious consequences.<\/p>\n\nThe Brain<\/h1>\n<\/div>\n
The\u00a0brain<\/a><\/strong> is the control center of not only the rest of the nervous system, but of the entire organism. The adult brain makes up only about 2% of the body\u2019s weight, but it uses about 20% of the body\u2019s total energy. The brain contains an estimated 100 billion neurons, and each neuron<\/a> has thousands of synaptic connections to other neurons. The brain also has about the same number of neuroglia<\/a> as neurons. No wonder the brain uses so much energy! In addition, the brain uses mostly glucose<\/a> for energy. As a result, if the brain is deprived of glucose, it can lead to unconsciousness. The brain is able to store some glucose in the form of glycogen, but in much smaller amounts than are found in the liver and skeletal muscles.<\/p>\nThe brain controls such mental processes as reasoning, imagination, memory, and language. It also interprets information from the senses and commands the body to respond appropriately. It controls basic physical processes (such as breathing and heartbeat), as well as voluntary activities (such as walking and writing). The brain has three major regions: the hindbrain, the midbrain and the forebrain. These parts are shown in Figure 8.5.3 and described below.<\/p>\nFigure 8.5.3 Diagram of the forebrain, midbrain and hindbrain. <\/em><\/figcaption><\/figure>\n\n <\/p>\n<\/div>\n
The Hindbrain<\/h2>\nFigure 8.5.4 The hindbrain consists of the cerebellum,<\/em> medulla oblongata, and the pons. It plays the extremely important role of connecting the brain to the rest of the body via the spinal cord.<\/em><\/figcaption><\/figure>\nThe\u00a0hindbrain<\/a>, <\/strong>which includes the cerebellum<\/a>, medulla oblongata<\/a>, and the pons<\/a>. The hindbrain is the lowest part of the brain. It resembles a stalk and platform on which the cerebrum is perched. The components of the hindbrain connect the rest of the brain with the spinal cord and passes nerve impulses between the brain and spinal cord.<\/p>\nCerebellum<\/h3>\n
The\u00a0cerebellum<\/a><\/strong> is located just below the cerebrum and at the back of the brain behind the brain stem. It coordinates your voluntary movements, balance, and posture.\u00a0 Information from your inner ear, joints and muscles, and eyes are all knitted together in the cerebellum so that you have awareness of where you are in 3-dimensional space.\u00a0 Patients who have suffered damage to their cerebellum may suffer from balance disorder. In addition the cerebellum plays a major role in motor learning (like how to ride a bike or how to do a backflip on a trampoline) through trial and error.\u00a0 While traditionally, the cerebellum was thought to only be involved in motor functions, we now know that it also plays an important role in memory and learning.<\/p>\nMedulla Oblongata<\/h3>\n
The\u00a0medulla oblongata<\/a><\/strong> makes up part of the brainstem and sits in front of and just below the cerebellum, at the very top of the spinal cord.\u00a0 It is responsible for control of heart rate, respiration rate and blood pressure, as well as reflexes such as vomiting, coughing, sneezing and swallowing.<\/p>\nPons<\/h3>\n
The\u00a0pons<\/a><\/strong> is located in front of the cerebellum and above the medulla oblongata.\u00a0 It has several functions, including receiving sensory information from the face, regulating rate and depth of breaths, as well as sleep cycles.<\/p>\nMidbrain<\/h2>\nFigure 8.5.5 The brainstem includes the midbrain, the pons and the medulla oblongata.<\/em><\/figcaption><\/figure>\nThe midbrain is the topmost part of the brainstem and is the essential connection between and brain and spinal cord.\u00a0 The three main parts of the midbrain are the colliculi, the tegmentum, and the cerebral peduncles.\u00a0 These structures are all considered part of the brainstem, which consists of the medulla oblongata, the pons and the midbrain.<\/p>\n
Reticular Activating System<\/h3>\n
The reticular activating system<\/a> (RAS) is responsible for the sleep-wake cycle and wakefulness.\u00a0 It also regulates attention, ability to focus and arousal.<\/p>\nForebrain<\/h2>\n
The forebrain is the anterior (forwardmost) part of the brain and includes the cerebrum, the thalamus and hypothalamus, hippocampus, amygdala, and limbic system.\u00a0 This portion of the brain is responsible for processing incoming sensory information, performing complex cognitive activities (speech, abstract thought, etc) and governing voluntary motor movements.\u00a0 \u00a0The forebrain also controls body temperature, reproductive functions, eating, sleeping and the display of emotions.<\/p>\n
Cerebrum<\/h3>\n
The\u00a0cerebrum<\/a><\/strong>\u00a0is the largest part of the brain. It controls conscious, intellectual functions.\u00a0Among other things,\u00a0it controls reasoning, language, memory, sight, touch, and hearing. When you read a book, play a video game, or recognize a classmate, you are using your cerebrum.<\/p>\nHemispheres and Lateralization of the Cerebrum<\/h4>\n
The cerebrum is divided from front to back into two halves called the left and right\u00a0hemispheres<\/a>.<\/strong>\u00a0The two hemispheres are connected by a thick bundle of axons, known as the corpus callosum<\/a>, which lies deep within the brain. The corpus callosum is the main avenue of\u00a0communication between the two hemispheres. It connects each point in the cerebrum to the mirror-image point in the opposite hemisphere.<\/p>\nThe right and left hemispheres of the cerebrum are similar in shape, and most areas of cerebrum are found in both hemispheres. Some areas, however, show\u00a0lateralization<\/a>,<\/strong>\u00a0or a\u00a0concentration\u00a0in one hemisphere or the other.\u00a0In most people, for example, language functions are more concentrated in the left hemisphere, whereas abstract reasoning and visual-spatial abilities are more concentrated in the right hemisphere.<\/p>\nFor reasons that are not yet clear, each hemisphere of the brain interacts primarily with the opposite side of the body. The left side of the brain receives messages from and sends commands to the right side of the body, and the right side of the brain\u00a0receives messages from and sends commands to the left side of the body. Sensory nerves from the spinal cord to the brain and motor nerves from the brain to the spinal cord both cross the midline of the body at the level of the brain stem.<\/p>\n
Lobes of the Cerebrum<\/h4>\n
Each hemisphere<\/a> of the cerebrum is further divided into the four lobes shown in Figure 8.5.6 and described below.<\/p>\nFigure 8.5.6 The cerebrum is organized into four lobes: frontal, parietal, occipital, and temporal.<\/em><\/figcaption><\/figure>\n\nEach hemisphere of the cerebrum consists of four parts, called lobes. Each lobe is associated with particular brain functions. Just one function of each lobe is listed here.<\/p>\n<\/div>\n
\n- The\u00a0frontal lobes<\/a><\/strong>\u00a0are located at the front of the brain behind the forehead. The frontal lobes are associated with executive functions, such as attention, self-control, planning, problem solving, reasoning, abstract thought, language, and personality.<\/li>\n
- The\u00a0parietal lobes<\/a><\/strong>\u00a0are located behind the frontal lobes at the top of the head. The parietal lobes are involved in sensation \u2014 including\u00a0temperature, touch, and taste. Reading and arithmetic are also functions of the parietal lobes.<\/li>\n
- The\u00a0temporal lobes<\/a><\/strong>\u00a0are located at the sides of the head below the frontal and parietal lobes. The temporal lobes enable hearing, the formation and retrieval of memories, and the integration of memories and sensations.<\/li>\n
- The\u00a0occipital lobes<\/a><\/strong>\u00a0are located at the back of the head below the parietal lobes. The occipital lobes are the smallest of the four pairs of lobes. They are dedicated almost solely to\u00a0vision.<\/li>\n<\/ul>\n
Cerebral Cortex<\/h4>\n
Most of the information processing in the brain actually takes place in the\u00a0cerebral cortex<\/a><\/strong>, a rind of gray matter and other tissues just a few millimetres thick that makes up the outer surface of the cerebrum in both hemispheres of the brain. The cerebral cortex has many folds in it, greatly increasing the amount of surface area of the brain that can fit within the skull. Because of all the folds in the human cerebral cortex, it has a surface area of about 2,500 cm2<\/sup>\u00a0(2.5 ft2<\/sup>). The size and importance of the cerebral cortex is far greater in the human brain than the brains of any other vertebrates, including nonhuman\u00a0primates.<\/p>\nThe Limbic System<\/h3>\n
The limbic system consists of the hypothalamus, thalamus, the hippocampus and amygdala. The structures and interacting areas of the\u00a0limbic system<\/a><\/b>\u00a0are involved in motivation, emotion, learning, and memory.<\/p>\nThalamus and Hypothalamus<\/h4>\n
Several structures are located deep within the brain and are important for communication between the brain and spinal cord (or the rest of the body). These structures include the hypothalamus and thalamus. The diagram below (Figure 8.5.7) shows where these structures are located in the brain. Like the two halves of the cerebrum, the hypothalamus and thalamus exist in two halves, one in each hemisphere.<\/p>\nFigure 8.5.7 Structures deep within the brain include the hypothalamus and thalamus.<\/em><\/figcaption><\/figure>\nThe\u00a0hypothalamus<\/a><\/strong>\u00a0is located just above the brain stem, and is about the size of an almond. The hypothalamus is responsible for certain metabolic processes and other activities of the autonomic nervous system<\/a>, including body\u00a0temperature,\u00a0heart\u00a0rate, hunger, thirst, fatigue, sleep, wakefulness, and circadian (24-hour) rhythms. The hypothalamus is also an important emotional center of the brain. The hypothalamus can regulate so many body functions because it responds to many different internal and external signals, including messages from the brain, light, steroid hormones, stress, and invading pathogens, among others.<\/p>\nOne way the hypothalamus influences body functions is by synthesizing hormones that directly influence body processes. It synthesizes the hormone oxytocin<\/a>, which stimulates uterine contractions during childbirth and the letdown of milk during lactation. It also synthesizes antidiuretic hormone<\/a>, which stimulates the kidneys to reabsorb more water and excrete more concentrated urine. These two hormones are sent from the hypothalamus via a stalk-like structure called the infundibulum (see Figure 8.5.7) directly to the posterior (back) portion of the pituitary gland, which secretes them into the blood.<\/p>\nThe main way the hypothalamus influences body functions is by controlling the\u00a0pituitary gland<\/a>, known as the master gland of the\u00a0endocrine system. The hypothalamus synthesizes neurohormones called releasing factors that travel through the infundibulum directly to the anterior (front) part of the pituitary gland. The releasing factors generally either stimulate or inhibit the secretion of anterior pituitary hormones, most of which control other glands of the endocrine system.<\/p>\n
The Brain<\/h1>\r\n<\/div>\r\nThe\u00a0[pb_glossary id=\"5915\"]brain[\/pb_glossary]<\/strong> is the control center of not only the rest of the nervous system, but of the entire organism. The adult brain makes up only about 2% of the body\u2019s weight, but it uses about 20% of the body\u2019s total energy. The brain contains an estimated 100 billion neurons, and each [pb_glossary id=\"2984\"]neuron[\/pb_glossary] has thousands of synaptic connections to other neurons. The brain also has about the same number of [pb_glossary id=\"2985\"]neuroglia[\/pb_glossary] as neurons. No wonder the brain uses so much energy! In addition, the brain uses mostly [pb_glossary id=\"5451\"]glucose[\/pb_glossary] for energy. As a result, if the brain is deprived of glucose, it can lead to unconsciousness. The brain is able to store some glucose in the form of [pb_glossary id=\"327\"]glycogen[\/pb_glossary], but in much smaller amounts than are found in the liver and skeletal muscles.\r\n\r\nThe brain controls such mental processes as reasoning, imagination, memory, and language. It also interprets information from the senses and commands the body to respond appropriately. It controls basic physical processes (such as breathing and heartbeat), as well as voluntary activities (such as walking and writing). The brain has three major regions: the hindbrain, the midbrain and the forebrain. These parts are shown in Figure 8.5.3 and described below.\r\n\r\n[caption id=\"attachment_3072\" align=\"aligncenter\" width=\"630\"] Figure 8.5.3 Diagram of the forebrain, midbrain and hindbrain. <\/em>[\/caption]\r\n\r\n\r\n\r\n \r\n\r\n<\/div>\r\nThe Hindbrain<\/h2>\r\n[caption id=\"attachment_3077\" align=\"alignright\" width=\"367\"] Figure 8.5.4 The hindbrain consists of the cerebellum,<\/em> medulla oblongata, and the pons. It plays the extremely important role of connecting the brain to the rest of the body via the spinal cord.<\/em>[\/caption]\r\n\r\nThe\u00a0[pb_glossary id=\"3073\"]hindbrain[\/pb_glossary], <\/strong>which includes the [pb_glossary id=\"5935\"]cerebellum[\/pb_glossary], [pb_glossary id=\"3075\"]medulla oblongata[\/pb_glossary], and the [pb_glossary id=\"3076\"]pons[\/pb_glossary]. The hindbrain is the lowest part of the brain. It resembles a stalk and platform on which the cerebrum is perched. The components of the hindbrain connect the rest of the brain with the spinal cord and passes nerve impulses between the brain and spinal cord.\r\nCerebellum<\/h3>\r\nThe\u00a0[pb_glossary id=\"5935\"]cerebellum[\/pb_glossary]<\/strong> is located just below the cerebrum and at the back of the brain behind the brain stem. It coordinates your voluntary movements, balance, and posture.\u00a0 Information from your inner ear, joints and muscles, and eyes are all knitted together in the cerebellum so that you have awareness of where you are in 3-dimensional space.\u00a0 Patients who have suffered damage to their cerebellum may suffer from balance disorder. In addition the cerebellum plays a major role in motor learning (like how to ride a bike or how to do a backflip on a trampoline) through trial and error.\u00a0 While traditionally, the cerebellum was thought to only be involved in motor functions, we now know that it also plays an important role in memory and learning.\r\nMedulla Oblongata<\/h3>\r\nThe\u00a0[pb_glossary id=\"3075\"]medulla oblongata[\/pb_glossary]<\/strong> makes up part of the brainstem and sits in front of and just below the cerebellum, at the very top of the spinal cord.\u00a0 It is responsible for control of heart rate, respiration rate and blood pressure, as well as reflexes such as vomiting, coughing, sneezing and swallowing.\r\nPons<\/h3>\r\nThe\u00a0[pb_glossary id=\"3076\"]pons[\/pb_glossary]<\/strong> is located in front of the cerebellum and above the medulla oblongata.\u00a0 It has several functions, including receiving sensory information from the face, regulating rate and depth of breaths, as well as sleep cycles.\r\nMidbrain<\/h2>\r\n[caption id=\"attachment_3079\" align=\"alignleft\" width=\"317\"] Figure 8.5.5 The brainstem includes the midbrain, the pons and the medulla oblongata.<\/em>[\/caption]\r\n\r\nThe midbrain is the topmost part of the brainstem and is the essential connection between and brain and spinal cord.\u00a0 The three main parts of the midbrain are the colliculi, the tegmentum, and the cerebral peduncles.\u00a0 These structures are all considered part of the brainstem, which consists of the medulla oblongata, the pons and the midbrain.\r\nReticular Activating System<\/h3>\r\nThe [pb_glossary id=\"3082\"]reticular activating system[\/pb_glossary] (RAS) is responsible for the sleep-wake cycle and wakefulness.\u00a0 It also regulates attention, ability to focus and arousal.\r\nForebrain<\/h2>\r\nThe forebrain is the anterior (forwardmost) part of the brain and includes the cerebrum, the thalamus and hypothalamus, hippocampus, amygdala, and limbic system.\u00a0 This portion of the brain is responsible for processing incoming sensory information, performing complex cognitive activities (speech, abstract thought, etc) and governing voluntary motor movements.\u00a0 \u00a0The forebrain also controls body temperature, reproductive functions, eating, sleeping and the display of emotions.\r\nCerebrum<\/h3>\r\nThe\u00a0[pb_glossary id=\"5941\"]cerebrum[\/pb_glossary]<\/strong>\u00a0is the largest part of the brain. It controls conscious, intellectual functions.\u00a0Among other things,\u00a0it controls reasoning, language, memory, sight, touch, and hearing. When you read a book, play a video game, or recognize a classmate, you are using your cerebrum.\r\nHemispheres and Lateralization of the Cerebrum<\/h4>\r\nThe cerebrum is divided from front to back into two halves called the left and right\u00a0[pb_glossary id=\"3083\"]hemispheres[\/pb_glossary].<\/strong>\u00a0The two hemispheres are connected by a thick bundle of axons, known as the [pb_glossary id=\"5955\"]corpus callosum[\/pb_glossary], which lies deep within the brain. The corpus callosum is the main avenue of\u00a0communication between the two hemispheres. It connects each point in the cerebrum to the mirror-image point in the opposite hemisphere.\r\n\r\nThe right and left hemispheres of the cerebrum are similar in shape, and most areas of cerebrum are found in both hemispheres. Some areas, however, show\u00a0[pb_glossary id=\"3085\"]lateralization[\/pb_glossary],<\/strong>\u00a0or a\u00a0concentration\u00a0in one hemisphere or the other.\u00a0In most people, for example, language functions are more concentrated in the left hemisphere, whereas abstract reasoning and visual-spatial abilities are more concentrated in the right hemisphere.\r\n\r\nFor reasons that are not yet clear, each hemisphere of the brain interacts primarily with the opposite side of the body. The left side of the brain receives messages from and sends commands to the right side of the body, and the right side of the brain\u00a0receives messages from and sends commands to the left side of the body. Sensory nerves from the spinal cord to the brain and motor nerves from the brain to the spinal cord both cross the midline of the body at the level of the brain stem.\r\nLobes of the Cerebrum<\/h4>\r\nEach [pb_glossary id=\"3083\"]hemisphere[\/pb_glossary] of the cerebrum is further divided into the four lobes shown in Figure 8.5.6 and described below.\r\n\r\n[caption id=\"attachment_3086\" align=\"aligncenter\" width=\"680\"] Figure 8.5.6 The cerebrum is organized into four lobes: frontal, parietal, occipital, and temporal.<\/em>[\/caption]\r\n\r\n\r\n\r\nEach hemisphere of the cerebrum consists of four parts, called lobes. Each lobe is associated with particular brain functions. Just one function of each lobe is listed here.\r\n\r\n<\/div>\r\n\r\n \t- The\u00a0[pb_glossary id=\"6021\"]frontal lobes[\/pb_glossary]<\/strong>\u00a0are located at the front of the brain behind the forehead. The frontal lobes are associated with executive functions, such as attention, self-control, planning, problem solving, reasoning, abstract thought, language, and personality.<\/li>\r\n \t
- The\u00a0[pb_glossary id=\"3088\"]parietal lobes[\/pb_glossary]<\/strong>\u00a0are located behind the frontal lobes at the top of the head. The parietal lobes are involved in sensation \u2014 including\u00a0temperature, touch, and taste. Reading and arithmetic are also functions of the parietal lobes.<\/li>\r\n \t
- The\u00a0[pb_glossary id=\"3089\"]temporal lobes[\/pb_glossary]<\/strong>\u00a0are located at the sides of the head below the frontal and parietal lobes. The temporal lobes enable hearing, the formation and retrieval of memories, and the integration of memories and sensations.<\/li>\r\n \t
- The\u00a0[pb_glossary id=\"3090\"]occipital lobes[\/pb_glossary]<\/strong>\u00a0are located at the back of the head below the parietal lobes. The occipital lobes are the smallest of the four pairs of lobes. They are dedicated almost solely to\u00a0vision.<\/li>\r\n<\/ul>\r\n
Cerebral Cortex<\/h4>\r\nMost of the information processing in the brain actually takes place in the\u00a0[pb_glossary id=\"5937\"]cerebral cortex[\/pb_glossary]<\/strong>, a rind of gray matter and other tissues just a few millimetres thick that makes up the outer surface of the cerebrum in both hemispheres of the brain. The cerebral cortex has many folds in it, greatly increasing the amount of surface area of the brain that can fit within the skull. Because of all the folds in the human cerebral cortex, it has a surface area of about 2,500 cm2<\/sup>\u00a0(2.5 ft2<\/sup>). The size and importance of the cerebral cortex is far greater in the human brain than the brains of any other vertebrates, including nonhuman\u00a0primates.\r\nThe Limbic System<\/h3>\r\nThe limbic system consists of the hypothalamus, thalamus, the hippocampus and amygdala. The structures and interacting areas of the\u00a0[pb_glossary id=\"3098\"]limbic system[\/pb_glossary]<\/b>\u00a0are involved in motivation, emotion, learning, and memory.\r\nThalamus and Hypothalamus<\/h4>\r\nSeveral structures are located deep within the brain and are important for communication between the brain and spinal cord (or the rest of the body). These structures include the hypothalamus and thalamus. The diagram below (Figure 8.5.7) shows where these structures are located in the brain. Like the two halves of the cerebrum, the hypothalamus and thalamus exist in two halves, one in each hemisphere.\r\n\r\n[caption id=\"attachment_3092\" align=\"alignleft\" width=\"363\"] Figure 8.5.7 Structures deep within the brain include the hypothalamus and thalamus.<\/em>[\/caption]\r\n\r\nThe\u00a0[pb_glossary id=\"2937\"]hypothalamus[\/pb_glossary]<\/strong>\u00a0is located just above the brain stem, and is about the size of an almond. The hypothalamus is responsible for certain metabolic processes and other activities of the [pb_glossary id=\"5899\"]autonomic nervous system[\/pb_glossary], including body\u00a0temperature,\u00a0heart\u00a0rate, hunger, thirst, fatigue, sleep, wakefulness, and circadian (24-hour) rhythms. The hypothalamus is also an important emotional center of the brain. The hypothalamus can regulate so many body functions because it responds to many different internal and external signals, including messages from the brain, light, steroid hormones, stress, and invading pathogens, among others.\r\n\r\nOne way the hypothalamus influences body functions is by synthesizing hormones that directly influence body processes. It synthesizes the hormone [pb_glossary id=\"3093\"]oxytocin[\/pb_glossary], which stimulates uterine contractions during childbirth and the letdown of milk during lactation. It also synthesizes [pb_glossary id=\"5893\"]antidiuretic hormone[\/pb_glossary], which stimulates the kidneys to reabsorb more water and excrete more concentrated urine. These two hormones are sent from the hypothalamus via a stalk-like structure called the infundibulum (see Figure 8.5.7) directly to the posterior (back) portion of the pituitary gland, which secretes them into the blood.\r\n\r\nThe main way the hypothalamus influences body functions is by controlling the\u00a0[pb_glossary id=\"2938\"]pituitary gland[\/pb_glossary], known as the master gland of the\u00a0endocrine system. The hypothalamus synthesizes neurohormones called releasing factors that travel through the infundibulum directly to the anterior (front) part of the pituitary gland. The releasing factors generally either stimulate or inhibit the secretion of anterior pituitary hormones, most of which control other glands of the endocrine system.\r\n\r\nThe\u00a0[pb_glossary id=\"3095\"]thalamus[\/pb_glossary],<\/strong> which is located near the hypothalamus (see Figure 8.5.7), is a major hub for information traveling back and forth between the spinal cord and cerebrum. It relays sensory signals to the cerebral cortex and motor signals to the spinal cord. It is also involved in the regulation of consciousness, sleep, and alertness.\r\n\r\nHippocampus and Amygdala<\/h4>\r\nThe [pb_glossary id=\"3096\"]hippocampus[\/pb_glossary] is a complex structure embedded deep in the temporal lobe.\u00a0 It plays a major role in learning and memory and contributes to regulation of motivation and emotion. The amygdala is the part of the brain responsible for formation and storage of memories associated with emotional events.\r\n\r\nWatch \"The Limbic System\" by Soton Brain Hub to learn about the location and functions of the limbic system.\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=jcrWPo_s6EE\r\n
The Limbic System, Soton Brain Hub, 2016.<\/p>\r\n\r\n
Spinal Cord<\/h1>\r\n<\/div>\r\nThe\u00a0[pb_glossary id=\"3010\"]spinal cord[\/pb_glossary]<\/strong> is a long, thin, tubular bundle of nervous tissues that extends from the brain stem and continues down the center of the back to the pelvis. It is highlighted in yellow in Figure 8.5.8. The spinal cord is enclosed within, but is shorter than, the vertebral column.\r\n\r\n[caption id=\"attachment_3099\" align=\"alignnone\" width=\"482\"] Figure 8.5.8 The spinal cord (yellow) runs from the bottom of the brain to the lower back.<\/em>[\/caption]\r\nStructure of the Spinal Cord<\/h2>\r\nThe center of the spinal cord consists of gray matter, which is made up mainly of cell bodies of neurons, including interneurons and motor neurons. The gray matter is surrounded by white matter that consists mainly of myelinated axons of motor and sensory neurons. Spinal nerves, which connect the spinal cord to the PNS, exit from the spinal cord between vertebrae (see Figure 8.5.9).\r\n\r\n \r\n\r\n\r\n[caption id=\"attachment_3100\" align=\"alignleft\" width=\"291\"] Figure 8.5.9 This model shows three vertebrae (white) with branching spinal nerves (yellow) emerging from the either side of the spinal cord between vertebrae.<\/em>[\/caption]\r\n\r\n<\/div>\r\nFunctions of the Spinal Cord<\/h2>\r\nThe spinal cord serves as an information superhighway. It passes messages from the body to the brain and from the brain to the body. Sensory (afferent) nerves carry\u00a0nerve impulses\u00a0to the brain from sensory receptor\u00a0cells\u00a0everywhere in and on the body. Motor (efferent) nerves carry nerve impulses away from the brain to glands, organs, or\u00a0muscles throughout the body.\r\n\r\nThe spinal cord also independently controls certain rapid responses called\u00a0reflexes<\/strong> without any input from the brain. You can see how this may happen in Figure 8.5.10. A sensory receptor responds to a sensation and sends a nerve impulse along a sensory nerve to the spinal cord. In the spinal cord, the message passes to an interneuron and from the interneuron to a motor nerve, which carries the impulse to a muscle. The muscle contracts in response. These neuron connections form a reflex arc, which requires no input from the brain. No doubt you have experienced such reflex actions yourself. For example, you may have reached out to touch a pot on the stove, not realizing that it was very hot. Virtually at the same moment that you feel the burning heat, you jerk your arm back and remove your hand from the pot.\r\n\r\n \r\n\r\n\r\n[caption id=\"attachment_3101\" align=\"alignnone\" width=\"1038\"] Figure 8.5.10 This diagram shows what happens in a long reflex (top), in which sensory nerves carry the message all the way to the spinal cord; and in a short reflex (bottom), in which sensory nerves travel only to a ganglion outside the spinal cord. Note that interneurons are involved in reflexes, connecting sensory and motor neurons, but they are not actually shown in the diagram.<\/em>[\/caption]\r\n\r\n<\/div>\r\nInjuries to the Spinal Cord<\/h2>\r\nPhysical damage to the spinal cord may result in\u00a0[pb_glossary id=\"3102\"]paralysis[\/pb_glossary],<\/strong> which is loss of sensation and movement in part of the body. Paralysis generally affects all the areas of the body below the level of the injury, because nerve impulses are interrupted and can no longer travel back and forth between the brain and body beyond that point. If an injury to the spinal cord produces nothing more than swelling, the symptoms may be transient. However, if nerve fibres (axons) in the spinal cord are badly damaged, the loss of function may be permanent. Experimental studies have shown that spinal nerve fibres attempt to regrow, but tissue destruction usually produces scar tissue that cannot be penetrated by the regrowing nerves, as well other factors that inhibit nerve fibre regrowth in the central nervous system.\r\n\r\nFeature: My\u00a0Human Body<\/h1>\r\n<\/div>\r\nEach year, many millions of people have a stroke<\/a>, and stroke is the second leading cause of death in adults.\u00a0[pb_glossary id=\"3103\"]Stroke[\/pb_glossary],<\/strong>\u00a0also known as cerebrovascular accident, occurs when poor blood flow to the brain results in the death of brain cells. There are two main types of strokes:\r\n\r\n \t- Ischemic strokes occur due to lack of blood flow because of a blood clot in an artery going to the brain.<\/li>\r\n \t
- Hemorrhagic strokes occur due to bleeding from a broken blood vessel in the brain.<\/li>\r\n<\/ul>\r\nEither type of stroke may result in paralysis, loss of the ability to speak or comprehend speech, loss of bladder control, personality changes, and many other potential effects, depending on the part of the brain that is injured. The effects of a stroke may be mild and transient or more severe and permanent. A stroke may even be fatal. It generally depends on the type of stroke and how extensive it is.\r\n\r\nAre you at risk of a stroke? The main risk factor for stroke is age \u2014 about two-thirds of strokes occur in people over the age of 65. There is nothing you can do about your age, but most other stroke risk factors can be reduced with lifestyle changes or medications. The risk factors include high blood pressure, tobacco smoking, obesity, high blood cholesterol, diabetes mellitus, and atrial fibrillation.\r\n\r\nChances are good that you or someone you know is at risk of a stroke, so it is important to recognize a stroke if one occurs. A stroke is a medical emergency, and the more quickly treatment is given, the better the outcome is likely to be. In the case of ischemic strokes, the use of clot-busting drugs may prevent permanent brain damage if administered within three or four hours of the stroke. Remembering the signs of a stroke is easy. They are summed up by the acronym FAST.\r\n\r\n
\r\n8.5 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- The [pb_glossary id=\"5933\"]central nervous system[\/pb_glossary] is the part of the nervous system that includes the [pb_glossary id=\"5915\"]brain[\/pb_glossary] and [pb_glossary id=\"3010\"]spinal cord[\/pb_glossary]. It is physically protected by\u00a0bones, meninges, and [pb_glossary id=\"5939\"]cerebrospinal fluid[\/pb_glossary]. It is chemically protected by the blood-brain barrier.<\/li>\r\n \t
- The brain is the control center of the nervous system and of the entire organism. The brain uses a relatively large proportion of the body\u2019s\u00a0energy, primarily in the form of glucose.<\/li>\r\n \t
- The brain is divided into three major parts, each with different functions: the hindbrain, the midbrain and the forebrain.<\/li>\r\n \t
- Hindbrain consists of the medulla oblongata, the pons and the cerebellum, each of which perform specific functions.<\/li>\r\n \t
- The midbrain is primarily responsible for motor movement and in auditory and visual processing.<\/li>\r\n \t
- The forebrain contains many structures including:\r\n
\r\n \t- The cerebrum, which is further divided into left and right hemispheres. Each hemisphere has four lobes: frontal, parietal, temporal, and occipital. Each lobe is associated with specific senses or other functions.<\/li>\r\n \t
- The cerebrum\u00a0has a\u00a0thin outer layer called the cerebral cortex. Its many folds give it a large surface area. This is where most information processing takes place.<\/li>\r\n \t
- Inner structures of the brain include the hypothalamus \u2014 which controls the\u00a0endocrine system\u00a0via the\u00a0pituitary gland\u00a0\u2014 and the thalamus, which has several involuntary functions.<\/li>\r\n \t
- The hippocampus and amygdala, which are part of the limbic system and play important roles in memory, learning and emotions.<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t
- The spinal cord is a tubular bundle of nervous tissues that extends from the head down the middle of the back to the pelvis. It functions mainly to connect the brain with the\u00a0peripheral nervous system. It also controls certain rapid responses called reflexes without any input from the brain.<\/li>\r\n \t
- A spinal cord injury may lead to paralysis (loss of sensation and movement) of the body below the level of the injury, because nerve impulses can no longer travel up and down the spinal cord beyond that point.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n8.5 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- What is the central nervous system?<\/li>\r\n \t
- How is the central nervous system protected?<\/li>\r\n \t
- What is the overall function of the brain?<\/li>\r\n \t
- Identify the three main parts of the brain and one function of each part.<\/li>\r\n \t
- Describe the hemispheres of the brain.<\/li>\r\n \t
- Explain and give examples of lateralization of the brain.<\/li>\r\n \t
- Identify one function of each of the four lobes of the cerebrum.<\/li>\r\n \t
- [h5p id=\"562\"]<\/li>\r\n \t
- [h5p id=\"563\"]<\/li>\r\n \t
- Summarize the structure and function of the cerebral cortex. Explain how the hypothalamus controls the endocrine system.<\/li>\r\n \t
- Describe the spinal cord.<\/li>\r\n \t
- What is the main function of the spinal cord?<\/li>\r\n \t
- Explain how reflex actions occur.<\/li>\r\n \t
- Why do severe spinal cord injuries usually cause paralysis?<\/li>\r\n \t
- What do you think are some possible consequences of severe damage to the brain stem? How might this compare to the consequences of severe damage to the frontal lobe? Explain your answer.<\/li>\r\n \t
- Information travels very quickly in the nervous system, but generally, the longer the path between areas, the longer it takes. Based on this, explain why you think reflexes often occur at the spinal cord level, and do not require input from the brain.<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
\r\n8.5 Explore More<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=sewhbmh0ECg\r\nWhat if we could look inside human brains? - Moran Cerf, TED-Ed, 2013.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=ZMSbDwpIyF4\r\n
The left brain vs. right brain myth - Elizabeth Waters, TED-Ed, 2017.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?time_continue=1&v=aCv4K5aStdU&feature=emb_logo\r\n
Split-brain patient 'Joe' being tested with stimuli presented in different visual fields,\r\nmarkmcdermott, 2010.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n
Attributes<\/h2>\r\nFigure 8.5.1<\/strong>\r\n\r\nSensory_Homunculus-en.svg<\/a> by Popadius<\/a> on Wikimedia Commons is used under a CC BY 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0\/deed.en) license. (This is a derivative work from File:1421 Sensory Homunculus<\/a>.jpg by OpenStax College<\/a>)\r\n\r\nFigure 8.5.2<\/strong>\r\n\r\nOverview_of_Nervous_System<\/a>\u00a0by OpenStax<\/a> on Wikimedia Commons is used under a CC BY 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en) license.\r\n\r\nFigure 8.5.3<\/strong>\r\n\r\nDiagram_showing_the_brain_stem_which_includes_the_medulla_oblongata,_the_pons_and_the_midbrain_(2)_CRUK_294.svg<\/a> by Cancer Research UK<\/a> on Wikimedia Commons is used under a CC BY-SA 4.0 <\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\nFigure 8.5.4<\/strong>\r\n\r\nBrain_bulbar_region.svg<\/a> by Fvasconcellos<\/a> on Wikimedia Commons is used under a CC BY 2.5<\/a> license (derivative work from Brain human sagittal section.svg<\/a>\u00a0 by Patrick J. Lynch; Brain bulbar region.PNG<\/a> by DO11.10<\/a>).\r\n\r\nFigure 8.5.5<\/strong>\r\n\r\nMidbrain<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY 3.0 <\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0) license.\r\n\r\nFigure 8.5.6<\/strong>\r\n\r\nBrainLobes<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY 3.0 <\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0) license.\u00a0<\/span>\r\n\r\nFigure 8.5.7<\/strong>\r\n\r\nDiencephalon<\/a> by OpenStax<\/a> Wikimedia Commons is used under a CC BY 4.0 <\/a>(https:\/\/creativecommons.org\/licenses\/by\/4.0) license.\r\n\r\nFigure 8.5.8<\/strong>\r\n\r\nSpinalCord<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY 3.0 <\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0) license.\u00a0<\/span>\r\n\r\nFigure 8.5.9<\/strong>\r\n\r\nSpinal_readjustment_3<\/a> by Tomwsulcer<\/a> on\u00a0 Wikimedia Commons is used under a CC0 1.0<\/a> Universal Public Domain Dedication license (https:\/\/creativecommons.org\/publicdomain\/zero\/1.0\/deed.en).\r\n\r\nFigure 8.5.10<\/strong>\r\n\r\n1507_Short_and_Long_Reflexes<\/a> by OpenStax<\/a> on Wikimedia Commons is used under a CC BY 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en) license.\r\nReferences<\/h2>\r\n
Betts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2013, 28 May). Figure 14.23<\/span>\u00a0<\/span>The sensory homunculus <\/span>[digital image]. In Anatomy and Physiology<\/em> (Section 14.2). OpenStax. https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/14-2-central-processing\r\n<\/span><\/span><\/p>\r\nBetts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2013, 28 May). Figure 15.8 Short and long reflexes [digital image]. In Anatomy and Physiology<\/em> (Section 15.2). OpenStax. https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/15-2-autonomic-reflexes-and-homeostasis<\/p>\r\nBetts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2016, May 18). <\/span><\/span>Figure 12.2 Central and peripheral nervous system [digital image]. In Anatomy and Physiology<\/em> (Section 12.1). https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/12-1-basic-structure-and-function-of-the-nervous-system<\/span><\/span><\/p>\r\nBetts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2016, May 18). Figure 13.11 The diencephalon [digital image]. In Anatomy and Physiology<\/em> (Section 13.2). https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/13-2-the-central-nervous-system<\/p>\r\nBlausen.com staff. (2014). Medical gallery of Blausen Medical 2014. WikiJournal of Medicine,<\/em> 1<\/em> (2). DOI:10.15347\/wjm\/2014.010. ISSN 2002-4436<\/span><\/p>\r\nmarkmcdermott. (2010). Split-brain patient 'Joe' being tested with stimuli presented in different visual fields. YouTube. https:\/\/www.youtube.com\/user\/markmcdermott\/search?query=split<\/p>\r\n
Mayo Clinic Staff. (n.d.). Stroke [online article]. MayoClinic.org. https:\/\/www.mayoclinic.org\/diseases-conditions\/stroke\/symptoms-causes\/syc-20350113<\/p>\r\n
Soton Brain Hub. (2016, July 29). The limbic system. YouTube. https:\/\/www.youtube.com\/watch?v=jcrWPo_s6EE&feature=youtu.be<\/p>\r\n
TED-Ed. (2013, January 31). What if we could look inside human brains? - Moran Cerf. YouTube. https:\/\/www.youtube.com\/watch?v=sewhbmh0ECg&feature=youtu.be<\/p>\r\n
TED-Ed. (2017, July 24). The left brain vs. right brain myth - Elizabeth Waters. YouTube. https:\/\/www.youtube.com\/watch?v=ZMSbDwpIyF4&feature=youtu.be<\/p>\r\n ","rendered":"
<\/p>\nFigure 8.5.1 This picture is called an <\/em>homunculus.\u00a0<\/em><\/figcaption><\/figure>\nHomunculus<\/h1>\n
The very odd-looking drawing in Figure 8.5.1 is called a homunculus. The beige mass represents a cross-sectional wedge of the human brain, and the drawing shows some areas of the brain associated with different parts of the body. As you can see, larger areas of the brain in this region are associated with the hands, face, and tongue, as compared to the areas associated with the legs and feet. Given the importance of speech, manual dexterity, and face-to-face social interactions in human beings, it is not surprising that relatively large areas of the brain are needed to control these body parts. The brain is the most complex organ in the human body and part of the central nervous system.<\/p>\n
\nWhat Is the Central Nervous System?<\/h1>\n<\/div>\n
The central nervous system<\/a> (CNS) is the part of the nervous system that includes the brain<\/a> and spinal cord<\/a>. The drawing below (Figure 8.5.2) shows the central nervous system as one of two main divisions of the total nervous system. The other main division is the peripheral nervous system<\/a> (PNS). The CNS and PNS work together to control virtually all body functions.<\/p>\nFigure 8.5.2 The two main divisions of the nervous system: the central nervous system (CNS) \u2014 which includes the brain and spinal cord \u2014 and the peripheral nervous system (PNS), which includes nerves and ganglia (singular, ganglion), which transmit information between the CNS to the rest of the body.<\/em><\/figcaption><\/figure>\nThe delicate nervous tissues of the central nervous system are protected by major physical and chemical barriers. Physically, the brain and spinal cord are surrounded by tough meninges<\/a>, a three-layer protective sheath that also contains cushioning cerebrospinal fluid<\/a>. The\u00a0bones\u00a0of the skull and spinal vertebrae also contribute to physically protecting the brain and spinal cord. Chemically, the brain and spinal cord are isolated from the circulation\u00a0\u2014\u00a0and most toxins or pathogens in the\u00a0blood\u00a0\u2014\u00a0by the\u00a0blood-brain barrier<\/a>.<\/strong>\u00a0The blood-brain barrier is a highly selective membrane formed of endothelial\u00a0cells\u00a0that separates the circulating\u00a0blood\u00a0from extracellular fluid in the CNS. The barrier allows\u00a0water, certain gases, glucose, and some other molecules needed by the brain and spinal cord to cross from the blood into the CNS, while keeping out potentially harmful substances. These physical and chemical barriers make the CNS less susceptible to injury than the PNS. However, damage to the CNS is likely to have more serious consequences.<\/p>\n\nThe Brain<\/h1>\n<\/div>\n
The\u00a0brain<\/a><\/strong> is the control center of not only the rest of the nervous system, but of the entire organism. The adult brain makes up only about 2% of the body\u2019s weight, but it uses about 20% of the body\u2019s total energy. The brain contains an estimated 100 billion neurons, and each neuron<\/a> has thousands of synaptic connections to other neurons. The brain also has about the same number of neuroglia<\/a> as neurons. No wonder the brain uses so much energy! In addition, the brain uses mostly glucose<\/a> for energy. As a result, if the brain is deprived of glucose, it can lead to unconsciousness. The brain is able to store some glucose in the form of glycogen, but in much smaller amounts than are found in the liver and skeletal muscles.<\/p>\nThe brain controls such mental processes as reasoning, imagination, memory, and language. It also interprets information from the senses and commands the body to respond appropriately. It controls basic physical processes (such as breathing and heartbeat), as well as voluntary activities (such as walking and writing). The brain has three major regions: the hindbrain, the midbrain and the forebrain. These parts are shown in Figure 8.5.3 and described below.<\/p>\nFigure 8.5.3 Diagram of the forebrain, midbrain and hindbrain. <\/em><\/figcaption><\/figure>\n\n <\/p>\n<\/div>\n
The Hindbrain<\/h2>\nFigure 8.5.4 The hindbrain consists of the cerebellum,<\/em> medulla oblongata, and the pons. It plays the extremely important role of connecting the brain to the rest of the body via the spinal cord.<\/em><\/figcaption><\/figure>\nThe\u00a0hindbrain<\/a>, <\/strong>which includes the cerebellum<\/a>, medulla oblongata<\/a>, and the pons<\/a>. The hindbrain is the lowest part of the brain. It resembles a stalk and platform on which the cerebrum is perched. The components of the hindbrain connect the rest of the brain with the spinal cord and passes nerve impulses between the brain and spinal cord.<\/p>\nCerebellum<\/h3>\n
The\u00a0cerebellum<\/a><\/strong> is located just below the cerebrum and at the back of the brain behind the brain stem. It coordinates your voluntary movements, balance, and posture.\u00a0 Information from your inner ear, joints and muscles, and eyes are all knitted together in the cerebellum so that you have awareness of where you are in 3-dimensional space.\u00a0 Patients who have suffered damage to their cerebellum may suffer from balance disorder. In addition the cerebellum plays a major role in motor learning (like how to ride a bike or how to do a backflip on a trampoline) through trial and error.\u00a0 While traditionally, the cerebellum was thought to only be involved in motor functions, we now know that it also plays an important role in memory and learning.<\/p>\nMedulla Oblongata<\/h3>\n
The\u00a0medulla oblongata<\/a><\/strong> makes up part of the brainstem and sits in front of and just below the cerebellum, at the very top of the spinal cord.\u00a0 It is responsible for control of heart rate, respiration rate and blood pressure, as well as reflexes such as vomiting, coughing, sneezing and swallowing.<\/p>\nPons<\/h3>\n
The\u00a0pons<\/a><\/strong> is located in front of the cerebellum and above the medulla oblongata.\u00a0 It has several functions, including receiving sensory information from the face, regulating rate and depth of breaths, as well as sleep cycles.<\/p>\nMidbrain<\/h2>\nFigure 8.5.5 The brainstem includes the midbrain, the pons and the medulla oblongata.<\/em><\/figcaption><\/figure>\nThe midbrain is the topmost part of the brainstem and is the essential connection between and brain and spinal cord.\u00a0 The three main parts of the midbrain are the colliculi, the tegmentum, and the cerebral peduncles.\u00a0 These structures are all considered part of the brainstem, which consists of the medulla oblongata, the pons and the midbrain.<\/p>\n
Reticular Activating System<\/h3>\n
The reticular activating system<\/a> (RAS) is responsible for the sleep-wake cycle and wakefulness.\u00a0 It also regulates attention, ability to focus and arousal.<\/p>\nForebrain<\/h2>\n
The forebrain is the anterior (forwardmost) part of the brain and includes the cerebrum, the thalamus and hypothalamus, hippocampus, amygdala, and limbic system.\u00a0 This portion of the brain is responsible for processing incoming sensory information, performing complex cognitive activities (speech, abstract thought, etc) and governing voluntary motor movements.\u00a0 \u00a0The forebrain also controls body temperature, reproductive functions, eating, sleeping and the display of emotions.<\/p>\n
Cerebrum<\/h3>\n
The\u00a0cerebrum<\/a><\/strong>\u00a0is the largest part of the brain. It controls conscious, intellectual functions.\u00a0Among other things,\u00a0it controls reasoning, language, memory, sight, touch, and hearing. When you read a book, play a video game, or recognize a classmate, you are using your cerebrum.<\/p>\nHemispheres and Lateralization of the Cerebrum<\/h4>\n
The cerebrum is divided from front to back into two halves called the left and right\u00a0hemispheres<\/a>.<\/strong>\u00a0The two hemispheres are connected by a thick bundle of axons, known as the corpus callosum<\/a>, which lies deep within the brain. The corpus callosum is the main avenue of\u00a0communication between the two hemispheres. It connects each point in the cerebrum to the mirror-image point in the opposite hemisphere.<\/p>\nThe right and left hemispheres of the cerebrum are similar in shape, and most areas of cerebrum are found in both hemispheres. Some areas, however, show\u00a0lateralization<\/a>,<\/strong>\u00a0or a\u00a0concentration\u00a0in one hemisphere or the other.\u00a0In most people, for example, language functions are more concentrated in the left hemisphere, whereas abstract reasoning and visual-spatial abilities are more concentrated in the right hemisphere.<\/p>\nFor reasons that are not yet clear, each hemisphere of the brain interacts primarily with the opposite side of the body. The left side of the brain receives messages from and sends commands to the right side of the body, and the right side of the brain\u00a0receives messages from and sends commands to the left side of the body. Sensory nerves from the spinal cord to the brain and motor nerves from the brain to the spinal cord both cross the midline of the body at the level of the brain stem.<\/p>\n
Lobes of the Cerebrum<\/h4>\n
Each hemisphere<\/a> of the cerebrum is further divided into the four lobes shown in Figure 8.5.6 and described below.<\/p>\nFigure 8.5.6 The cerebrum is organized into four lobes: frontal, parietal, occipital, and temporal.<\/em><\/figcaption><\/figure>\n\nEach hemisphere of the cerebrum consists of four parts, called lobes. Each lobe is associated with particular brain functions. Just one function of each lobe is listed here.<\/p>\n<\/div>\n
\n- The\u00a0frontal lobes<\/a><\/strong>\u00a0are located at the front of the brain behind the forehead. The frontal lobes are associated with executive functions, such as attention, self-control, planning, problem solving, reasoning, abstract thought, language, and personality.<\/li>\n
- The\u00a0parietal lobes<\/a><\/strong>\u00a0are located behind the frontal lobes at the top of the head. The parietal lobes are involved in sensation \u2014 including\u00a0temperature, touch, and taste. Reading and arithmetic are also functions of the parietal lobes.<\/li>\n
- The\u00a0temporal lobes<\/a><\/strong>\u00a0are located at the sides of the head below the frontal and parietal lobes. The temporal lobes enable hearing, the formation and retrieval of memories, and the integration of memories and sensations.<\/li>\n
- The\u00a0occipital lobes<\/a><\/strong>\u00a0are located at the back of the head below the parietal lobes. The occipital lobes are the smallest of the four pairs of lobes. They are dedicated almost solely to\u00a0vision.<\/li>\n<\/ul>\n
Cerebral Cortex<\/h4>\n
Most of the information processing in the brain actually takes place in the\u00a0cerebral cortex<\/a><\/strong>, a rind of gray matter and other tissues just a few millimetres thick that makes up the outer surface of the cerebrum in both hemispheres of the brain. The cerebral cortex has many folds in it, greatly increasing the amount of surface area of the brain that can fit within the skull. Because of all the folds in the human cerebral cortex, it has a surface area of about 2,500 cm2<\/sup>\u00a0(2.5 ft2<\/sup>). The size and importance of the cerebral cortex is far greater in the human brain than the brains of any other vertebrates, including nonhuman\u00a0primates.<\/p>\nThe Limbic System<\/h3>\n
The limbic system consists of the hypothalamus, thalamus, the hippocampus and amygdala. The structures and interacting areas of the\u00a0limbic system<\/a><\/b>\u00a0are involved in motivation, emotion, learning, and memory.<\/p>\nThalamus and Hypothalamus<\/h4>\n
Several structures are located deep within the brain and are important for communication between the brain and spinal cord (or the rest of the body). These structures include the hypothalamus and thalamus. The diagram below (Figure 8.5.7) shows where these structures are located in the brain. Like the two halves of the cerebrum, the hypothalamus and thalamus exist in two halves, one in each hemisphere.<\/p>\nFigure 8.5.7 Structures deep within the brain include the hypothalamus and thalamus.<\/em><\/figcaption><\/figure>\nThe\u00a0hypothalamus<\/a><\/strong>\u00a0is located just above the brain stem, and is about the size of an almond. The hypothalamus is responsible for certain metabolic processes and other activities of the autonomic nervous system<\/a>, including body\u00a0temperature,\u00a0heart\u00a0rate, hunger, thirst, fatigue, sleep, wakefulness, and circadian (24-hour) rhythms. The hypothalamus is also an important emotional center of the brain. The hypothalamus can regulate so many body functions because it responds to many different internal and external signals, including messages from the brain, light, steroid hormones, stress, and invading pathogens, among others.<\/p>\nOne way the hypothalamus influences body functions is by synthesizing hormones that directly influence body processes. It synthesizes the hormone oxytocin<\/a>, which stimulates uterine contractions during childbirth and the letdown of milk during lactation. It also synthesizes antidiuretic hormone<\/a>, which stimulates the kidneys to reabsorb more water and excrete more concentrated urine. These two hormones are sent from the hypothalamus via a stalk-like structure called the infundibulum (see Figure 8.5.7) directly to the posterior (back) portion of the pituitary gland, which secretes them into the blood.<\/p>\nThe main way the hypothalamus influences body functions is by controlling the\u00a0pituitary gland<\/a>, known as the master gland of the\u00a0endocrine system. The hypothalamus synthesizes neurohormones called releasing factors that travel through the infundibulum directly to the anterior (front) part of the pituitary gland. The releasing factors generally either stimulate or inhibit the secretion of anterior pituitary hormones, most of which control other glands of the endocrine system.<\/p>\n
The Hindbrain<\/h2>\r\n[caption id=\"attachment_3077\" align=\"alignright\" width=\"367\"] Figure 8.5.4 The hindbrain consists of the cerebellum,<\/em> medulla oblongata, and the pons. It plays the extremely important role of connecting the brain to the rest of the body via the spinal cord.<\/em>[\/caption]\r\n\r\nThe\u00a0[pb_glossary id=\"3073\"]hindbrain[\/pb_glossary], <\/strong>which includes the [pb_glossary id=\"5935\"]cerebellum[\/pb_glossary], [pb_glossary id=\"3075\"]medulla oblongata[\/pb_glossary], and the [pb_glossary id=\"3076\"]pons[\/pb_glossary]. The hindbrain is the lowest part of the brain. It resembles a stalk and platform on which the cerebrum is perched. The components of the hindbrain connect the rest of the brain with the spinal cord and passes nerve impulses between the brain and spinal cord.\r\nCerebellum<\/h3>\r\nThe\u00a0[pb_glossary id=\"5935\"]cerebellum[\/pb_glossary]<\/strong> is located just below the cerebrum and at the back of the brain behind the brain stem. It coordinates your voluntary movements, balance, and posture.\u00a0 Information from your inner ear, joints and muscles, and eyes are all knitted together in the cerebellum so that you have awareness of where you are in 3-dimensional space.\u00a0 Patients who have suffered damage to their cerebellum may suffer from balance disorder. In addition the cerebellum plays a major role in motor learning (like how to ride a bike or how to do a backflip on a trampoline) through trial and error.\u00a0 While traditionally, the cerebellum was thought to only be involved in motor functions, we now know that it also plays an important role in memory and learning.\r\nMedulla Oblongata<\/h3>\r\nThe\u00a0[pb_glossary id=\"3075\"]medulla oblongata[\/pb_glossary]<\/strong> makes up part of the brainstem and sits in front of and just below the cerebellum, at the very top of the spinal cord.\u00a0 It is responsible for control of heart rate, respiration rate and blood pressure, as well as reflexes such as vomiting, coughing, sneezing and swallowing.\r\nPons<\/h3>\r\nThe\u00a0[pb_glossary id=\"3076\"]pons[\/pb_glossary]<\/strong> is located in front of the cerebellum and above the medulla oblongata.\u00a0 It has several functions, including receiving sensory information from the face, regulating rate and depth of breaths, as well as sleep cycles.\r\nMidbrain<\/h2>\r\n[caption id=\"attachment_3079\" align=\"alignleft\" width=\"317\"] Figure 8.5.5 The brainstem includes the midbrain, the pons and the medulla oblongata.<\/em>[\/caption]\r\n\r\nThe midbrain is the topmost part of the brainstem and is the essential connection between and brain and spinal cord.\u00a0 The three main parts of the midbrain are the colliculi, the tegmentum, and the cerebral peduncles.\u00a0 These structures are all considered part of the brainstem, which consists of the medulla oblongata, the pons and the midbrain.\r\nReticular Activating System<\/h3>\r\nThe [pb_glossary id=\"3082\"]reticular activating system[\/pb_glossary] (RAS) is responsible for the sleep-wake cycle and wakefulness.\u00a0 It also regulates attention, ability to focus and arousal.\r\nForebrain<\/h2>\r\nThe forebrain is the anterior (forwardmost) part of the brain and includes the cerebrum, the thalamus and hypothalamus, hippocampus, amygdala, and limbic system.\u00a0 This portion of the brain is responsible for processing incoming sensory information, performing complex cognitive activities (speech, abstract thought, etc) and governing voluntary motor movements.\u00a0 \u00a0The forebrain also controls body temperature, reproductive functions, eating, sleeping and the display of emotions.\r\nCerebrum<\/h3>\r\nThe\u00a0[pb_glossary id=\"5941\"]cerebrum[\/pb_glossary]<\/strong>\u00a0is the largest part of the brain. It controls conscious, intellectual functions.\u00a0Among other things,\u00a0it controls reasoning, language, memory, sight, touch, and hearing. When you read a book, play a video game, or recognize a classmate, you are using your cerebrum.\r\nHemispheres and Lateralization of the Cerebrum<\/h4>\r\nThe cerebrum is divided from front to back into two halves called the left and right\u00a0[pb_glossary id=\"3083\"]hemispheres[\/pb_glossary].<\/strong>\u00a0The two hemispheres are connected by a thick bundle of axons, known as the [pb_glossary id=\"5955\"]corpus callosum[\/pb_glossary], which lies deep within the brain. The corpus callosum is the main avenue of\u00a0communication between the two hemispheres. It connects each point in the cerebrum to the mirror-image point in the opposite hemisphere.\r\n\r\nThe right and left hemispheres of the cerebrum are similar in shape, and most areas of cerebrum are found in both hemispheres. Some areas, however, show\u00a0[pb_glossary id=\"3085\"]lateralization[\/pb_glossary],<\/strong>\u00a0or a\u00a0concentration\u00a0in one hemisphere or the other.\u00a0In most people, for example, language functions are more concentrated in the left hemisphere, whereas abstract reasoning and visual-spatial abilities are more concentrated in the right hemisphere.\r\n\r\nFor reasons that are not yet clear, each hemisphere of the brain interacts primarily with the opposite side of the body. The left side of the brain receives messages from and sends commands to the right side of the body, and the right side of the brain\u00a0receives messages from and sends commands to the left side of the body. Sensory nerves from the spinal cord to the brain and motor nerves from the brain to the spinal cord both cross the midline of the body at the level of the brain stem.\r\nLobes of the Cerebrum<\/h4>\r\nEach [pb_glossary id=\"3083\"]hemisphere[\/pb_glossary] of the cerebrum is further divided into the four lobes shown in Figure 8.5.6 and described below.\r\n\r\n[caption id=\"attachment_3086\" align=\"aligncenter\" width=\"680\"] Figure 8.5.6 The cerebrum is organized into four lobes: frontal, parietal, occipital, and temporal.<\/em>[\/caption]\r\n\r\n\r\n\r\nEach hemisphere of the cerebrum consists of four parts, called lobes. Each lobe is associated with particular brain functions. Just one function of each lobe is listed here.\r\n\r\n<\/div>\r\n\r\n \t- The\u00a0[pb_glossary id=\"6021\"]frontal lobes[\/pb_glossary]<\/strong>\u00a0are located at the front of the brain behind the forehead. The frontal lobes are associated with executive functions, such as attention, self-control, planning, problem solving, reasoning, abstract thought, language, and personality.<\/li>\r\n \t
- The\u00a0[pb_glossary id=\"3088\"]parietal lobes[\/pb_glossary]<\/strong>\u00a0are located behind the frontal lobes at the top of the head. The parietal lobes are involved in sensation \u2014 including\u00a0temperature, touch, and taste. Reading and arithmetic are also functions of the parietal lobes.<\/li>\r\n \t
- The\u00a0[pb_glossary id=\"3089\"]temporal lobes[\/pb_glossary]<\/strong>\u00a0are located at the sides of the head below the frontal and parietal lobes. The temporal lobes enable hearing, the formation and retrieval of memories, and the integration of memories and sensations.<\/li>\r\n \t
- The\u00a0[pb_glossary id=\"3090\"]occipital lobes[\/pb_glossary]<\/strong>\u00a0are located at the back of the head below the parietal lobes. The occipital lobes are the smallest of the four pairs of lobes. They are dedicated almost solely to\u00a0vision.<\/li>\r\n<\/ul>\r\n
Cerebral Cortex<\/h4>\r\nMost of the information processing in the brain actually takes place in the\u00a0[pb_glossary id=\"5937\"]cerebral cortex[\/pb_glossary]<\/strong>, a rind of gray matter and other tissues just a few millimetres thick that makes up the outer surface of the cerebrum in both hemispheres of the brain. The cerebral cortex has many folds in it, greatly increasing the amount of surface area of the brain that can fit within the skull. Because of all the folds in the human cerebral cortex, it has a surface area of about 2,500 cm2<\/sup>\u00a0(2.5 ft2<\/sup>). The size and importance of the cerebral cortex is far greater in the human brain than the brains of any other vertebrates, including nonhuman\u00a0primates.\r\nThe Limbic System<\/h3>\r\nThe limbic system consists of the hypothalamus, thalamus, the hippocampus and amygdala. The structures and interacting areas of the\u00a0[pb_glossary id=\"3098\"]limbic system[\/pb_glossary]<\/b>\u00a0are involved in motivation, emotion, learning, and memory.\r\nThalamus and Hypothalamus<\/h4>\r\nSeveral structures are located deep within the brain and are important for communication between the brain and spinal cord (or the rest of the body). These structures include the hypothalamus and thalamus. The diagram below (Figure 8.5.7) shows where these structures are located in the brain. Like the two halves of the cerebrum, the hypothalamus and thalamus exist in two halves, one in each hemisphere.\r\n\r\n[caption id=\"attachment_3092\" align=\"alignleft\" width=\"363\"] Figure 8.5.7 Structures deep within the brain include the hypothalamus and thalamus.<\/em>[\/caption]\r\n\r\nThe\u00a0[pb_glossary id=\"2937\"]hypothalamus[\/pb_glossary]<\/strong>\u00a0is located just above the brain stem, and is about the size of an almond. The hypothalamus is responsible for certain metabolic processes and other activities of the [pb_glossary id=\"5899\"]autonomic nervous system[\/pb_glossary], including body\u00a0temperature,\u00a0heart\u00a0rate, hunger, thirst, fatigue, sleep, wakefulness, and circadian (24-hour) rhythms. The hypothalamus is also an important emotional center of the brain. The hypothalamus can regulate so many body functions because it responds to many different internal and external signals, including messages from the brain, light, steroid hormones, stress, and invading pathogens, among others.\r\n\r\nOne way the hypothalamus influences body functions is by synthesizing hormones that directly influence body processes. It synthesizes the hormone [pb_glossary id=\"3093\"]oxytocin[\/pb_glossary], which stimulates uterine contractions during childbirth and the letdown of milk during lactation. It also synthesizes [pb_glossary id=\"5893\"]antidiuretic hormone[\/pb_glossary], which stimulates the kidneys to reabsorb more water and excrete more concentrated urine. These two hormones are sent from the hypothalamus via a stalk-like structure called the infundibulum (see Figure 8.5.7) directly to the posterior (back) portion of the pituitary gland, which secretes them into the blood.\r\n\r\nThe main way the hypothalamus influences body functions is by controlling the\u00a0[pb_glossary id=\"2938\"]pituitary gland[\/pb_glossary], known as the master gland of the\u00a0endocrine system. The hypothalamus synthesizes neurohormones called releasing factors that travel through the infundibulum directly to the anterior (front) part of the pituitary gland. The releasing factors generally either stimulate or inhibit the secretion of anterior pituitary hormones, most of which control other glands of the endocrine system.\r\n\r\nThe\u00a0[pb_glossary id=\"3095\"]thalamus[\/pb_glossary],<\/strong> which is located near the hypothalamus (see Figure 8.5.7), is a major hub for information traveling back and forth between the spinal cord and cerebrum. It relays sensory signals to the cerebral cortex and motor signals to the spinal cord. It is also involved in the regulation of consciousness, sleep, and alertness.\r\n\r\nHippocampus and Amygdala<\/h4>\r\nThe [pb_glossary id=\"3096\"]hippocampus[\/pb_glossary] is a complex structure embedded deep in the temporal lobe.\u00a0 It plays a major role in learning and memory and contributes to regulation of motivation and emotion. The amygdala is the part of the brain responsible for formation and storage of memories associated with emotional events.\r\n\r\nWatch \"The Limbic System\" by Soton Brain Hub to learn about the location and functions of the limbic system.\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=jcrWPo_s6EE\r\n
The Limbic System, Soton Brain Hub, 2016.<\/p>\r\n\r\n
Spinal Cord<\/h1>\r\n<\/div>\r\nThe\u00a0[pb_glossary id=\"3010\"]spinal cord[\/pb_glossary]<\/strong> is a long, thin, tubular bundle of nervous tissues that extends from the brain stem and continues down the center of the back to the pelvis. It is highlighted in yellow in Figure 8.5.8. The spinal cord is enclosed within, but is shorter than, the vertebral column.\r\n\r\n[caption id=\"attachment_3099\" align=\"alignnone\" width=\"482\"] Figure 8.5.8 The spinal cord (yellow) runs from the bottom of the brain to the lower back.<\/em>[\/caption]\r\nStructure of the Spinal Cord<\/h2>\r\nThe center of the spinal cord consists of gray matter, which is made up mainly of cell bodies of neurons, including interneurons and motor neurons. The gray matter is surrounded by white matter that consists mainly of myelinated axons of motor and sensory neurons. Spinal nerves, which connect the spinal cord to the PNS, exit from the spinal cord between vertebrae (see Figure 8.5.9).\r\n\r\n \r\n\r\n\r\n[caption id=\"attachment_3100\" align=\"alignleft\" width=\"291\"] Figure 8.5.9 This model shows three vertebrae (white) with branching spinal nerves (yellow) emerging from the either side of the spinal cord between vertebrae.<\/em>[\/caption]\r\n\r\n<\/div>\r\nFunctions of the Spinal Cord<\/h2>\r\nThe spinal cord serves as an information superhighway. It passes messages from the body to the brain and from the brain to the body. Sensory (afferent) nerves carry\u00a0nerve impulses\u00a0to the brain from sensory receptor\u00a0cells\u00a0everywhere in and on the body. Motor (efferent) nerves carry nerve impulses away from the brain to glands, organs, or\u00a0muscles throughout the body.\r\n\r\nThe spinal cord also independently controls certain rapid responses called\u00a0reflexes<\/strong> without any input from the brain. You can see how this may happen in Figure 8.5.10. A sensory receptor responds to a sensation and sends a nerve impulse along a sensory nerve to the spinal cord. In the spinal cord, the message passes to an interneuron and from the interneuron to a motor nerve, which carries the impulse to a muscle. The muscle contracts in response. These neuron connections form a reflex arc, which requires no input from the brain. No doubt you have experienced such reflex actions yourself. For example, you may have reached out to touch a pot on the stove, not realizing that it was very hot. Virtually at the same moment that you feel the burning heat, you jerk your arm back and remove your hand from the pot.\r\n\r\n \r\n\r\n\r\n[caption id=\"attachment_3101\" align=\"alignnone\" width=\"1038\"] Figure 8.5.10 This diagram shows what happens in a long reflex (top), in which sensory nerves carry the message all the way to the spinal cord; and in a short reflex (bottom), in which sensory nerves travel only to a ganglion outside the spinal cord. Note that interneurons are involved in reflexes, connecting sensory and motor neurons, but they are not actually shown in the diagram.<\/em>[\/caption]\r\n\r\n<\/div>\r\nInjuries to the Spinal Cord<\/h2>\r\nPhysical damage to the spinal cord may result in\u00a0[pb_glossary id=\"3102\"]paralysis[\/pb_glossary],<\/strong> which is loss of sensation and movement in part of the body. Paralysis generally affects all the areas of the body below the level of the injury, because nerve impulses are interrupted and can no longer travel back and forth between the brain and body beyond that point. If an injury to the spinal cord produces nothing more than swelling, the symptoms may be transient. However, if nerve fibres (axons) in the spinal cord are badly damaged, the loss of function may be permanent. Experimental studies have shown that spinal nerve fibres attempt to regrow, but tissue destruction usually produces scar tissue that cannot be penetrated by the regrowing nerves, as well other factors that inhibit nerve fibre regrowth in the central nervous system.\r\n\r\nFeature: My\u00a0Human Body<\/h1>\r\n<\/div>\r\nEach year, many millions of people have a stroke<\/a>, and stroke is the second leading cause of death in adults.\u00a0[pb_glossary id=\"3103\"]Stroke[\/pb_glossary],<\/strong>\u00a0also known as cerebrovascular accident, occurs when poor blood flow to the brain results in the death of brain cells. There are two main types of strokes:\r\n\r\n \t- Ischemic strokes occur due to lack of blood flow because of a blood clot in an artery going to the brain.<\/li>\r\n \t
- Hemorrhagic strokes occur due to bleeding from a broken blood vessel in the brain.<\/li>\r\n<\/ul>\r\nEither type of stroke may result in paralysis, loss of the ability to speak or comprehend speech, loss of bladder control, personality changes, and many other potential effects, depending on the part of the brain that is injured. The effects of a stroke may be mild and transient or more severe and permanent. A stroke may even be fatal. It generally depends on the type of stroke and how extensive it is.\r\n\r\nAre you at risk of a stroke? The main risk factor for stroke is age \u2014 about two-thirds of strokes occur in people over the age of 65. There is nothing you can do about your age, but most other stroke risk factors can be reduced with lifestyle changes or medications. The risk factors include high blood pressure, tobacco smoking, obesity, high blood cholesterol, diabetes mellitus, and atrial fibrillation.\r\n\r\nChances are good that you or someone you know is at risk of a stroke, so it is important to recognize a stroke if one occurs. A stroke is a medical emergency, and the more quickly treatment is given, the better the outcome is likely to be. In the case of ischemic strokes, the use of clot-busting drugs may prevent permanent brain damage if administered within three or four hours of the stroke. Remembering the signs of a stroke is easy. They are summed up by the acronym FAST.\r\n\r\n
\r\n8.5 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- The [pb_glossary id=\"5933\"]central nervous system[\/pb_glossary] is the part of the nervous system that includes the [pb_glossary id=\"5915\"]brain[\/pb_glossary] and [pb_glossary id=\"3010\"]spinal cord[\/pb_glossary]. It is physically protected by\u00a0bones, meninges, and [pb_glossary id=\"5939\"]cerebrospinal fluid[\/pb_glossary]. It is chemically protected by the blood-brain barrier.<\/li>\r\n \t
- The brain is the control center of the nervous system and of the entire organism. The brain uses a relatively large proportion of the body\u2019s\u00a0energy, primarily in the form of glucose.<\/li>\r\n \t
- The brain is divided into three major parts, each with different functions: the hindbrain, the midbrain and the forebrain.<\/li>\r\n \t
- Hindbrain consists of the medulla oblongata, the pons and the cerebellum, each of which perform specific functions.<\/li>\r\n \t
- The midbrain is primarily responsible for motor movement and in auditory and visual processing.<\/li>\r\n \t
- The forebrain contains many structures including:\r\n
\r\n \t- The cerebrum, which is further divided into left and right hemispheres. Each hemisphere has four lobes: frontal, parietal, temporal, and occipital. Each lobe is associated with specific senses or other functions.<\/li>\r\n \t
- The cerebrum\u00a0has a\u00a0thin outer layer called the cerebral cortex. Its many folds give it a large surface area. This is where most information processing takes place.<\/li>\r\n \t
- Inner structures of the brain include the hypothalamus \u2014 which controls the\u00a0endocrine system\u00a0via the\u00a0pituitary gland\u00a0\u2014 and the thalamus, which has several involuntary functions.<\/li>\r\n \t
- The hippocampus and amygdala, which are part of the limbic system and play important roles in memory, learning and emotions.<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t
- The spinal cord is a tubular bundle of nervous tissues that extends from the head down the middle of the back to the pelvis. It functions mainly to connect the brain with the\u00a0peripheral nervous system. It also controls certain rapid responses called reflexes without any input from the brain.<\/li>\r\n \t
- A spinal cord injury may lead to paralysis (loss of sensation and movement) of the body below the level of the injury, because nerve impulses can no longer travel up and down the spinal cord beyond that point.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n8.5 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- What is the central nervous system?<\/li>\r\n \t
- How is the central nervous system protected?<\/li>\r\n \t
- What is the overall function of the brain?<\/li>\r\n \t
- Identify the three main parts of the brain and one function of each part.<\/li>\r\n \t
- Describe the hemispheres of the brain.<\/li>\r\n \t
- Explain and give examples of lateralization of the brain.<\/li>\r\n \t
- Identify one function of each of the four lobes of the cerebrum.<\/li>\r\n \t
- [h5p id=\"562\"]<\/li>\r\n \t
- [h5p id=\"563\"]<\/li>\r\n \t
- Summarize the structure and function of the cerebral cortex. Explain how the hypothalamus controls the endocrine system.<\/li>\r\n \t
- Describe the spinal cord.<\/li>\r\n \t
- What is the main function of the spinal cord?<\/li>\r\n \t
- Explain how reflex actions occur.<\/li>\r\n \t
- Why do severe spinal cord injuries usually cause paralysis?<\/li>\r\n \t
- What do you think are some possible consequences of severe damage to the brain stem? How might this compare to the consequences of severe damage to the frontal lobe? Explain your answer.<\/li>\r\n \t
- Information travels very quickly in the nervous system, but generally, the longer the path between areas, the longer it takes. Based on this, explain why you think reflexes often occur at the spinal cord level, and do not require input from the brain.<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
\r\n8.5 Explore More<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=sewhbmh0ECg\r\nWhat if we could look inside human brains? - Moran Cerf, TED-Ed, 2013.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=ZMSbDwpIyF4\r\n
The left brain vs. right brain myth - Elizabeth Waters, TED-Ed, 2017.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?time_continue=1&v=aCv4K5aStdU&feature=emb_logo\r\n
Split-brain patient 'Joe' being tested with stimuli presented in different visual fields,\r\nmarkmcdermott, 2010.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n
Attributes<\/h2>\r\nFigure 8.5.1<\/strong>\r\n\r\nSensory_Homunculus-en.svg<\/a> by Popadius<\/a> on Wikimedia Commons is used under a CC BY 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0\/deed.en) license. (This is a derivative work from File:1421 Sensory Homunculus<\/a>.jpg by OpenStax College<\/a>)\r\n\r\nFigure 8.5.2<\/strong>\r\n\r\nOverview_of_Nervous_System<\/a>\u00a0by OpenStax<\/a> on Wikimedia Commons is used under a CC BY 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en) license.\r\n\r\nFigure 8.5.3<\/strong>\r\n\r\nDiagram_showing_the_brain_stem_which_includes_the_medulla_oblongata,_the_pons_and_the_midbrain_(2)_CRUK_294.svg<\/a> by Cancer Research UK<\/a> on Wikimedia Commons is used under a CC BY-SA 4.0 <\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\nFigure 8.5.4<\/strong>\r\n\r\nBrain_bulbar_region.svg<\/a> by Fvasconcellos<\/a> on Wikimedia Commons is used under a CC BY 2.5<\/a> license (derivative work from Brain human sagittal section.svg<\/a>\u00a0 by Patrick J. Lynch; Brain bulbar region.PNG<\/a> by DO11.10<\/a>).\r\n\r\nFigure 8.5.5<\/strong>\r\n\r\nMidbrain<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY 3.0 <\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0) license.\r\n\r\nFigure 8.5.6<\/strong>\r\n\r\nBrainLobes<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY 3.0 <\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0) license.\u00a0<\/span>\r\n\r\nFigure 8.5.7<\/strong>\r\n\r\nDiencephalon<\/a> by OpenStax<\/a> Wikimedia Commons is used under a CC BY 4.0 <\/a>(https:\/\/creativecommons.org\/licenses\/by\/4.0) license.\r\n\r\nFigure 8.5.8<\/strong>\r\n\r\nSpinalCord<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY 3.0 <\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0) license.\u00a0<\/span>\r\n\r\nFigure 8.5.9<\/strong>\r\n\r\nSpinal_readjustment_3<\/a> by Tomwsulcer<\/a> on\u00a0 Wikimedia Commons is used under a CC0 1.0<\/a> Universal Public Domain Dedication license (https:\/\/creativecommons.org\/publicdomain\/zero\/1.0\/deed.en).\r\n\r\nFigure 8.5.10<\/strong>\r\n\r\n1507_Short_and_Long_Reflexes<\/a> by OpenStax<\/a> on Wikimedia Commons is used under a CC BY 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en) license.\r\nReferences<\/h2>\r\n
Betts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2013, 28 May). Figure 14.23<\/span>\u00a0<\/span>The sensory homunculus <\/span>[digital image]. In Anatomy and Physiology<\/em> (Section 14.2). OpenStax. https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/14-2-central-processing\r\n<\/span><\/span><\/p>\r\nBetts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2013, 28 May). Figure 15.8 Short and long reflexes [digital image]. In Anatomy and Physiology<\/em> (Section 15.2). OpenStax. https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/15-2-autonomic-reflexes-and-homeostasis<\/p>\r\nBetts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2016, May 18). <\/span><\/span>Figure 12.2 Central and peripheral nervous system [digital image]. In Anatomy and Physiology<\/em> (Section 12.1). https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/12-1-basic-structure-and-function-of-the-nervous-system<\/span><\/span><\/p>\r\nBetts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2016, May 18). Figure 13.11 The diencephalon [digital image]. In Anatomy and Physiology<\/em> (Section 13.2). https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/13-2-the-central-nervous-system<\/p>\r\nBlausen.com staff. (2014). Medical gallery of Blausen Medical 2014. WikiJournal of Medicine,<\/em> 1<\/em> (2). DOI:10.15347\/wjm\/2014.010. ISSN 2002-4436<\/span><\/p>\r\nmarkmcdermott. (2010). Split-brain patient 'Joe' being tested with stimuli presented in different visual fields. YouTube. https:\/\/www.youtube.com\/user\/markmcdermott\/search?query=split<\/p>\r\n
Mayo Clinic Staff. (n.d.). Stroke [online article]. MayoClinic.org. https:\/\/www.mayoclinic.org\/diseases-conditions\/stroke\/symptoms-causes\/syc-20350113<\/p>\r\n
Soton Brain Hub. (2016, July 29). The limbic system. YouTube. https:\/\/www.youtube.com\/watch?v=jcrWPo_s6EE&feature=youtu.be<\/p>\r\n
TED-Ed. (2013, January 31). What if we could look inside human brains? - Moran Cerf. YouTube. https:\/\/www.youtube.com\/watch?v=sewhbmh0ECg&feature=youtu.be<\/p>\r\n
TED-Ed. (2017, July 24). The left brain vs. right brain myth - Elizabeth Waters. YouTube. https:\/\/www.youtube.com\/watch?v=ZMSbDwpIyF4&feature=youtu.be<\/p>\r\n ","rendered":"
<\/p>\nFigure 8.5.1 This picture is called an <\/em>homunculus.\u00a0<\/em><\/figcaption><\/figure>\nHomunculus<\/h1>\n
The very odd-looking drawing in Figure 8.5.1 is called a homunculus. The beige mass represents a cross-sectional wedge of the human brain, and the drawing shows some areas of the brain associated with different parts of the body. As you can see, larger areas of the brain in this region are associated with the hands, face, and tongue, as compared to the areas associated with the legs and feet. Given the importance of speech, manual dexterity, and face-to-face social interactions in human beings, it is not surprising that relatively large areas of the brain are needed to control these body parts. The brain is the most complex organ in the human body and part of the central nervous system.<\/p>\n
\nWhat Is the Central Nervous System?<\/h1>\n<\/div>\n
The central nervous system<\/a> (CNS) is the part of the nervous system that includes the brain<\/a> and spinal cord<\/a>. The drawing below (Figure 8.5.2) shows the central nervous system as one of two main divisions of the total nervous system. The other main division is the peripheral nervous system<\/a> (PNS). The CNS and PNS work together to control virtually all body functions.<\/p>\nFigure 8.5.2 The two main divisions of the nervous system: the central nervous system (CNS) \u2014 which includes the brain and spinal cord \u2014 and the peripheral nervous system (PNS), which includes nerves and ganglia (singular, ganglion), which transmit information between the CNS to the rest of the body.<\/em><\/figcaption><\/figure>\nThe delicate nervous tissues of the central nervous system are protected by major physical and chemical barriers. Physically, the brain and spinal cord are surrounded by tough meninges<\/a>, a three-layer protective sheath that also contains cushioning cerebrospinal fluid<\/a>. The\u00a0bones\u00a0of the skull and spinal vertebrae also contribute to physically protecting the brain and spinal cord. Chemically, the brain and spinal cord are isolated from the circulation\u00a0\u2014\u00a0and most toxins or pathogens in the\u00a0blood\u00a0\u2014\u00a0by the\u00a0blood-brain barrier<\/a>.<\/strong>\u00a0The blood-brain barrier is a highly selective membrane formed of endothelial\u00a0cells\u00a0that separates the circulating\u00a0blood\u00a0from extracellular fluid in the CNS. The barrier allows\u00a0water, certain gases, glucose, and some other molecules needed by the brain and spinal cord to cross from the blood into the CNS, while keeping out potentially harmful substances. These physical and chemical barriers make the CNS less susceptible to injury than the PNS. However, damage to the CNS is likely to have more serious consequences.<\/p>\n\nThe Brain<\/h1>\n<\/div>\n
The\u00a0brain<\/a><\/strong> is the control center of not only the rest of the nervous system, but of the entire organism. The adult brain makes up only about 2% of the body\u2019s weight, but it uses about 20% of the body\u2019s total energy. The brain contains an estimated 100 billion neurons, and each neuron<\/a> has thousands of synaptic connections to other neurons. The brain also has about the same number of neuroglia<\/a> as neurons. No wonder the brain uses so much energy! In addition, the brain uses mostly glucose<\/a> for energy. As a result, if the brain is deprived of glucose, it can lead to unconsciousness. The brain is able to store some glucose in the form of glycogen, but in much smaller amounts than are found in the liver and skeletal muscles.<\/p>\nThe brain controls such mental processes as reasoning, imagination, memory, and language. It also interprets information from the senses and commands the body to respond appropriately. It controls basic physical processes (such as breathing and heartbeat), as well as voluntary activities (such as walking and writing). The brain has three major regions: the hindbrain, the midbrain and the forebrain. These parts are shown in Figure 8.5.3 and described below.<\/p>\nFigure 8.5.3 Diagram of the forebrain, midbrain and hindbrain. <\/em><\/figcaption><\/figure>\n\n <\/p>\n<\/div>\n
The Hindbrain<\/h2>\nFigure 8.5.4 The hindbrain consists of the cerebellum,<\/em> medulla oblongata, and the pons. It plays the extremely important role of connecting the brain to the rest of the body via the spinal cord.<\/em><\/figcaption><\/figure>\nThe\u00a0hindbrain<\/a>, <\/strong>which includes the cerebellum<\/a>, medulla oblongata<\/a>, and the pons<\/a>. The hindbrain is the lowest part of the brain. It resembles a stalk and platform on which the cerebrum is perched. The components of the hindbrain connect the rest of the brain with the spinal cord and passes nerve impulses between the brain and spinal cord.<\/p>\nCerebellum<\/h3>\n
The\u00a0cerebellum<\/a><\/strong> is located just below the cerebrum and at the back of the brain behind the brain stem. It coordinates your voluntary movements, balance, and posture.\u00a0 Information from your inner ear, joints and muscles, and eyes are all knitted together in the cerebellum so that you have awareness of where you are in 3-dimensional space.\u00a0 Patients who have suffered damage to their cerebellum may suffer from balance disorder. In addition the cerebellum plays a major role in motor learning (like how to ride a bike or how to do a backflip on a trampoline) through trial and error.\u00a0 While traditionally, the cerebellum was thought to only be involved in motor functions, we now know that it also plays an important role in memory and learning.<\/p>\nMedulla Oblongata<\/h3>\n
The\u00a0medulla oblongata<\/a><\/strong> makes up part of the brainstem and sits in front of and just below the cerebellum, at the very top of the spinal cord.\u00a0 It is responsible for control of heart rate, respiration rate and blood pressure, as well as reflexes such as vomiting, coughing, sneezing and swallowing.<\/p>\nPons<\/h3>\n
The\u00a0pons<\/a><\/strong> is located in front of the cerebellum and above the medulla oblongata.\u00a0 It has several functions, including receiving sensory information from the face, regulating rate and depth of breaths, as well as sleep cycles.<\/p>\nMidbrain<\/h2>\nFigure 8.5.5 The brainstem includes the midbrain, the pons and the medulla oblongata.<\/em><\/figcaption><\/figure>\nThe midbrain is the topmost part of the brainstem and is the essential connection between and brain and spinal cord.\u00a0 The three main parts of the midbrain are the colliculi, the tegmentum, and the cerebral peduncles.\u00a0 These structures are all considered part of the brainstem, which consists of the medulla oblongata, the pons and the midbrain.<\/p>\n
Reticular Activating System<\/h3>\n
The reticular activating system<\/a> (RAS) is responsible for the sleep-wake cycle and wakefulness.\u00a0 It also regulates attention, ability to focus and arousal.<\/p>\nForebrain<\/h2>\n
The forebrain is the anterior (forwardmost) part of the brain and includes the cerebrum, the thalamus and hypothalamus, hippocampus, amygdala, and limbic system.\u00a0 This portion of the brain is responsible for processing incoming sensory information, performing complex cognitive activities (speech, abstract thought, etc) and governing voluntary motor movements.\u00a0 \u00a0The forebrain also controls body temperature, reproductive functions, eating, sleeping and the display of emotions.<\/p>\n
Cerebrum<\/h3>\n
The\u00a0cerebrum<\/a><\/strong>\u00a0is the largest part of the brain. It controls conscious, intellectual functions.\u00a0Among other things,\u00a0it controls reasoning, language, memory, sight, touch, and hearing. When you read a book, play a video game, or recognize a classmate, you are using your cerebrum.<\/p>\nHemispheres and Lateralization of the Cerebrum<\/h4>\n
The cerebrum is divided from front to back into two halves called the left and right\u00a0hemispheres<\/a>.<\/strong>\u00a0The two hemispheres are connected by a thick bundle of axons, known as the corpus callosum<\/a>, which lies deep within the brain. The corpus callosum is the main avenue of\u00a0communication between the two hemispheres. It connects each point in the cerebrum to the mirror-image point in the opposite hemisphere.<\/p>\nThe right and left hemispheres of the cerebrum are similar in shape, and most areas of cerebrum are found in both hemispheres. Some areas, however, show\u00a0lateralization<\/a>,<\/strong>\u00a0or a\u00a0concentration\u00a0in one hemisphere or the other.\u00a0In most people, for example, language functions are more concentrated in the left hemisphere, whereas abstract reasoning and visual-spatial abilities are more concentrated in the right hemisphere.<\/p>\nFor reasons that are not yet clear, each hemisphere of the brain interacts primarily with the opposite side of the body. The left side of the brain receives messages from and sends commands to the right side of the body, and the right side of the brain\u00a0receives messages from and sends commands to the left side of the body. Sensory nerves from the spinal cord to the brain and motor nerves from the brain to the spinal cord both cross the midline of the body at the level of the brain stem.<\/p>\n
Lobes of the Cerebrum<\/h4>\n
Each hemisphere<\/a> of the cerebrum is further divided into the four lobes shown in Figure 8.5.6 and described below.<\/p>\nFigure 8.5.6 The cerebrum is organized into four lobes: frontal, parietal, occipital, and temporal.<\/em><\/figcaption><\/figure>\n\nEach hemisphere of the cerebrum consists of four parts, called lobes. Each lobe is associated with particular brain functions. Just one function of each lobe is listed here.<\/p>\n<\/div>\n
\n- The\u00a0frontal lobes<\/a><\/strong>\u00a0are located at the front of the brain behind the forehead. The frontal lobes are associated with executive functions, such as attention, self-control, planning, problem solving, reasoning, abstract thought, language, and personality.<\/li>\n
- The\u00a0parietal lobes<\/a><\/strong>\u00a0are located behind the frontal lobes at the top of the head. The parietal lobes are involved in sensation \u2014 including\u00a0temperature, touch, and taste. Reading and arithmetic are also functions of the parietal lobes.<\/li>\n
- The\u00a0temporal lobes<\/a><\/strong>\u00a0are located at the sides of the head below the frontal and parietal lobes. The temporal lobes enable hearing, the formation and retrieval of memories, and the integration of memories and sensations.<\/li>\n
- The\u00a0occipital lobes<\/a><\/strong>\u00a0are located at the back of the head below the parietal lobes. The occipital lobes are the smallest of the four pairs of lobes. They are dedicated almost solely to\u00a0vision.<\/li>\n<\/ul>\n
Cerebral Cortex<\/h4>\n
Most of the information processing in the brain actually takes place in the\u00a0cerebral cortex<\/a><\/strong>, a rind of gray matter and other tissues just a few millimetres thick that makes up the outer surface of the cerebrum in both hemispheres of the brain. The cerebral cortex has many folds in it, greatly increasing the amount of surface area of the brain that can fit within the skull. Because of all the folds in the human cerebral cortex, it has a surface area of about 2,500 cm2<\/sup>\u00a0(2.5 ft2<\/sup>). The size and importance of the cerebral cortex is far greater in the human brain than the brains of any other vertebrates, including nonhuman\u00a0primates.<\/p>\nThe Limbic System<\/h3>\n
The limbic system consists of the hypothalamus, thalamus, the hippocampus and amygdala. The structures and interacting areas of the\u00a0limbic system<\/a><\/b>\u00a0are involved in motivation, emotion, learning, and memory.<\/p>\nThalamus and Hypothalamus<\/h4>\n
Several structures are located deep within the brain and are important for communication between the brain and spinal cord (or the rest of the body). These structures include the hypothalamus and thalamus. The diagram below (Figure 8.5.7) shows where these structures are located in the brain. Like the two halves of the cerebrum, the hypothalamus and thalamus exist in two halves, one in each hemisphere.<\/p>\nFigure 8.5.7 Structures deep within the brain include the hypothalamus and thalamus.<\/em><\/figcaption><\/figure>\nThe\u00a0hypothalamus<\/a><\/strong>\u00a0is located just above the brain stem, and is about the size of an almond. The hypothalamus is responsible for certain metabolic processes and other activities of the autonomic nervous system<\/a>, including body\u00a0temperature,\u00a0heart\u00a0rate, hunger, thirst, fatigue, sleep, wakefulness, and circadian (24-hour) rhythms. The hypothalamus is also an important emotional center of the brain. The hypothalamus can regulate so many body functions because it responds to many different internal and external signals, including messages from the brain, light, steroid hormones, stress, and invading pathogens, among others.<\/p>\nOne way the hypothalamus influences body functions is by synthesizing hormones that directly influence body processes. It synthesizes the hormone oxytocin<\/a>, which stimulates uterine contractions during childbirth and the letdown of milk during lactation. It also synthesizes antidiuretic hormone<\/a>, which stimulates the kidneys to reabsorb more water and excrete more concentrated urine. These two hormones are sent from the hypothalamus via a stalk-like structure called the infundibulum (see Figure 8.5.7) directly to the posterior (back) portion of the pituitary gland, which secretes them into the blood.<\/p>\nThe main way the hypothalamus influences body functions is by controlling the\u00a0pituitary gland<\/a>, known as the master gland of the\u00a0endocrine system. The hypothalamus synthesizes neurohormones called releasing factors that travel through the infundibulum directly to the anterior (front) part of the pituitary gland. The releasing factors generally either stimulate or inhibit the secretion of anterior pituitary hormones, most of which control other glands of the endocrine system.<\/p>\n
Medulla Oblongata<\/h3>\r\nThe\u00a0[pb_glossary id=\"3075\"]medulla oblongata[\/pb_glossary]<\/strong> makes up part of the brainstem and sits in front of and just below the cerebellum, at the very top of the spinal cord.\u00a0 It is responsible for control of heart rate, respiration rate and blood pressure, as well as reflexes such as vomiting, coughing, sneezing and swallowing.\r\nPons<\/h3>\r\nThe\u00a0[pb_glossary id=\"3076\"]pons[\/pb_glossary]<\/strong> is located in front of the cerebellum and above the medulla oblongata.\u00a0 It has several functions, including receiving sensory information from the face, regulating rate and depth of breaths, as well as sleep cycles.\r\nMidbrain<\/h2>\r\n[caption id=\"attachment_3079\" align=\"alignleft\" width=\"317\"] Figure 8.5.5 The brainstem includes the midbrain, the pons and the medulla oblongata.<\/em>[\/caption]\r\n\r\nThe midbrain is the topmost part of the brainstem and is the essential connection between and brain and spinal cord.\u00a0 The three main parts of the midbrain are the colliculi, the tegmentum, and the cerebral peduncles.\u00a0 These structures are all considered part of the brainstem, which consists of the medulla oblongata, the pons and the midbrain.\r\nReticular Activating System<\/h3>\r\nThe [pb_glossary id=\"3082\"]reticular activating system[\/pb_glossary] (RAS) is responsible for the sleep-wake cycle and wakefulness.\u00a0 It also regulates attention, ability to focus and arousal.\r\nForebrain<\/h2>\r\nThe forebrain is the anterior (forwardmost) part of the brain and includes the cerebrum, the thalamus and hypothalamus, hippocampus, amygdala, and limbic system.\u00a0 This portion of the brain is responsible for processing incoming sensory information, performing complex cognitive activities (speech, abstract thought, etc) and governing voluntary motor movements.\u00a0 \u00a0The forebrain also controls body temperature, reproductive functions, eating, sleeping and the display of emotions.\r\nCerebrum<\/h3>\r\nThe\u00a0[pb_glossary id=\"5941\"]cerebrum[\/pb_glossary]<\/strong>\u00a0is the largest part of the brain. It controls conscious, intellectual functions.\u00a0Among other things,\u00a0it controls reasoning, language, memory, sight, touch, and hearing. When you read a book, play a video game, or recognize a classmate, you are using your cerebrum.\r\nHemispheres and Lateralization of the Cerebrum<\/h4>\r\nThe cerebrum is divided from front to back into two halves called the left and right\u00a0[pb_glossary id=\"3083\"]hemispheres[\/pb_glossary].<\/strong>\u00a0The two hemispheres are connected by a thick bundle of axons, known as the [pb_glossary id=\"5955\"]corpus callosum[\/pb_glossary], which lies deep within the brain. The corpus callosum is the main avenue of\u00a0communication between the two hemispheres. It connects each point in the cerebrum to the mirror-image point in the opposite hemisphere.\r\n\r\nThe right and left hemispheres of the cerebrum are similar in shape, and most areas of cerebrum are found in both hemispheres. Some areas, however, show\u00a0[pb_glossary id=\"3085\"]lateralization[\/pb_glossary],<\/strong>\u00a0or a\u00a0concentration\u00a0in one hemisphere or the other.\u00a0In most people, for example, language functions are more concentrated in the left hemisphere, whereas abstract reasoning and visual-spatial abilities are more concentrated in the right hemisphere.\r\n\r\nFor reasons that are not yet clear, each hemisphere of the brain interacts primarily with the opposite side of the body. The left side of the brain receives messages from and sends commands to the right side of the body, and the right side of the brain\u00a0receives messages from and sends commands to the left side of the body. Sensory nerves from the spinal cord to the brain and motor nerves from the brain to the spinal cord both cross the midline of the body at the level of the brain stem.\r\nLobes of the Cerebrum<\/h4>\r\nEach [pb_glossary id=\"3083\"]hemisphere[\/pb_glossary] of the cerebrum is further divided into the four lobes shown in Figure 8.5.6 and described below.\r\n\r\n[caption id=\"attachment_3086\" align=\"aligncenter\" width=\"680\"] Figure 8.5.6 The cerebrum is organized into four lobes: frontal, parietal, occipital, and temporal.<\/em>[\/caption]\r\n\r\n\r\n\r\nEach hemisphere of the cerebrum consists of four parts, called lobes. Each lobe is associated with particular brain functions. Just one function of each lobe is listed here.\r\n\r\n<\/div>\r\n\r\n \t- The\u00a0[pb_glossary id=\"6021\"]frontal lobes[\/pb_glossary]<\/strong>\u00a0are located at the front of the brain behind the forehead. The frontal lobes are associated with executive functions, such as attention, self-control, planning, problem solving, reasoning, abstract thought, language, and personality.<\/li>\r\n \t
- The\u00a0[pb_glossary id=\"3088\"]parietal lobes[\/pb_glossary]<\/strong>\u00a0are located behind the frontal lobes at the top of the head. The parietal lobes are involved in sensation \u2014 including\u00a0temperature, touch, and taste. Reading and arithmetic are also functions of the parietal lobes.<\/li>\r\n \t
- The\u00a0[pb_glossary id=\"3089\"]temporal lobes[\/pb_glossary]<\/strong>\u00a0are located at the sides of the head below the frontal and parietal lobes. The temporal lobes enable hearing, the formation and retrieval of memories, and the integration of memories and sensations.<\/li>\r\n \t
- The\u00a0[pb_glossary id=\"3090\"]occipital lobes[\/pb_glossary]<\/strong>\u00a0are located at the back of the head below the parietal lobes. The occipital lobes are the smallest of the four pairs of lobes. They are dedicated almost solely to\u00a0vision.<\/li>\r\n<\/ul>\r\n
Cerebral Cortex<\/h4>\r\nMost of the information processing in the brain actually takes place in the\u00a0[pb_glossary id=\"5937\"]cerebral cortex[\/pb_glossary]<\/strong>, a rind of gray matter and other tissues just a few millimetres thick that makes up the outer surface of the cerebrum in both hemispheres of the brain. The cerebral cortex has many folds in it, greatly increasing the amount of surface area of the brain that can fit within the skull. Because of all the folds in the human cerebral cortex, it has a surface area of about 2,500 cm2<\/sup>\u00a0(2.5 ft2<\/sup>). The size and importance of the cerebral cortex is far greater in the human brain than the brains of any other vertebrates, including nonhuman\u00a0primates.\r\nThe Limbic System<\/h3>\r\nThe limbic system consists of the hypothalamus, thalamus, the hippocampus and amygdala. The structures and interacting areas of the\u00a0[pb_glossary id=\"3098\"]limbic system[\/pb_glossary]<\/b>\u00a0are involved in motivation, emotion, learning, and memory.\r\nThalamus and Hypothalamus<\/h4>\r\nSeveral structures are located deep within the brain and are important for communication between the brain and spinal cord (or the rest of the body). These structures include the hypothalamus and thalamus. The diagram below (Figure 8.5.7) shows where these structures are located in the brain. Like the two halves of the cerebrum, the hypothalamus and thalamus exist in two halves, one in each hemisphere.\r\n\r\n[caption id=\"attachment_3092\" align=\"alignleft\" width=\"363\"] Figure 8.5.7 Structures deep within the brain include the hypothalamus and thalamus.<\/em>[\/caption]\r\n\r\nThe\u00a0[pb_glossary id=\"2937\"]hypothalamus[\/pb_glossary]<\/strong>\u00a0is located just above the brain stem, and is about the size of an almond. The hypothalamus is responsible for certain metabolic processes and other activities of the [pb_glossary id=\"5899\"]autonomic nervous system[\/pb_glossary], including body\u00a0temperature,\u00a0heart\u00a0rate, hunger, thirst, fatigue, sleep, wakefulness, and circadian (24-hour) rhythms. The hypothalamus is also an important emotional center of the brain. The hypothalamus can regulate so many body functions because it responds to many different internal and external signals, including messages from the brain, light, steroid hormones, stress, and invading pathogens, among others.\r\n\r\nOne way the hypothalamus influences body functions is by synthesizing hormones that directly influence body processes. It synthesizes the hormone [pb_glossary id=\"3093\"]oxytocin[\/pb_glossary], which stimulates uterine contractions during childbirth and the letdown of milk during lactation. It also synthesizes [pb_glossary id=\"5893\"]antidiuretic hormone[\/pb_glossary], which stimulates the kidneys to reabsorb more water and excrete more concentrated urine. These two hormones are sent from the hypothalamus via a stalk-like structure called the infundibulum (see Figure 8.5.7) directly to the posterior (back) portion of the pituitary gland, which secretes them into the blood.\r\n\r\nThe main way the hypothalamus influences body functions is by controlling the\u00a0[pb_glossary id=\"2938\"]pituitary gland[\/pb_glossary], known as the master gland of the\u00a0endocrine system. The hypothalamus synthesizes neurohormones called releasing factors that travel through the infundibulum directly to the anterior (front) part of the pituitary gland. The releasing factors generally either stimulate or inhibit the secretion of anterior pituitary hormones, most of which control other glands of the endocrine system.\r\n\r\nThe\u00a0[pb_glossary id=\"3095\"]thalamus[\/pb_glossary],<\/strong> which is located near the hypothalamus (see Figure 8.5.7), is a major hub for information traveling back and forth between the spinal cord and cerebrum. It relays sensory signals to the cerebral cortex and motor signals to the spinal cord. It is also involved in the regulation of consciousness, sleep, and alertness.\r\n\r\nHippocampus and Amygdala<\/h4>\r\nThe [pb_glossary id=\"3096\"]hippocampus[\/pb_glossary] is a complex structure embedded deep in the temporal lobe.\u00a0 It plays a major role in learning and memory and contributes to regulation of motivation and emotion. The amygdala is the part of the brain responsible for formation and storage of memories associated with emotional events.\r\n\r\nWatch \"The Limbic System\" by Soton Brain Hub to learn about the location and functions of the limbic system.\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=jcrWPo_s6EE\r\n
The Limbic System, Soton Brain Hub, 2016.<\/p>\r\n\r\n
Spinal Cord<\/h1>\r\n<\/div>\r\nThe\u00a0[pb_glossary id=\"3010\"]spinal cord[\/pb_glossary]<\/strong> is a long, thin, tubular bundle of nervous tissues that extends from the brain stem and continues down the center of the back to the pelvis. It is highlighted in yellow in Figure 8.5.8. The spinal cord is enclosed within, but is shorter than, the vertebral column.\r\n\r\n[caption id=\"attachment_3099\" align=\"alignnone\" width=\"482\"] Figure 8.5.8 The spinal cord (yellow) runs from the bottom of the brain to the lower back.<\/em>[\/caption]\r\nStructure of the Spinal Cord<\/h2>\r\nThe center of the spinal cord consists of gray matter, which is made up mainly of cell bodies of neurons, including interneurons and motor neurons. The gray matter is surrounded by white matter that consists mainly of myelinated axons of motor and sensory neurons. Spinal nerves, which connect the spinal cord to the PNS, exit from the spinal cord between vertebrae (see Figure 8.5.9).\r\n\r\n \r\n\r\n\r\n[caption id=\"attachment_3100\" align=\"alignleft\" width=\"291\"] Figure 8.5.9 This model shows three vertebrae (white) with branching spinal nerves (yellow) emerging from the either side of the spinal cord between vertebrae.<\/em>[\/caption]\r\n\r\n<\/div>\r\nFunctions of the Spinal Cord<\/h2>\r\nThe spinal cord serves as an information superhighway. It passes messages from the body to the brain and from the brain to the body. Sensory (afferent) nerves carry\u00a0nerve impulses\u00a0to the brain from sensory receptor\u00a0cells\u00a0everywhere in and on the body. Motor (efferent) nerves carry nerve impulses away from the brain to glands, organs, or\u00a0muscles throughout the body.\r\n\r\nThe spinal cord also independently controls certain rapid responses called\u00a0reflexes<\/strong> without any input from the brain. You can see how this may happen in Figure 8.5.10. A sensory receptor responds to a sensation and sends a nerve impulse along a sensory nerve to the spinal cord. In the spinal cord, the message passes to an interneuron and from the interneuron to a motor nerve, which carries the impulse to a muscle. The muscle contracts in response. These neuron connections form a reflex arc, which requires no input from the brain. No doubt you have experienced such reflex actions yourself. For example, you may have reached out to touch a pot on the stove, not realizing that it was very hot. Virtually at the same moment that you feel the burning heat, you jerk your arm back and remove your hand from the pot.\r\n\r\n \r\n\r\n\r\n[caption id=\"attachment_3101\" align=\"alignnone\" width=\"1038\"] Figure 8.5.10 This diagram shows what happens in a long reflex (top), in which sensory nerves carry the message all the way to the spinal cord; and in a short reflex (bottom), in which sensory nerves travel only to a ganglion outside the spinal cord. Note that interneurons are involved in reflexes, connecting sensory and motor neurons, but they are not actually shown in the diagram.<\/em>[\/caption]\r\n\r\n<\/div>\r\nInjuries to the Spinal Cord<\/h2>\r\nPhysical damage to the spinal cord may result in\u00a0[pb_glossary id=\"3102\"]paralysis[\/pb_glossary],<\/strong> which is loss of sensation and movement in part of the body. Paralysis generally affects all the areas of the body below the level of the injury, because nerve impulses are interrupted and can no longer travel back and forth between the brain and body beyond that point. If an injury to the spinal cord produces nothing more than swelling, the symptoms may be transient. However, if nerve fibres (axons) in the spinal cord are badly damaged, the loss of function may be permanent. Experimental studies have shown that spinal nerve fibres attempt to regrow, but tissue destruction usually produces scar tissue that cannot be penetrated by the regrowing nerves, as well other factors that inhibit nerve fibre regrowth in the central nervous system.\r\n\r\nFeature: My\u00a0Human Body<\/h1>\r\n<\/div>\r\nEach year, many millions of people have a stroke<\/a>, and stroke is the second leading cause of death in adults.\u00a0[pb_glossary id=\"3103\"]Stroke[\/pb_glossary],<\/strong>\u00a0also known as cerebrovascular accident, occurs when poor blood flow to the brain results in the death of brain cells. There are two main types of strokes:\r\n\r\n \t- Ischemic strokes occur due to lack of blood flow because of a blood clot in an artery going to the brain.<\/li>\r\n \t
- Hemorrhagic strokes occur due to bleeding from a broken blood vessel in the brain.<\/li>\r\n<\/ul>\r\nEither type of stroke may result in paralysis, loss of the ability to speak or comprehend speech, loss of bladder control, personality changes, and many other potential effects, depending on the part of the brain that is injured. The effects of a stroke may be mild and transient or more severe and permanent. A stroke may even be fatal. It generally depends on the type of stroke and how extensive it is.\r\n\r\nAre you at risk of a stroke? The main risk factor for stroke is age \u2014 about two-thirds of strokes occur in people over the age of 65. There is nothing you can do about your age, but most other stroke risk factors can be reduced with lifestyle changes or medications. The risk factors include high blood pressure, tobacco smoking, obesity, high blood cholesterol, diabetes mellitus, and atrial fibrillation.\r\n\r\nChances are good that you or someone you know is at risk of a stroke, so it is important to recognize a stroke if one occurs. A stroke is a medical emergency, and the more quickly treatment is given, the better the outcome is likely to be. In the case of ischemic strokes, the use of clot-busting drugs may prevent permanent brain damage if administered within three or four hours of the stroke. Remembering the signs of a stroke is easy. They are summed up by the acronym FAST.\r\n\r\n
\r\n8.5 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- The [pb_glossary id=\"5933\"]central nervous system[\/pb_glossary] is the part of the nervous system that includes the [pb_glossary id=\"5915\"]brain[\/pb_glossary] and [pb_glossary id=\"3010\"]spinal cord[\/pb_glossary]. It is physically protected by\u00a0bones, meninges, and [pb_glossary id=\"5939\"]cerebrospinal fluid[\/pb_glossary]. It is chemically protected by the blood-brain barrier.<\/li>\r\n \t
- The brain is the control center of the nervous system and of the entire organism. The brain uses a relatively large proportion of the body\u2019s\u00a0energy, primarily in the form of glucose.<\/li>\r\n \t
- The brain is divided into three major parts, each with different functions: the hindbrain, the midbrain and the forebrain.<\/li>\r\n \t
- Hindbrain consists of the medulla oblongata, the pons and the cerebellum, each of which perform specific functions.<\/li>\r\n \t
- The midbrain is primarily responsible for motor movement and in auditory and visual processing.<\/li>\r\n \t
- The forebrain contains many structures including:\r\n
\r\n \t- The cerebrum, which is further divided into left and right hemispheres. Each hemisphere has four lobes: frontal, parietal, temporal, and occipital. Each lobe is associated with specific senses or other functions.<\/li>\r\n \t
- The cerebrum\u00a0has a\u00a0thin outer layer called the cerebral cortex. Its many folds give it a large surface area. This is where most information processing takes place.<\/li>\r\n \t
- Inner structures of the brain include the hypothalamus \u2014 which controls the\u00a0endocrine system\u00a0via the\u00a0pituitary gland\u00a0\u2014 and the thalamus, which has several involuntary functions.<\/li>\r\n \t
- The hippocampus and amygdala, which are part of the limbic system and play important roles in memory, learning and emotions.<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t
- The spinal cord is a tubular bundle of nervous tissues that extends from the head down the middle of the back to the pelvis. It functions mainly to connect the brain with the\u00a0peripheral nervous system. It also controls certain rapid responses called reflexes without any input from the brain.<\/li>\r\n \t
- A spinal cord injury may lead to paralysis (loss of sensation and movement) of the body below the level of the injury, because nerve impulses can no longer travel up and down the spinal cord beyond that point.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n8.5 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- What is the central nervous system?<\/li>\r\n \t
- How is the central nervous system protected?<\/li>\r\n \t
- What is the overall function of the brain?<\/li>\r\n \t
- Identify the three main parts of the brain and one function of each part.<\/li>\r\n \t
- Describe the hemispheres of the brain.<\/li>\r\n \t
- Explain and give examples of lateralization of the brain.<\/li>\r\n \t
- Identify one function of each of the four lobes of the cerebrum.<\/li>\r\n \t
- [h5p id=\"562\"]<\/li>\r\n \t
- [h5p id=\"563\"]<\/li>\r\n \t
- Summarize the structure and function of the cerebral cortex. Explain how the hypothalamus controls the endocrine system.<\/li>\r\n \t
- Describe the spinal cord.<\/li>\r\n \t
- What is the main function of the spinal cord?<\/li>\r\n \t
- Explain how reflex actions occur.<\/li>\r\n \t
- Why do severe spinal cord injuries usually cause paralysis?<\/li>\r\n \t
- What do you think are some possible consequences of severe damage to the brain stem? How might this compare to the consequences of severe damage to the frontal lobe? Explain your answer.<\/li>\r\n \t
- Information travels very quickly in the nervous system, but generally, the longer the path between areas, the longer it takes. Based on this, explain why you think reflexes often occur at the spinal cord level, and do not require input from the brain.<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
\r\n8.5 Explore More<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=sewhbmh0ECg\r\nWhat if we could look inside human brains? - Moran Cerf, TED-Ed, 2013.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=ZMSbDwpIyF4\r\n
The left brain vs. right brain myth - Elizabeth Waters, TED-Ed, 2017.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?time_continue=1&v=aCv4K5aStdU&feature=emb_logo\r\n
Split-brain patient 'Joe' being tested with stimuli presented in different visual fields,\r\nmarkmcdermott, 2010.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n
Attributes<\/h2>\r\nFigure 8.5.1<\/strong>\r\n\r\nSensory_Homunculus-en.svg<\/a> by Popadius<\/a> on Wikimedia Commons is used under a CC BY 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0\/deed.en) license. (This is a derivative work from File:1421 Sensory Homunculus<\/a>.jpg by OpenStax College<\/a>)\r\n\r\nFigure 8.5.2<\/strong>\r\n\r\nOverview_of_Nervous_System<\/a>\u00a0by OpenStax<\/a> on Wikimedia Commons is used under a CC BY 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en) license.\r\n\r\nFigure 8.5.3<\/strong>\r\n\r\nDiagram_showing_the_brain_stem_which_includes_the_medulla_oblongata,_the_pons_and_the_midbrain_(2)_CRUK_294.svg<\/a> by Cancer Research UK<\/a> on Wikimedia Commons is used under a CC BY-SA 4.0 <\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\nFigure 8.5.4<\/strong>\r\n\r\nBrain_bulbar_region.svg<\/a> by Fvasconcellos<\/a> on Wikimedia Commons is used under a CC BY 2.5<\/a> license (derivative work from Brain human sagittal section.svg<\/a>\u00a0 by Patrick J. Lynch; Brain bulbar region.PNG<\/a> by DO11.10<\/a>).\r\n\r\nFigure 8.5.5<\/strong>\r\n\r\nMidbrain<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY 3.0 <\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0) license.\r\n\r\nFigure 8.5.6<\/strong>\r\n\r\nBrainLobes<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY 3.0 <\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0) license.\u00a0<\/span>\r\n\r\nFigure 8.5.7<\/strong>\r\n\r\nDiencephalon<\/a> by OpenStax<\/a> Wikimedia Commons is used under a CC BY 4.0 <\/a>(https:\/\/creativecommons.org\/licenses\/by\/4.0) license.\r\n\r\nFigure 8.5.8<\/strong>\r\n\r\nSpinalCord<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY 3.0 <\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0) license.\u00a0<\/span>\r\n\r\nFigure 8.5.9<\/strong>\r\n\r\nSpinal_readjustment_3<\/a> by Tomwsulcer<\/a> on\u00a0 Wikimedia Commons is used under a CC0 1.0<\/a> Universal Public Domain Dedication license (https:\/\/creativecommons.org\/publicdomain\/zero\/1.0\/deed.en).\r\n\r\nFigure 8.5.10<\/strong>\r\n\r\n1507_Short_and_Long_Reflexes<\/a> by OpenStax<\/a> on Wikimedia Commons is used under a CC BY 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en) license.\r\nReferences<\/h2>\r\n
Betts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2013, 28 May). Figure 14.23<\/span>\u00a0<\/span>The sensory homunculus <\/span>[digital image]. In Anatomy and Physiology<\/em> (Section 14.2). OpenStax. https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/14-2-central-processing\r\n<\/span><\/span><\/p>\r\nBetts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2013, 28 May). Figure 15.8 Short and long reflexes [digital image]. In Anatomy and Physiology<\/em> (Section 15.2). OpenStax. https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/15-2-autonomic-reflexes-and-homeostasis<\/p>\r\nBetts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2016, May 18). <\/span><\/span>Figure 12.2 Central and peripheral nervous system [digital image]. In Anatomy and Physiology<\/em> (Section 12.1). https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/12-1-basic-structure-and-function-of-the-nervous-system<\/span><\/span><\/p>\r\nBetts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2016, May 18). Figure 13.11 The diencephalon [digital image]. In Anatomy and Physiology<\/em> (Section 13.2). https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/13-2-the-central-nervous-system<\/p>\r\nBlausen.com staff. (2014). Medical gallery of Blausen Medical 2014. WikiJournal of Medicine,<\/em> 1<\/em> (2). DOI:10.15347\/wjm\/2014.010. ISSN 2002-4436<\/span><\/p>\r\nmarkmcdermott. (2010). Split-brain patient 'Joe' being tested with stimuli presented in different visual fields. YouTube. https:\/\/www.youtube.com\/user\/markmcdermott\/search?query=split<\/p>\r\n
Mayo Clinic Staff. (n.d.). Stroke [online article]. MayoClinic.org. https:\/\/www.mayoclinic.org\/diseases-conditions\/stroke\/symptoms-causes\/syc-20350113<\/p>\r\n
Soton Brain Hub. (2016, July 29). The limbic system. YouTube. https:\/\/www.youtube.com\/watch?v=jcrWPo_s6EE&feature=youtu.be<\/p>\r\n
TED-Ed. (2013, January 31). What if we could look inside human brains? - Moran Cerf. YouTube. https:\/\/www.youtube.com\/watch?v=sewhbmh0ECg&feature=youtu.be<\/p>\r\n
TED-Ed. (2017, July 24). The left brain vs. right brain myth - Elizabeth Waters. YouTube. https:\/\/www.youtube.com\/watch?v=ZMSbDwpIyF4&feature=youtu.be<\/p>\r\n ","rendered":"
<\/p>\nFigure 8.5.1 This picture is called an <\/em>homunculus.\u00a0<\/em><\/figcaption><\/figure>\nHomunculus<\/h1>\n
The very odd-looking drawing in Figure 8.5.1 is called a homunculus. The beige mass represents a cross-sectional wedge of the human brain, and the drawing shows some areas of the brain associated with different parts of the body. As you can see, larger areas of the brain in this region are associated with the hands, face, and tongue, as compared to the areas associated with the legs and feet. Given the importance of speech, manual dexterity, and face-to-face social interactions in human beings, it is not surprising that relatively large areas of the brain are needed to control these body parts. The brain is the most complex organ in the human body and part of the central nervous system.<\/p>\n
\nWhat Is the Central Nervous System?<\/h1>\n<\/div>\n
The central nervous system<\/a> (CNS) is the part of the nervous system that includes the brain<\/a> and spinal cord<\/a>. The drawing below (Figure 8.5.2) shows the central nervous system as one of two main divisions of the total nervous system. The other main division is the peripheral nervous system<\/a> (PNS). The CNS and PNS work together to control virtually all body functions.<\/p>\nFigure 8.5.2 The two main divisions of the nervous system: the central nervous system (CNS) \u2014 which includes the brain and spinal cord \u2014 and the peripheral nervous system (PNS), which includes nerves and ganglia (singular, ganglion), which transmit information between the CNS to the rest of the body.<\/em><\/figcaption><\/figure>\nThe delicate nervous tissues of the central nervous system are protected by major physical and chemical barriers. Physically, the brain and spinal cord are surrounded by tough meninges<\/a>, a three-layer protective sheath that also contains cushioning cerebrospinal fluid<\/a>. The\u00a0bones\u00a0of the skull and spinal vertebrae also contribute to physically protecting the brain and spinal cord. Chemically, the brain and spinal cord are isolated from the circulation\u00a0\u2014\u00a0and most toxins or pathogens in the\u00a0blood\u00a0\u2014\u00a0by the\u00a0blood-brain barrier<\/a>.<\/strong>\u00a0The blood-brain barrier is a highly selective membrane formed of endothelial\u00a0cells\u00a0that separates the circulating\u00a0blood\u00a0from extracellular fluid in the CNS. The barrier allows\u00a0water, certain gases, glucose, and some other molecules needed by the brain and spinal cord to cross from the blood into the CNS, while keeping out potentially harmful substances. These physical and chemical barriers make the CNS less susceptible to injury than the PNS. However, damage to the CNS is likely to have more serious consequences.<\/p>\n\nThe Brain<\/h1>\n<\/div>\n
The\u00a0brain<\/a><\/strong> is the control center of not only the rest of the nervous system, but of the entire organism. The adult brain makes up only about 2% of the body\u2019s weight, but it uses about 20% of the body\u2019s total energy. The brain contains an estimated 100 billion neurons, and each neuron<\/a> has thousands of synaptic connections to other neurons. The brain also has about the same number of neuroglia<\/a> as neurons. No wonder the brain uses so much energy! In addition, the brain uses mostly glucose<\/a> for energy. As a result, if the brain is deprived of glucose, it can lead to unconsciousness. The brain is able to store some glucose in the form of glycogen, but in much smaller amounts than are found in the liver and skeletal muscles.<\/p>\nThe brain controls such mental processes as reasoning, imagination, memory, and language. It also interprets information from the senses and commands the body to respond appropriately. It controls basic physical processes (such as breathing and heartbeat), as well as voluntary activities (such as walking and writing). The brain has three major regions: the hindbrain, the midbrain and the forebrain. These parts are shown in Figure 8.5.3 and described below.<\/p>\nFigure 8.5.3 Diagram of the forebrain, midbrain and hindbrain. <\/em><\/figcaption><\/figure>\n\n <\/p>\n<\/div>\n
The Hindbrain<\/h2>\nFigure 8.5.4 The hindbrain consists of the cerebellum,<\/em> medulla oblongata, and the pons. It plays the extremely important role of connecting the brain to the rest of the body via the spinal cord.<\/em><\/figcaption><\/figure>\nThe\u00a0hindbrain<\/a>, <\/strong>which includes the cerebellum<\/a>, medulla oblongata<\/a>, and the pons<\/a>. The hindbrain is the lowest part of the brain. It resembles a stalk and platform on which the cerebrum is perched. The components of the hindbrain connect the rest of the brain with the spinal cord and passes nerve impulses between the brain and spinal cord.<\/p>\nCerebellum<\/h3>\n
The\u00a0cerebellum<\/a><\/strong> is located just below the cerebrum and at the back of the brain behind the brain stem. It coordinates your voluntary movements, balance, and posture.\u00a0 Information from your inner ear, joints and muscles, and eyes are all knitted together in the cerebellum so that you have awareness of where you are in 3-dimensional space.\u00a0 Patients who have suffered damage to their cerebellum may suffer from balance disorder. In addition the cerebellum plays a major role in motor learning (like how to ride a bike or how to do a backflip on a trampoline) through trial and error.\u00a0 While traditionally, the cerebellum was thought to only be involved in motor functions, we now know that it also plays an important role in memory and learning.<\/p>\nMedulla Oblongata<\/h3>\n
The\u00a0medulla oblongata<\/a><\/strong> makes up part of the brainstem and sits in front of and just below the cerebellum, at the very top of the spinal cord.\u00a0 It is responsible for control of heart rate, respiration rate and blood pressure, as well as reflexes such as vomiting, coughing, sneezing and swallowing.<\/p>\nPons<\/h3>\n
The\u00a0pons<\/a><\/strong> is located in front of the cerebellum and above the medulla oblongata.\u00a0 It has several functions, including receiving sensory information from the face, regulating rate and depth of breaths, as well as sleep cycles.<\/p>\nMidbrain<\/h2>\nFigure 8.5.5 The brainstem includes the midbrain, the pons and the medulla oblongata.<\/em><\/figcaption><\/figure>\nThe midbrain is the topmost part of the brainstem and is the essential connection between and brain and spinal cord.\u00a0 The three main parts of the midbrain are the colliculi, the tegmentum, and the cerebral peduncles.\u00a0 These structures are all considered part of the brainstem, which consists of the medulla oblongata, the pons and the midbrain.<\/p>\n
Reticular Activating System<\/h3>\n
The reticular activating system<\/a> (RAS) is responsible for the sleep-wake cycle and wakefulness.\u00a0 It also regulates attention, ability to focus and arousal.<\/p>\nForebrain<\/h2>\n
The forebrain is the anterior (forwardmost) part of the brain and includes the cerebrum, the thalamus and hypothalamus, hippocampus, amygdala, and limbic system.\u00a0 This portion of the brain is responsible for processing incoming sensory information, performing complex cognitive activities (speech, abstract thought, etc) and governing voluntary motor movements.\u00a0 \u00a0The forebrain also controls body temperature, reproductive functions, eating, sleeping and the display of emotions.<\/p>\n
Cerebrum<\/h3>\n
The\u00a0cerebrum<\/a><\/strong>\u00a0is the largest part of the brain. It controls conscious, intellectual functions.\u00a0Among other things,\u00a0it controls reasoning, language, memory, sight, touch, and hearing. When you read a book, play a video game, or recognize a classmate, you are using your cerebrum.<\/p>\nHemispheres and Lateralization of the Cerebrum<\/h4>\n
The cerebrum is divided from front to back into two halves called the left and right\u00a0hemispheres<\/a>.<\/strong>\u00a0The two hemispheres are connected by a thick bundle of axons, known as the corpus callosum<\/a>, which lies deep within the brain. The corpus callosum is the main avenue of\u00a0communication between the two hemispheres. It connects each point in the cerebrum to the mirror-image point in the opposite hemisphere.<\/p>\nThe right and left hemispheres of the cerebrum are similar in shape, and most areas of cerebrum are found in both hemispheres. Some areas, however, show\u00a0lateralization<\/a>,<\/strong>\u00a0or a\u00a0concentration\u00a0in one hemisphere or the other.\u00a0In most people, for example, language functions are more concentrated in the left hemisphere, whereas abstract reasoning and visual-spatial abilities are more concentrated in the right hemisphere.<\/p>\nFor reasons that are not yet clear, each hemisphere of the brain interacts primarily with the opposite side of the body. The left side of the brain receives messages from and sends commands to the right side of the body, and the right side of the brain\u00a0receives messages from and sends commands to the left side of the body. Sensory nerves from the spinal cord to the brain and motor nerves from the brain to the spinal cord both cross the midline of the body at the level of the brain stem.<\/p>\n
Lobes of the Cerebrum<\/h4>\n
Each hemisphere<\/a> of the cerebrum is further divided into the four lobes shown in Figure 8.5.6 and described below.<\/p>\nFigure 8.5.6 The cerebrum is organized into four lobes: frontal, parietal, occipital, and temporal.<\/em><\/figcaption><\/figure>\n\nEach hemisphere of the cerebrum consists of four parts, called lobes. Each lobe is associated with particular brain functions. Just one function of each lobe is listed here.<\/p>\n<\/div>\n
\n- The\u00a0frontal lobes<\/a><\/strong>\u00a0are located at the front of the brain behind the forehead. The frontal lobes are associated with executive functions, such as attention, self-control, planning, problem solving, reasoning, abstract thought, language, and personality.<\/li>\n
- The\u00a0parietal lobes<\/a><\/strong>\u00a0are located behind the frontal lobes at the top of the head. The parietal lobes are involved in sensation \u2014 including\u00a0temperature, touch, and taste. Reading and arithmetic are also functions of the parietal lobes.<\/li>\n
- The\u00a0temporal lobes<\/a><\/strong>\u00a0are located at the sides of the head below the frontal and parietal lobes. The temporal lobes enable hearing, the formation and retrieval of memories, and the integration of memories and sensations.<\/li>\n
- The\u00a0occipital lobes<\/a><\/strong>\u00a0are located at the back of the head below the parietal lobes. The occipital lobes are the smallest of the four pairs of lobes. They are dedicated almost solely to\u00a0vision.<\/li>\n<\/ul>\n
Cerebral Cortex<\/h4>\n
Most of the information processing in the brain actually takes place in the\u00a0cerebral cortex<\/a><\/strong>, a rind of gray matter and other tissues just a few millimetres thick that makes up the outer surface of the cerebrum in both hemispheres of the brain. The cerebral cortex has many folds in it, greatly increasing the amount of surface area of the brain that can fit within the skull. Because of all the folds in the human cerebral cortex, it has a surface area of about 2,500 cm2<\/sup>\u00a0(2.5 ft2<\/sup>). The size and importance of the cerebral cortex is far greater in the human brain than the brains of any other vertebrates, including nonhuman\u00a0primates.<\/p>\nThe Limbic System<\/h3>\n
The limbic system consists of the hypothalamus, thalamus, the hippocampus and amygdala. The structures and interacting areas of the\u00a0limbic system<\/a><\/b>\u00a0are involved in motivation, emotion, learning, and memory.<\/p>\nThalamus and Hypothalamus<\/h4>\n
Several structures are located deep within the brain and are important for communication between the brain and spinal cord (or the rest of the body). These structures include the hypothalamus and thalamus. The diagram below (Figure 8.5.7) shows where these structures are located in the brain. Like the two halves of the cerebrum, the hypothalamus and thalamus exist in two halves, one in each hemisphere.<\/p>\nFigure 8.5.7 Structures deep within the brain include the hypothalamus and thalamus.<\/em><\/figcaption><\/figure>\nThe\u00a0hypothalamus<\/a><\/strong>\u00a0is located just above the brain stem, and is about the size of an almond. The hypothalamus is responsible for certain metabolic processes and other activities of the autonomic nervous system<\/a>, including body\u00a0temperature,\u00a0heart\u00a0rate, hunger, thirst, fatigue, sleep, wakefulness, and circadian (24-hour) rhythms. The hypothalamus is also an important emotional center of the brain. The hypothalamus can regulate so many body functions because it responds to many different internal and external signals, including messages from the brain, light, steroid hormones, stress, and invading pathogens, among others.<\/p>\nOne way the hypothalamus influences body functions is by synthesizing hormones that directly influence body processes. It synthesizes the hormone oxytocin<\/a>, which stimulates uterine contractions during childbirth and the letdown of milk during lactation. It also synthesizes antidiuretic hormone<\/a>, which stimulates the kidneys to reabsorb more water and excrete more concentrated urine. These two hormones are sent from the hypothalamus via a stalk-like structure called the infundibulum (see Figure 8.5.7) directly to the posterior (back) portion of the pituitary gland, which secretes them into the blood.<\/p>\nThe main way the hypothalamus influences body functions is by controlling the\u00a0pituitary gland<\/a>, known as the master gland of the\u00a0endocrine system. The hypothalamus synthesizes neurohormones called releasing factors that travel through the infundibulum directly to the anterior (front) part of the pituitary gland. The releasing factors generally either stimulate or inhibit the secretion of anterior pituitary hormones, most of which control other glands of the endocrine system.<\/p>\n
Midbrain<\/h2>\r\n[caption id=\"attachment_3079\" align=\"alignleft\" width=\"317\"] Figure 8.5.5 The brainstem includes the midbrain, the pons and the medulla oblongata.<\/em>[\/caption]\r\n\r\nThe midbrain is the topmost part of the brainstem and is the essential connection between and brain and spinal cord.\u00a0 The three main parts of the midbrain are the colliculi, the tegmentum, and the cerebral peduncles.\u00a0 These structures are all considered part of the brainstem, which consists of the medulla oblongata, the pons and the midbrain.\r\nReticular Activating System<\/h3>\r\nThe [pb_glossary id=\"3082\"]reticular activating system[\/pb_glossary] (RAS) is responsible for the sleep-wake cycle and wakefulness.\u00a0 It also regulates attention, ability to focus and arousal.\r\nForebrain<\/h2>\r\nThe forebrain is the anterior (forwardmost) part of the brain and includes the cerebrum, the thalamus and hypothalamus, hippocampus, amygdala, and limbic system.\u00a0 This portion of the brain is responsible for processing incoming sensory information, performing complex cognitive activities (speech, abstract thought, etc) and governing voluntary motor movements.\u00a0 \u00a0The forebrain also controls body temperature, reproductive functions, eating, sleeping and the display of emotions.\r\nCerebrum<\/h3>\r\nThe\u00a0[pb_glossary id=\"5941\"]cerebrum[\/pb_glossary]<\/strong>\u00a0is the largest part of the brain. It controls conscious, intellectual functions.\u00a0Among other things,\u00a0it controls reasoning, language, memory, sight, touch, and hearing. When you read a book, play a video game, or recognize a classmate, you are using your cerebrum.\r\nHemispheres and Lateralization of the Cerebrum<\/h4>\r\nThe cerebrum is divided from front to back into two halves called the left and right\u00a0[pb_glossary id=\"3083\"]hemispheres[\/pb_glossary].<\/strong>\u00a0The two hemispheres are connected by a thick bundle of axons, known as the [pb_glossary id=\"5955\"]corpus callosum[\/pb_glossary], which lies deep within the brain. The corpus callosum is the main avenue of\u00a0communication between the two hemispheres. It connects each point in the cerebrum to the mirror-image point in the opposite hemisphere.\r\n\r\nThe right and left hemispheres of the cerebrum are similar in shape, and most areas of cerebrum are found in both hemispheres. Some areas, however, show\u00a0[pb_glossary id=\"3085\"]lateralization[\/pb_glossary],<\/strong>\u00a0or a\u00a0concentration\u00a0in one hemisphere or the other.\u00a0In most people, for example, language functions are more concentrated in the left hemisphere, whereas abstract reasoning and visual-spatial abilities are more concentrated in the right hemisphere.\r\n\r\nFor reasons that are not yet clear, each hemisphere of the brain interacts primarily with the opposite side of the body. The left side of the brain receives messages from and sends commands to the right side of the body, and the right side of the brain\u00a0receives messages from and sends commands to the left side of the body. Sensory nerves from the spinal cord to the brain and motor nerves from the brain to the spinal cord both cross the midline of the body at the level of the brain stem.\r\nLobes of the Cerebrum<\/h4>\r\nEach [pb_glossary id=\"3083\"]hemisphere[\/pb_glossary] of the cerebrum is further divided into the four lobes shown in Figure 8.5.6 and described below.\r\n\r\n[caption id=\"attachment_3086\" align=\"aligncenter\" width=\"680\"] Figure 8.5.6 The cerebrum is organized into four lobes: frontal, parietal, occipital, and temporal.<\/em>[\/caption]\r\n\r\n\r\n\r\nEach hemisphere of the cerebrum consists of four parts, called lobes. Each lobe is associated with particular brain functions. Just one function of each lobe is listed here.\r\n\r\n<\/div>\r\n\r\n \t- The\u00a0[pb_glossary id=\"6021\"]frontal lobes[\/pb_glossary]<\/strong>\u00a0are located at the front of the brain behind the forehead. The frontal lobes are associated with executive functions, such as attention, self-control, planning, problem solving, reasoning, abstract thought, language, and personality.<\/li>\r\n \t
- The\u00a0[pb_glossary id=\"3088\"]parietal lobes[\/pb_glossary]<\/strong>\u00a0are located behind the frontal lobes at the top of the head. The parietal lobes are involved in sensation \u2014 including\u00a0temperature, touch, and taste. Reading and arithmetic are also functions of the parietal lobes.<\/li>\r\n \t
- The\u00a0[pb_glossary id=\"3089\"]temporal lobes[\/pb_glossary]<\/strong>\u00a0are located at the sides of the head below the frontal and parietal lobes. The temporal lobes enable hearing, the formation and retrieval of memories, and the integration of memories and sensations.<\/li>\r\n \t
- The\u00a0[pb_glossary id=\"3090\"]occipital lobes[\/pb_glossary]<\/strong>\u00a0are located at the back of the head below the parietal lobes. The occipital lobes are the smallest of the four pairs of lobes. They are dedicated almost solely to\u00a0vision.<\/li>\r\n<\/ul>\r\n
Cerebral Cortex<\/h4>\r\nMost of the information processing in the brain actually takes place in the\u00a0[pb_glossary id=\"5937\"]cerebral cortex[\/pb_glossary]<\/strong>, a rind of gray matter and other tissues just a few millimetres thick that makes up the outer surface of the cerebrum in both hemispheres of the brain. The cerebral cortex has many folds in it, greatly increasing the amount of surface area of the brain that can fit within the skull. Because of all the folds in the human cerebral cortex, it has a surface area of about 2,500 cm2<\/sup>\u00a0(2.5 ft2<\/sup>). The size and importance of the cerebral cortex is far greater in the human brain than the brains of any other vertebrates, including nonhuman\u00a0primates.\r\nThe Limbic System<\/h3>\r\nThe limbic system consists of the hypothalamus, thalamus, the hippocampus and amygdala. The structures and interacting areas of the\u00a0[pb_glossary id=\"3098\"]limbic system[\/pb_glossary]<\/b>\u00a0are involved in motivation, emotion, learning, and memory.\r\nThalamus and Hypothalamus<\/h4>\r\nSeveral structures are located deep within the brain and are important for communication between the brain and spinal cord (or the rest of the body). These structures include the hypothalamus and thalamus. The diagram below (Figure 8.5.7) shows where these structures are located in the brain. Like the two halves of the cerebrum, the hypothalamus and thalamus exist in two halves, one in each hemisphere.\r\n\r\n[caption id=\"attachment_3092\" align=\"alignleft\" width=\"363\"] Figure 8.5.7 Structures deep within the brain include the hypothalamus and thalamus.<\/em>[\/caption]\r\n\r\nThe\u00a0[pb_glossary id=\"2937\"]hypothalamus[\/pb_glossary]<\/strong>\u00a0is located just above the brain stem, and is about the size of an almond. The hypothalamus is responsible for certain metabolic processes and other activities of the [pb_glossary id=\"5899\"]autonomic nervous system[\/pb_glossary], including body\u00a0temperature,\u00a0heart\u00a0rate, hunger, thirst, fatigue, sleep, wakefulness, and circadian (24-hour) rhythms. The hypothalamus is also an important emotional center of the brain. The hypothalamus can regulate so many body functions because it responds to many different internal and external signals, including messages from the brain, light, steroid hormones, stress, and invading pathogens, among others.\r\n\r\nOne way the hypothalamus influences body functions is by synthesizing hormones that directly influence body processes. It synthesizes the hormone [pb_glossary id=\"3093\"]oxytocin[\/pb_glossary], which stimulates uterine contractions during childbirth and the letdown of milk during lactation. It also synthesizes [pb_glossary id=\"5893\"]antidiuretic hormone[\/pb_glossary], which stimulates the kidneys to reabsorb more water and excrete more concentrated urine. These two hormones are sent from the hypothalamus via a stalk-like structure called the infundibulum (see Figure 8.5.7) directly to the posterior (back) portion of the pituitary gland, which secretes them into the blood.\r\n\r\nThe main way the hypothalamus influences body functions is by controlling the\u00a0[pb_glossary id=\"2938\"]pituitary gland[\/pb_glossary], known as the master gland of the\u00a0endocrine system. The hypothalamus synthesizes neurohormones called releasing factors that travel through the infundibulum directly to the anterior (front) part of the pituitary gland. The releasing factors generally either stimulate or inhibit the secretion of anterior pituitary hormones, most of which control other glands of the endocrine system.\r\n\r\nThe\u00a0[pb_glossary id=\"3095\"]thalamus[\/pb_glossary],<\/strong> which is located near the hypothalamus (see Figure 8.5.7), is a major hub for information traveling back and forth between the spinal cord and cerebrum. It relays sensory signals to the cerebral cortex and motor signals to the spinal cord. It is also involved in the regulation of consciousness, sleep, and alertness.\r\n\r\nHippocampus and Amygdala<\/h4>\r\nThe [pb_glossary id=\"3096\"]hippocampus[\/pb_glossary] is a complex structure embedded deep in the temporal lobe.\u00a0 It plays a major role in learning and memory and contributes to regulation of motivation and emotion. The amygdala is the part of the brain responsible for formation and storage of memories associated with emotional events.\r\n\r\nWatch \"The Limbic System\" by Soton Brain Hub to learn about the location and functions of the limbic system.\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=jcrWPo_s6EE\r\n
The Limbic System, Soton Brain Hub, 2016.<\/p>\r\n\r\n
Spinal Cord<\/h1>\r\n<\/div>\r\nThe\u00a0[pb_glossary id=\"3010\"]spinal cord[\/pb_glossary]<\/strong> is a long, thin, tubular bundle of nervous tissues that extends from the brain stem and continues down the center of the back to the pelvis. It is highlighted in yellow in Figure 8.5.8. The spinal cord is enclosed within, but is shorter than, the vertebral column.\r\n\r\n[caption id=\"attachment_3099\" align=\"alignnone\" width=\"482\"] Figure 8.5.8 The spinal cord (yellow) runs from the bottom of the brain to the lower back.<\/em>[\/caption]\r\nStructure of the Spinal Cord<\/h2>\r\nThe center of the spinal cord consists of gray matter, which is made up mainly of cell bodies of neurons, including interneurons and motor neurons. The gray matter is surrounded by white matter that consists mainly of myelinated axons of motor and sensory neurons. Spinal nerves, which connect the spinal cord to the PNS, exit from the spinal cord between vertebrae (see Figure 8.5.9).\r\n\r\n \r\n\r\n\r\n[caption id=\"attachment_3100\" align=\"alignleft\" width=\"291\"] Figure 8.5.9 This model shows three vertebrae (white) with branching spinal nerves (yellow) emerging from the either side of the spinal cord between vertebrae.<\/em>[\/caption]\r\n\r\n<\/div>\r\nFunctions of the Spinal Cord<\/h2>\r\nThe spinal cord serves as an information superhighway. It passes messages from the body to the brain and from the brain to the body. Sensory (afferent) nerves carry\u00a0nerve impulses\u00a0to the brain from sensory receptor\u00a0cells\u00a0everywhere in and on the body. Motor (efferent) nerves carry nerve impulses away from the brain to glands, organs, or\u00a0muscles throughout the body.\r\n\r\nThe spinal cord also independently controls certain rapid responses called\u00a0reflexes<\/strong> without any input from the brain. You can see how this may happen in Figure 8.5.10. A sensory receptor responds to a sensation and sends a nerve impulse along a sensory nerve to the spinal cord. In the spinal cord, the message passes to an interneuron and from the interneuron to a motor nerve, which carries the impulse to a muscle. The muscle contracts in response. These neuron connections form a reflex arc, which requires no input from the brain. No doubt you have experienced such reflex actions yourself. For example, you may have reached out to touch a pot on the stove, not realizing that it was very hot. Virtually at the same moment that you feel the burning heat, you jerk your arm back and remove your hand from the pot.\r\n\r\n \r\n\r\n\r\n[caption id=\"attachment_3101\" align=\"alignnone\" width=\"1038\"] Figure 8.5.10 This diagram shows what happens in a long reflex (top), in which sensory nerves carry the message all the way to the spinal cord; and in a short reflex (bottom), in which sensory nerves travel only to a ganglion outside the spinal cord. Note that interneurons are involved in reflexes, connecting sensory and motor neurons, but they are not actually shown in the diagram.<\/em>[\/caption]\r\n\r\n<\/div>\r\nInjuries to the Spinal Cord<\/h2>\r\nPhysical damage to the spinal cord may result in\u00a0[pb_glossary id=\"3102\"]paralysis[\/pb_glossary],<\/strong> which is loss of sensation and movement in part of the body. Paralysis generally affects all the areas of the body below the level of the injury, because nerve impulses are interrupted and can no longer travel back and forth between the brain and body beyond that point. If an injury to the spinal cord produces nothing more than swelling, the symptoms may be transient. However, if nerve fibres (axons) in the spinal cord are badly damaged, the loss of function may be permanent. Experimental studies have shown that spinal nerve fibres attempt to regrow, but tissue destruction usually produces scar tissue that cannot be penetrated by the regrowing nerves, as well other factors that inhibit nerve fibre regrowth in the central nervous system.\r\n\r\nFeature: My\u00a0Human Body<\/h1>\r\n<\/div>\r\nEach year, many millions of people have a stroke<\/a>, and stroke is the second leading cause of death in adults.\u00a0[pb_glossary id=\"3103\"]Stroke[\/pb_glossary],<\/strong>\u00a0also known as cerebrovascular accident, occurs when poor blood flow to the brain results in the death of brain cells. There are two main types of strokes:\r\n\r\n \t- Ischemic strokes occur due to lack of blood flow because of a blood clot in an artery going to the brain.<\/li>\r\n \t
- Hemorrhagic strokes occur due to bleeding from a broken blood vessel in the brain.<\/li>\r\n<\/ul>\r\nEither type of stroke may result in paralysis, loss of the ability to speak or comprehend speech, loss of bladder control, personality changes, and many other potential effects, depending on the part of the brain that is injured. The effects of a stroke may be mild and transient or more severe and permanent. A stroke may even be fatal. It generally depends on the type of stroke and how extensive it is.\r\n\r\nAre you at risk of a stroke? The main risk factor for stroke is age \u2014 about two-thirds of strokes occur in people over the age of 65. There is nothing you can do about your age, but most other stroke risk factors can be reduced with lifestyle changes or medications. The risk factors include high blood pressure, tobacco smoking, obesity, high blood cholesterol, diabetes mellitus, and atrial fibrillation.\r\n\r\nChances are good that you or someone you know is at risk of a stroke, so it is important to recognize a stroke if one occurs. A stroke is a medical emergency, and the more quickly treatment is given, the better the outcome is likely to be. In the case of ischemic strokes, the use of clot-busting drugs may prevent permanent brain damage if administered within three or four hours of the stroke. Remembering the signs of a stroke is easy. They are summed up by the acronym FAST.\r\n\r\n
\r\n8.5 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- The [pb_glossary id=\"5933\"]central nervous system[\/pb_glossary] is the part of the nervous system that includes the [pb_glossary id=\"5915\"]brain[\/pb_glossary] and [pb_glossary id=\"3010\"]spinal cord[\/pb_glossary]. It is physically protected by\u00a0bones, meninges, and [pb_glossary id=\"5939\"]cerebrospinal fluid[\/pb_glossary]. It is chemically protected by the blood-brain barrier.<\/li>\r\n \t
- The brain is the control center of the nervous system and of the entire organism. The brain uses a relatively large proportion of the body\u2019s\u00a0energy, primarily in the form of glucose.<\/li>\r\n \t
- The brain is divided into three major parts, each with different functions: the hindbrain, the midbrain and the forebrain.<\/li>\r\n \t
- Hindbrain consists of the medulla oblongata, the pons and the cerebellum, each of which perform specific functions.<\/li>\r\n \t
- The midbrain is primarily responsible for motor movement and in auditory and visual processing.<\/li>\r\n \t
- The forebrain contains many structures including:\r\n
\r\n \t- The cerebrum, which is further divided into left and right hemispheres. Each hemisphere has four lobes: frontal, parietal, temporal, and occipital. Each lobe is associated with specific senses or other functions.<\/li>\r\n \t
- The cerebrum\u00a0has a\u00a0thin outer layer called the cerebral cortex. Its many folds give it a large surface area. This is where most information processing takes place.<\/li>\r\n \t
- Inner structures of the brain include the hypothalamus \u2014 which controls the\u00a0endocrine system\u00a0via the\u00a0pituitary gland\u00a0\u2014 and the thalamus, which has several involuntary functions.<\/li>\r\n \t
- The hippocampus and amygdala, which are part of the limbic system and play important roles in memory, learning and emotions.<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t
- The spinal cord is a tubular bundle of nervous tissues that extends from the head down the middle of the back to the pelvis. It functions mainly to connect the brain with the\u00a0peripheral nervous system. It also controls certain rapid responses called reflexes without any input from the brain.<\/li>\r\n \t
- A spinal cord injury may lead to paralysis (loss of sensation and movement) of the body below the level of the injury, because nerve impulses can no longer travel up and down the spinal cord beyond that point.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n8.5 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- What is the central nervous system?<\/li>\r\n \t
- How is the central nervous system protected?<\/li>\r\n \t
- What is the overall function of the brain?<\/li>\r\n \t
- Identify the three main parts of the brain and one function of each part.<\/li>\r\n \t
- Describe the hemispheres of the brain.<\/li>\r\n \t
- Explain and give examples of lateralization of the brain.<\/li>\r\n \t
- Identify one function of each of the four lobes of the cerebrum.<\/li>\r\n \t
- [h5p id=\"562\"]<\/li>\r\n \t
- [h5p id=\"563\"]<\/li>\r\n \t
- Summarize the structure and function of the cerebral cortex. Explain how the hypothalamus controls the endocrine system.<\/li>\r\n \t
- Describe the spinal cord.<\/li>\r\n \t
- What is the main function of the spinal cord?<\/li>\r\n \t
- Explain how reflex actions occur.<\/li>\r\n \t
- Why do severe spinal cord injuries usually cause paralysis?<\/li>\r\n \t
- What do you think are some possible consequences of severe damage to the brain stem? How might this compare to the consequences of severe damage to the frontal lobe? Explain your answer.<\/li>\r\n \t
- Information travels very quickly in the nervous system, but generally, the longer the path between areas, the longer it takes. Based on this, explain why you think reflexes often occur at the spinal cord level, and do not require input from the brain.<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
\r\n8.5 Explore More<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=sewhbmh0ECg\r\nWhat if we could look inside human brains? - Moran Cerf, TED-Ed, 2013.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=ZMSbDwpIyF4\r\n
The left brain vs. right brain myth - Elizabeth Waters, TED-Ed, 2017.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?time_continue=1&v=aCv4K5aStdU&feature=emb_logo\r\n
Split-brain patient 'Joe' being tested with stimuli presented in different visual fields,\r\nmarkmcdermott, 2010.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n
Attributes<\/h2>\r\nFigure 8.5.1<\/strong>\r\n\r\nSensory_Homunculus-en.svg<\/a> by Popadius<\/a> on Wikimedia Commons is used under a CC BY 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0\/deed.en) license. (This is a derivative work from File:1421 Sensory Homunculus<\/a>.jpg by OpenStax College<\/a>)\r\n\r\nFigure 8.5.2<\/strong>\r\n\r\nOverview_of_Nervous_System<\/a>\u00a0by OpenStax<\/a> on Wikimedia Commons is used under a CC BY 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en) license.\r\n\r\nFigure 8.5.3<\/strong>\r\n\r\nDiagram_showing_the_brain_stem_which_includes_the_medulla_oblongata,_the_pons_and_the_midbrain_(2)_CRUK_294.svg<\/a> by Cancer Research UK<\/a> on Wikimedia Commons is used under a CC BY-SA 4.0 <\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\nFigure 8.5.4<\/strong>\r\n\r\nBrain_bulbar_region.svg<\/a> by Fvasconcellos<\/a> on Wikimedia Commons is used under a CC BY 2.5<\/a> license (derivative work from Brain human sagittal section.svg<\/a>\u00a0 by Patrick J. Lynch; Brain bulbar region.PNG<\/a> by DO11.10<\/a>).\r\n\r\nFigure 8.5.5<\/strong>\r\n\r\nMidbrain<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY 3.0 <\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0) license.\r\n\r\nFigure 8.5.6<\/strong>\r\n\r\nBrainLobes<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY 3.0 <\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0) license.\u00a0<\/span>\r\n\r\nFigure 8.5.7<\/strong>\r\n\r\nDiencephalon<\/a> by OpenStax<\/a> Wikimedia Commons is used under a CC BY 4.0 <\/a>(https:\/\/creativecommons.org\/licenses\/by\/4.0) license.\r\n\r\nFigure 8.5.8<\/strong>\r\n\r\nSpinalCord<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY 3.0 <\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0) license.\u00a0<\/span>\r\n\r\nFigure 8.5.9<\/strong>\r\n\r\nSpinal_readjustment_3<\/a> by Tomwsulcer<\/a> on\u00a0 Wikimedia Commons is used under a CC0 1.0<\/a> Universal Public Domain Dedication license (https:\/\/creativecommons.org\/publicdomain\/zero\/1.0\/deed.en).\r\n\r\nFigure 8.5.10<\/strong>\r\n\r\n1507_Short_and_Long_Reflexes<\/a> by OpenStax<\/a> on Wikimedia Commons is used under a CC BY 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en) license.\r\nReferences<\/h2>\r\n
Betts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2013, 28 May). Figure 14.23<\/span>\u00a0<\/span>The sensory homunculus <\/span>[digital image]. In Anatomy and Physiology<\/em> (Section 14.2). OpenStax. https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/14-2-central-processing\r\n<\/span><\/span><\/p>\r\nBetts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2013, 28 May). Figure 15.8 Short and long reflexes [digital image]. In Anatomy and Physiology<\/em> (Section 15.2). OpenStax. https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/15-2-autonomic-reflexes-and-homeostasis<\/p>\r\nBetts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2016, May 18). <\/span><\/span>Figure 12.2 Central and peripheral nervous system [digital image]. In Anatomy and Physiology<\/em> (Section 12.1). https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/12-1-basic-structure-and-function-of-the-nervous-system<\/span><\/span><\/p>\r\nBetts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2016, May 18). Figure 13.11 The diencephalon [digital image]. In Anatomy and Physiology<\/em> (Section 13.2). https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/13-2-the-central-nervous-system<\/p>\r\nBlausen.com staff. (2014). Medical gallery of Blausen Medical 2014. WikiJournal of Medicine,<\/em> 1<\/em> (2). DOI:10.15347\/wjm\/2014.010. ISSN 2002-4436<\/span><\/p>\r\nmarkmcdermott. (2010). Split-brain patient 'Joe' being tested with stimuli presented in different visual fields. YouTube. https:\/\/www.youtube.com\/user\/markmcdermott\/search?query=split<\/p>\r\n
Mayo Clinic Staff. (n.d.). Stroke [online article]. MayoClinic.org. https:\/\/www.mayoclinic.org\/diseases-conditions\/stroke\/symptoms-causes\/syc-20350113<\/p>\r\n
Soton Brain Hub. (2016, July 29). The limbic system. YouTube. https:\/\/www.youtube.com\/watch?v=jcrWPo_s6EE&feature=youtu.be<\/p>\r\n
TED-Ed. (2013, January 31). What if we could look inside human brains? - Moran Cerf. YouTube. https:\/\/www.youtube.com\/watch?v=sewhbmh0ECg&feature=youtu.be<\/p>\r\n
TED-Ed. (2017, July 24). The left brain vs. right brain myth - Elizabeth Waters. YouTube. https:\/\/www.youtube.com\/watch?v=ZMSbDwpIyF4&feature=youtu.be<\/p>\r\n ","rendered":"
<\/p>\nFigure 8.5.1 This picture is called an <\/em>homunculus.\u00a0<\/em><\/figcaption><\/figure>\nHomunculus<\/h1>\n
The very odd-looking drawing in Figure 8.5.1 is called a homunculus. The beige mass represents a cross-sectional wedge of the human brain, and the drawing shows some areas of the brain associated with different parts of the body. As you can see, larger areas of the brain in this region are associated with the hands, face, and tongue, as compared to the areas associated with the legs and feet. Given the importance of speech, manual dexterity, and face-to-face social interactions in human beings, it is not surprising that relatively large areas of the brain are needed to control these body parts. The brain is the most complex organ in the human body and part of the central nervous system.<\/p>\n
\nWhat Is the Central Nervous System?<\/h1>\n<\/div>\n
The central nervous system<\/a> (CNS) is the part of the nervous system that includes the brain<\/a> and spinal cord<\/a>. The drawing below (Figure 8.5.2) shows the central nervous system as one of two main divisions of the total nervous system. The other main division is the peripheral nervous system<\/a> (PNS). The CNS and PNS work together to control virtually all body functions.<\/p>\nFigure 8.5.2 The two main divisions of the nervous system: the central nervous system (CNS) \u2014 which includes the brain and spinal cord \u2014 and the peripheral nervous system (PNS), which includes nerves and ganglia (singular, ganglion), which transmit information between the CNS to the rest of the body.<\/em><\/figcaption><\/figure>\nThe delicate nervous tissues of the central nervous system are protected by major physical and chemical barriers. Physically, the brain and spinal cord are surrounded by tough meninges<\/a>, a three-layer protective sheath that also contains cushioning cerebrospinal fluid<\/a>. The\u00a0bones\u00a0of the skull and spinal vertebrae also contribute to physically protecting the brain and spinal cord. Chemically, the brain and spinal cord are isolated from the circulation\u00a0\u2014\u00a0and most toxins or pathogens in the\u00a0blood\u00a0\u2014\u00a0by the\u00a0blood-brain barrier<\/a>.<\/strong>\u00a0The blood-brain barrier is a highly selective membrane formed of endothelial\u00a0cells\u00a0that separates the circulating\u00a0blood\u00a0from extracellular fluid in the CNS. The barrier allows\u00a0water, certain gases, glucose, and some other molecules needed by the brain and spinal cord to cross from the blood into the CNS, while keeping out potentially harmful substances. These physical and chemical barriers make the CNS less susceptible to injury than the PNS. However, damage to the CNS is likely to have more serious consequences.<\/p>\n\nThe Brain<\/h1>\n<\/div>\n
The\u00a0brain<\/a><\/strong> is the control center of not only the rest of the nervous system, but of the entire organism. The adult brain makes up only about 2% of the body\u2019s weight, but it uses about 20% of the body\u2019s total energy. The brain contains an estimated 100 billion neurons, and each neuron<\/a> has thousands of synaptic connections to other neurons. The brain also has about the same number of neuroglia<\/a> as neurons. No wonder the brain uses so much energy! In addition, the brain uses mostly glucose<\/a> for energy. As a result, if the brain is deprived of glucose, it can lead to unconsciousness. The brain is able to store some glucose in the form of glycogen, but in much smaller amounts than are found in the liver and skeletal muscles.<\/p>\nThe brain controls such mental processes as reasoning, imagination, memory, and language. It also interprets information from the senses and commands the body to respond appropriately. It controls basic physical processes (such as breathing and heartbeat), as well as voluntary activities (such as walking and writing). The brain has three major regions: the hindbrain, the midbrain and the forebrain. These parts are shown in Figure 8.5.3 and described below.<\/p>\nFigure 8.5.3 Diagram of the forebrain, midbrain and hindbrain. <\/em><\/figcaption><\/figure>\n\n <\/p>\n<\/div>\n
The Hindbrain<\/h2>\nFigure 8.5.4 The hindbrain consists of the cerebellum,<\/em> medulla oblongata, and the pons. It plays the extremely important role of connecting the brain to the rest of the body via the spinal cord.<\/em><\/figcaption><\/figure>\nThe\u00a0hindbrain<\/a>, <\/strong>which includes the cerebellum<\/a>, medulla oblongata<\/a>, and the pons<\/a>. The hindbrain is the lowest part of the brain. It resembles a stalk and platform on which the cerebrum is perched. The components of the hindbrain connect the rest of the brain with the spinal cord and passes nerve impulses between the brain and spinal cord.<\/p>\nCerebellum<\/h3>\n
The\u00a0cerebellum<\/a><\/strong> is located just below the cerebrum and at the back of the brain behind the brain stem. It coordinates your voluntary movements, balance, and posture.\u00a0 Information from your inner ear, joints and muscles, and eyes are all knitted together in the cerebellum so that you have awareness of where you are in 3-dimensional space.\u00a0 Patients who have suffered damage to their cerebellum may suffer from balance disorder. In addition the cerebellum plays a major role in motor learning (like how to ride a bike or how to do a backflip on a trampoline) through trial and error.\u00a0 While traditionally, the cerebellum was thought to only be involved in motor functions, we now know that it also plays an important role in memory and learning.<\/p>\nMedulla Oblongata<\/h3>\n
The\u00a0medulla oblongata<\/a><\/strong> makes up part of the brainstem and sits in front of and just below the cerebellum, at the very top of the spinal cord.\u00a0 It is responsible for control of heart rate, respiration rate and blood pressure, as well as reflexes such as vomiting, coughing, sneezing and swallowing.<\/p>\nPons<\/h3>\n
The\u00a0pons<\/a><\/strong> is located in front of the cerebellum and above the medulla oblongata.\u00a0 It has several functions, including receiving sensory information from the face, regulating rate and depth of breaths, as well as sleep cycles.<\/p>\nMidbrain<\/h2>\nFigure 8.5.5 The brainstem includes the midbrain, the pons and the medulla oblongata.<\/em><\/figcaption><\/figure>\nThe midbrain is the topmost part of the brainstem and is the essential connection between and brain and spinal cord.\u00a0 The three main parts of the midbrain are the colliculi, the tegmentum, and the cerebral peduncles.\u00a0 These structures are all considered part of the brainstem, which consists of the medulla oblongata, the pons and the midbrain.<\/p>\n
Reticular Activating System<\/h3>\n
The reticular activating system<\/a> (RAS) is responsible for the sleep-wake cycle and wakefulness.\u00a0 It also regulates attention, ability to focus and arousal.<\/p>\nForebrain<\/h2>\n
The forebrain is the anterior (forwardmost) part of the brain and includes the cerebrum, the thalamus and hypothalamus, hippocampus, amygdala, and limbic system.\u00a0 This portion of the brain is responsible for processing incoming sensory information, performing complex cognitive activities (speech, abstract thought, etc) and governing voluntary motor movements.\u00a0 \u00a0The forebrain also controls body temperature, reproductive functions, eating, sleeping and the display of emotions.<\/p>\n
Cerebrum<\/h3>\n
The\u00a0cerebrum<\/a><\/strong>\u00a0is the largest part of the brain. It controls conscious, intellectual functions.\u00a0Among other things,\u00a0it controls reasoning, language, memory, sight, touch, and hearing. When you read a book, play a video game, or recognize a classmate, you are using your cerebrum.<\/p>\nHemispheres and Lateralization of the Cerebrum<\/h4>\n
The cerebrum is divided from front to back into two halves called the left and right\u00a0hemispheres<\/a>.<\/strong>\u00a0The two hemispheres are connected by a thick bundle of axons, known as the corpus callosum<\/a>, which lies deep within the brain. The corpus callosum is the main avenue of\u00a0communication between the two hemispheres. It connects each point in the cerebrum to the mirror-image point in the opposite hemisphere.<\/p>\nThe right and left hemispheres of the cerebrum are similar in shape, and most areas of cerebrum are found in both hemispheres. Some areas, however, show\u00a0lateralization<\/a>,<\/strong>\u00a0or a\u00a0concentration\u00a0in one hemisphere or the other.\u00a0In most people, for example, language functions are more concentrated in the left hemisphere, whereas abstract reasoning and visual-spatial abilities are more concentrated in the right hemisphere.<\/p>\nFor reasons that are not yet clear, each hemisphere of the brain interacts primarily with the opposite side of the body. The left side of the brain receives messages from and sends commands to the right side of the body, and the right side of the brain\u00a0receives messages from and sends commands to the left side of the body. Sensory nerves from the spinal cord to the brain and motor nerves from the brain to the spinal cord both cross the midline of the body at the level of the brain stem.<\/p>\n
Lobes of the Cerebrum<\/h4>\n
Each hemisphere<\/a> of the cerebrum is further divided into the four lobes shown in Figure 8.5.6 and described below.<\/p>\nFigure 8.5.6 The cerebrum is organized into four lobes: frontal, parietal, occipital, and temporal.<\/em><\/figcaption><\/figure>\n\nEach hemisphere of the cerebrum consists of four parts, called lobes. Each lobe is associated with particular brain functions. Just one function of each lobe is listed here.<\/p>\n<\/div>\n
\n- The\u00a0frontal lobes<\/a><\/strong>\u00a0are located at the front of the brain behind the forehead. The frontal lobes are associated with executive functions, such as attention, self-control, planning, problem solving, reasoning, abstract thought, language, and personality.<\/li>\n
- The\u00a0parietal lobes<\/a><\/strong>\u00a0are located behind the frontal lobes at the top of the head. The parietal lobes are involved in sensation \u2014 including\u00a0temperature, touch, and taste. Reading and arithmetic are also functions of the parietal lobes.<\/li>\n
- The\u00a0temporal lobes<\/a><\/strong>\u00a0are located at the sides of the head below the frontal and parietal lobes. The temporal lobes enable hearing, the formation and retrieval of memories, and the integration of memories and sensations.<\/li>\n
- The\u00a0occipital lobes<\/a><\/strong>\u00a0are located at the back of the head below the parietal lobes. The occipital lobes are the smallest of the four pairs of lobes. They are dedicated almost solely to\u00a0vision.<\/li>\n<\/ul>\n
Cerebral Cortex<\/h4>\n
Most of the information processing in the brain actually takes place in the\u00a0cerebral cortex<\/a><\/strong>, a rind of gray matter and other tissues just a few millimetres thick that makes up the outer surface of the cerebrum in both hemispheres of the brain. The cerebral cortex has many folds in it, greatly increasing the amount of surface area of the brain that can fit within the skull. Because of all the folds in the human cerebral cortex, it has a surface area of about 2,500 cm2<\/sup>\u00a0(2.5 ft2<\/sup>). The size and importance of the cerebral cortex is far greater in the human brain than the brains of any other vertebrates, including nonhuman\u00a0primates.<\/p>\nThe Limbic System<\/h3>\n
The limbic system consists of the hypothalamus, thalamus, the hippocampus and amygdala. The structures and interacting areas of the\u00a0limbic system<\/a><\/b>\u00a0are involved in motivation, emotion, learning, and memory.<\/p>\nThalamus and Hypothalamus<\/h4>\n
Several structures are located deep within the brain and are important for communication between the brain and spinal cord (or the rest of the body). These structures include the hypothalamus and thalamus. The diagram below (Figure 8.5.7) shows where these structures are located in the brain. Like the two halves of the cerebrum, the hypothalamus and thalamus exist in two halves, one in each hemisphere.<\/p>\nFigure 8.5.7 Structures deep within the brain include the hypothalamus and thalamus.<\/em><\/figcaption><\/figure>\nThe\u00a0hypothalamus<\/a><\/strong>\u00a0is located just above the brain stem, and is about the size of an almond. The hypothalamus is responsible for certain metabolic processes and other activities of the autonomic nervous system<\/a>, including body\u00a0temperature,\u00a0heart\u00a0rate, hunger, thirst, fatigue, sleep, wakefulness, and circadian (24-hour) rhythms. The hypothalamus is also an important emotional center of the brain. The hypothalamus can regulate so many body functions because it responds to many different internal and external signals, including messages from the brain, light, steroid hormones, stress, and invading pathogens, among others.<\/p>\nOne way the hypothalamus influences body functions is by synthesizing hormones that directly influence body processes. It synthesizes the hormone oxytocin<\/a>, which stimulates uterine contractions during childbirth and the letdown of milk during lactation. It also synthesizes antidiuretic hormone<\/a>, which stimulates the kidneys to reabsorb more water and excrete more concentrated urine. These two hormones are sent from the hypothalamus via a stalk-like structure called the infundibulum (see Figure 8.5.7) directly to the posterior (back) portion of the pituitary gland, which secretes them into the blood.<\/p>\nThe main way the hypothalamus influences body functions is by controlling the\u00a0pituitary gland<\/a>, known as the master gland of the\u00a0endocrine system. The hypothalamus synthesizes neurohormones called releasing factors that travel through the infundibulum directly to the anterior (front) part of the pituitary gland. The releasing factors generally either stimulate or inhibit the secretion of anterior pituitary hormones, most of which control other glands of the endocrine system.<\/p>\n
Forebrain<\/h2>\r\nThe forebrain is the anterior (forwardmost) part of the brain and includes the cerebrum, the thalamus and hypothalamus, hippocampus, amygdala, and limbic system.\u00a0 This portion of the brain is responsible for processing incoming sensory information, performing complex cognitive activities (speech, abstract thought, etc) and governing voluntary motor movements.\u00a0 \u00a0The forebrain also controls body temperature, reproductive functions, eating, sleeping and the display of emotions.\r\nCerebrum<\/h3>\r\nThe\u00a0[pb_glossary id=\"5941\"]cerebrum[\/pb_glossary]<\/strong>\u00a0is the largest part of the brain. It controls conscious, intellectual functions.\u00a0Among other things,\u00a0it controls reasoning, language, memory, sight, touch, and hearing. When you read a book, play a video game, or recognize a classmate, you are using your cerebrum.\r\nHemispheres and Lateralization of the Cerebrum<\/h4>\r\nThe cerebrum is divided from front to back into two halves called the left and right\u00a0[pb_glossary id=\"3083\"]hemispheres[\/pb_glossary].<\/strong>\u00a0The two hemispheres are connected by a thick bundle of axons, known as the [pb_glossary id=\"5955\"]corpus callosum[\/pb_glossary], which lies deep within the brain. The corpus callosum is the main avenue of\u00a0communication between the two hemispheres. It connects each point in the cerebrum to the mirror-image point in the opposite hemisphere.\r\n\r\nThe right and left hemispheres of the cerebrum are similar in shape, and most areas of cerebrum are found in both hemispheres. Some areas, however, show\u00a0[pb_glossary id=\"3085\"]lateralization[\/pb_glossary],<\/strong>\u00a0or a\u00a0concentration\u00a0in one hemisphere or the other.\u00a0In most people, for example, language functions are more concentrated in the left hemisphere, whereas abstract reasoning and visual-spatial abilities are more concentrated in the right hemisphere.\r\n\r\nFor reasons that are not yet clear, each hemisphere of the brain interacts primarily with the opposite side of the body. The left side of the brain receives messages from and sends commands to the right side of the body, and the right side of the brain\u00a0receives messages from and sends commands to the left side of the body. Sensory nerves from the spinal cord to the brain and motor nerves from the brain to the spinal cord both cross the midline of the body at the level of the brain stem.\r\nLobes of the Cerebrum<\/h4>\r\nEach [pb_glossary id=\"3083\"]hemisphere[\/pb_glossary] of the cerebrum is further divided into the four lobes shown in Figure 8.5.6 and described below.\r\n\r\n[caption id=\"attachment_3086\" align=\"aligncenter\" width=\"680\"] Figure 8.5.6 The cerebrum is organized into four lobes: frontal, parietal, occipital, and temporal.<\/em>[\/caption]\r\n\r\n\r\n\r\nEach hemisphere of the cerebrum consists of four parts, called lobes. Each lobe is associated with particular brain functions. Just one function of each lobe is listed here.\r\n\r\n<\/div>\r\n\r\n \t- The\u00a0[pb_glossary id=\"6021\"]frontal lobes[\/pb_glossary]<\/strong>\u00a0are located at the front of the brain behind the forehead. The frontal lobes are associated with executive functions, such as attention, self-control, planning, problem solving, reasoning, abstract thought, language, and personality.<\/li>\r\n \t
- The\u00a0[pb_glossary id=\"3088\"]parietal lobes[\/pb_glossary]<\/strong>\u00a0are located behind the frontal lobes at the top of the head. The parietal lobes are involved in sensation \u2014 including\u00a0temperature, touch, and taste. Reading and arithmetic are also functions of the parietal lobes.<\/li>\r\n \t
- The\u00a0[pb_glossary id=\"3089\"]temporal lobes[\/pb_glossary]<\/strong>\u00a0are located at the sides of the head below the frontal and parietal lobes. The temporal lobes enable hearing, the formation and retrieval of memories, and the integration of memories and sensations.<\/li>\r\n \t
- The\u00a0[pb_glossary id=\"3090\"]occipital lobes[\/pb_glossary]<\/strong>\u00a0are located at the back of the head below the parietal lobes. The occipital lobes are the smallest of the four pairs of lobes. They are dedicated almost solely to\u00a0vision.<\/li>\r\n<\/ul>\r\n
Cerebral Cortex<\/h4>\r\nMost of the information processing in the brain actually takes place in the\u00a0[pb_glossary id=\"5937\"]cerebral cortex[\/pb_glossary]<\/strong>, a rind of gray matter and other tissues just a few millimetres thick that makes up the outer surface of the cerebrum in both hemispheres of the brain. The cerebral cortex has many folds in it, greatly increasing the amount of surface area of the brain that can fit within the skull. Because of all the folds in the human cerebral cortex, it has a surface area of about 2,500 cm2<\/sup>\u00a0(2.5 ft2<\/sup>). The size and importance of the cerebral cortex is far greater in the human brain than the brains of any other vertebrates, including nonhuman\u00a0primates.\r\nThe Limbic System<\/h3>\r\nThe limbic system consists of the hypothalamus, thalamus, the hippocampus and amygdala. The structures and interacting areas of the\u00a0[pb_glossary id=\"3098\"]limbic system[\/pb_glossary]<\/b>\u00a0are involved in motivation, emotion, learning, and memory.\r\nThalamus and Hypothalamus<\/h4>\r\nSeveral structures are located deep within the brain and are important for communication between the brain and spinal cord (or the rest of the body). These structures include the hypothalamus and thalamus. The diagram below (Figure 8.5.7) shows where these structures are located in the brain. Like the two halves of the cerebrum, the hypothalamus and thalamus exist in two halves, one in each hemisphere.\r\n\r\n[caption id=\"attachment_3092\" align=\"alignleft\" width=\"363\"] Figure 8.5.7 Structures deep within the brain include the hypothalamus and thalamus.<\/em>[\/caption]\r\n\r\nThe\u00a0[pb_glossary id=\"2937\"]hypothalamus[\/pb_glossary]<\/strong>\u00a0is located just above the brain stem, and is about the size of an almond. The hypothalamus is responsible for certain metabolic processes and other activities of the [pb_glossary id=\"5899\"]autonomic nervous system[\/pb_glossary], including body\u00a0temperature,\u00a0heart\u00a0rate, hunger, thirst, fatigue, sleep, wakefulness, and circadian (24-hour) rhythms. The hypothalamus is also an important emotional center of the brain. The hypothalamus can regulate so many body functions because it responds to many different internal and external signals, including messages from the brain, light, steroid hormones, stress, and invading pathogens, among others.\r\n\r\nOne way the hypothalamus influences body functions is by synthesizing hormones that directly influence body processes. It synthesizes the hormone [pb_glossary id=\"3093\"]oxytocin[\/pb_glossary], which stimulates uterine contractions during childbirth and the letdown of milk during lactation. It also synthesizes [pb_glossary id=\"5893\"]antidiuretic hormone[\/pb_glossary], which stimulates the kidneys to reabsorb more water and excrete more concentrated urine. These two hormones are sent from the hypothalamus via a stalk-like structure called the infundibulum (see Figure 8.5.7) directly to the posterior (back) portion of the pituitary gland, which secretes them into the blood.\r\n\r\nThe main way the hypothalamus influences body functions is by controlling the\u00a0[pb_glossary id=\"2938\"]pituitary gland[\/pb_glossary], known as the master gland of the\u00a0endocrine system. The hypothalamus synthesizes neurohormones called releasing factors that travel through the infundibulum directly to the anterior (front) part of the pituitary gland. The releasing factors generally either stimulate or inhibit the secretion of anterior pituitary hormones, most of which control other glands of the endocrine system.\r\n\r\nThe\u00a0[pb_glossary id=\"3095\"]thalamus[\/pb_glossary],<\/strong> which is located near the hypothalamus (see Figure 8.5.7), is a major hub for information traveling back and forth between the spinal cord and cerebrum. It relays sensory signals to the cerebral cortex and motor signals to the spinal cord. It is also involved in the regulation of consciousness, sleep, and alertness.\r\n\r\nHippocampus and Amygdala<\/h4>\r\nThe [pb_glossary id=\"3096\"]hippocampus[\/pb_glossary] is a complex structure embedded deep in the temporal lobe.\u00a0 It plays a major role in learning and memory and contributes to regulation of motivation and emotion. The amygdala is the part of the brain responsible for formation and storage of memories associated with emotional events.\r\n\r\nWatch \"The Limbic System\" by Soton Brain Hub to learn about the location and functions of the limbic system.\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=jcrWPo_s6EE\r\n
The Limbic System, Soton Brain Hub, 2016.<\/p>\r\n\r\n
Spinal Cord<\/h1>\r\n<\/div>\r\nThe\u00a0[pb_glossary id=\"3010\"]spinal cord[\/pb_glossary]<\/strong> is a long, thin, tubular bundle of nervous tissues that extends from the brain stem and continues down the center of the back to the pelvis. It is highlighted in yellow in Figure 8.5.8. The spinal cord is enclosed within, but is shorter than, the vertebral column.\r\n\r\n[caption id=\"attachment_3099\" align=\"alignnone\" width=\"482\"] Figure 8.5.8 The spinal cord (yellow) runs from the bottom of the brain to the lower back.<\/em>[\/caption]\r\nStructure of the Spinal Cord<\/h2>\r\nThe center of the spinal cord consists of gray matter, which is made up mainly of cell bodies of neurons, including interneurons and motor neurons. The gray matter is surrounded by white matter that consists mainly of myelinated axons of motor and sensory neurons. Spinal nerves, which connect the spinal cord to the PNS, exit from the spinal cord between vertebrae (see Figure 8.5.9).\r\n\r\n \r\n\r\n\r\n[caption id=\"attachment_3100\" align=\"alignleft\" width=\"291\"] Figure 8.5.9 This model shows three vertebrae (white) with branching spinal nerves (yellow) emerging from the either side of the spinal cord between vertebrae.<\/em>[\/caption]\r\n\r\n<\/div>\r\nFunctions of the Spinal Cord<\/h2>\r\nThe spinal cord serves as an information superhighway. It passes messages from the body to the brain and from the brain to the body. Sensory (afferent) nerves carry\u00a0nerve impulses\u00a0to the brain from sensory receptor\u00a0cells\u00a0everywhere in and on the body. Motor (efferent) nerves carry nerve impulses away from the brain to glands, organs, or\u00a0muscles throughout the body.\r\n\r\nThe spinal cord also independently controls certain rapid responses called\u00a0reflexes<\/strong> without any input from the brain. You can see how this may happen in Figure 8.5.10. A sensory receptor responds to a sensation and sends a nerve impulse along a sensory nerve to the spinal cord. In the spinal cord, the message passes to an interneuron and from the interneuron to a motor nerve, which carries the impulse to a muscle. The muscle contracts in response. These neuron connections form a reflex arc, which requires no input from the brain. No doubt you have experienced such reflex actions yourself. For example, you may have reached out to touch a pot on the stove, not realizing that it was very hot. Virtually at the same moment that you feel the burning heat, you jerk your arm back and remove your hand from the pot.\r\n\r\n \r\n\r\n\r\n[caption id=\"attachment_3101\" align=\"alignnone\" width=\"1038\"] Figure 8.5.10 This diagram shows what happens in a long reflex (top), in which sensory nerves carry the message all the way to the spinal cord; and in a short reflex (bottom), in which sensory nerves travel only to a ganglion outside the spinal cord. Note that interneurons are involved in reflexes, connecting sensory and motor neurons, but they are not actually shown in the diagram.<\/em>[\/caption]\r\n\r\n<\/div>\r\nInjuries to the Spinal Cord<\/h2>\r\nPhysical damage to the spinal cord may result in\u00a0[pb_glossary id=\"3102\"]paralysis[\/pb_glossary],<\/strong> which is loss of sensation and movement in part of the body. Paralysis generally affects all the areas of the body below the level of the injury, because nerve impulses are interrupted and can no longer travel back and forth between the brain and body beyond that point. If an injury to the spinal cord produces nothing more than swelling, the symptoms may be transient. However, if nerve fibres (axons) in the spinal cord are badly damaged, the loss of function may be permanent. Experimental studies have shown that spinal nerve fibres attempt to regrow, but tissue destruction usually produces scar tissue that cannot be penetrated by the regrowing nerves, as well other factors that inhibit nerve fibre regrowth in the central nervous system.\r\n\r\nFeature: My\u00a0Human Body<\/h1>\r\n<\/div>\r\nEach year, many millions of people have a stroke<\/a>, and stroke is the second leading cause of death in adults.\u00a0[pb_glossary id=\"3103\"]Stroke[\/pb_glossary],<\/strong>\u00a0also known as cerebrovascular accident, occurs when poor blood flow to the brain results in the death of brain cells. There are two main types of strokes:\r\n\r\n \t- Ischemic strokes occur due to lack of blood flow because of a blood clot in an artery going to the brain.<\/li>\r\n \t
- Hemorrhagic strokes occur due to bleeding from a broken blood vessel in the brain.<\/li>\r\n<\/ul>\r\nEither type of stroke may result in paralysis, loss of the ability to speak or comprehend speech, loss of bladder control, personality changes, and many other potential effects, depending on the part of the brain that is injured. The effects of a stroke may be mild and transient or more severe and permanent. A stroke may even be fatal. It generally depends on the type of stroke and how extensive it is.\r\n\r\nAre you at risk of a stroke? The main risk factor for stroke is age \u2014 about two-thirds of strokes occur in people over the age of 65. There is nothing you can do about your age, but most other stroke risk factors can be reduced with lifestyle changes or medications. The risk factors include high blood pressure, tobacco smoking, obesity, high blood cholesterol, diabetes mellitus, and atrial fibrillation.\r\n\r\nChances are good that you or someone you know is at risk of a stroke, so it is important to recognize a stroke if one occurs. A stroke is a medical emergency, and the more quickly treatment is given, the better the outcome is likely to be. In the case of ischemic strokes, the use of clot-busting drugs may prevent permanent brain damage if administered within three or four hours of the stroke. Remembering the signs of a stroke is easy. They are summed up by the acronym FAST.\r\n\r\n
\r\n8.5 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- The [pb_glossary id=\"5933\"]central nervous system[\/pb_glossary] is the part of the nervous system that includes the [pb_glossary id=\"5915\"]brain[\/pb_glossary] and [pb_glossary id=\"3010\"]spinal cord[\/pb_glossary]. It is physically protected by\u00a0bones, meninges, and [pb_glossary id=\"5939\"]cerebrospinal fluid[\/pb_glossary]. It is chemically protected by the blood-brain barrier.<\/li>\r\n \t
- The brain is the control center of the nervous system and of the entire organism. The brain uses a relatively large proportion of the body\u2019s\u00a0energy, primarily in the form of glucose.<\/li>\r\n \t
- The brain is divided into three major parts, each with different functions: the hindbrain, the midbrain and the forebrain.<\/li>\r\n \t
- Hindbrain consists of the medulla oblongata, the pons and the cerebellum, each of which perform specific functions.<\/li>\r\n \t
- The midbrain is primarily responsible for motor movement and in auditory and visual processing.<\/li>\r\n \t
- The forebrain contains many structures including:\r\n
\r\n \t- The cerebrum, which is further divided into left and right hemispheres. Each hemisphere has four lobes: frontal, parietal, temporal, and occipital. Each lobe is associated with specific senses or other functions.<\/li>\r\n \t
- The cerebrum\u00a0has a\u00a0thin outer layer called the cerebral cortex. Its many folds give it a large surface area. This is where most information processing takes place.<\/li>\r\n \t
- Inner structures of the brain include the hypothalamus \u2014 which controls the\u00a0endocrine system\u00a0via the\u00a0pituitary gland\u00a0\u2014 and the thalamus, which has several involuntary functions.<\/li>\r\n \t
- The hippocampus and amygdala, which are part of the limbic system and play important roles in memory, learning and emotions.<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t
- The spinal cord is a tubular bundle of nervous tissues that extends from the head down the middle of the back to the pelvis. It functions mainly to connect the brain with the\u00a0peripheral nervous system. It also controls certain rapid responses called reflexes without any input from the brain.<\/li>\r\n \t
- A spinal cord injury may lead to paralysis (loss of sensation and movement) of the body below the level of the injury, because nerve impulses can no longer travel up and down the spinal cord beyond that point.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n8.5 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- What is the central nervous system?<\/li>\r\n \t
- How is the central nervous system protected?<\/li>\r\n \t
- What is the overall function of the brain?<\/li>\r\n \t
- Identify the three main parts of the brain and one function of each part.<\/li>\r\n \t
- Describe the hemispheres of the brain.<\/li>\r\n \t
- Explain and give examples of lateralization of the brain.<\/li>\r\n \t
- Identify one function of each of the four lobes of the cerebrum.<\/li>\r\n \t
- [h5p id=\"562\"]<\/li>\r\n \t
- [h5p id=\"563\"]<\/li>\r\n \t
- Summarize the structure and function of the cerebral cortex. Explain how the hypothalamus controls the endocrine system.<\/li>\r\n \t
- Describe the spinal cord.<\/li>\r\n \t
- What is the main function of the spinal cord?<\/li>\r\n \t
- Explain how reflex actions occur.<\/li>\r\n \t
- Why do severe spinal cord injuries usually cause paralysis?<\/li>\r\n \t
- What do you think are some possible consequences of severe damage to the brain stem? How might this compare to the consequences of severe damage to the frontal lobe? Explain your answer.<\/li>\r\n \t
- Information travels very quickly in the nervous system, but generally, the longer the path between areas, the longer it takes. Based on this, explain why you think reflexes often occur at the spinal cord level, and do not require input from the brain.<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
\r\n8.5 Explore More<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=sewhbmh0ECg\r\nWhat if we could look inside human brains? - Moran Cerf, TED-Ed, 2013.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=ZMSbDwpIyF4\r\n
The left brain vs. right brain myth - Elizabeth Waters, TED-Ed, 2017.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?time_continue=1&v=aCv4K5aStdU&feature=emb_logo\r\n
Split-brain patient 'Joe' being tested with stimuli presented in different visual fields,\r\nmarkmcdermott, 2010.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n
Attributes<\/h2>\r\nFigure 8.5.1<\/strong>\r\n\r\nSensory_Homunculus-en.svg<\/a> by Popadius<\/a> on Wikimedia Commons is used under a CC BY 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0\/deed.en) license. (This is a derivative work from File:1421 Sensory Homunculus<\/a>.jpg by OpenStax College<\/a>)\r\n\r\nFigure 8.5.2<\/strong>\r\n\r\nOverview_of_Nervous_System<\/a>\u00a0by OpenStax<\/a> on Wikimedia Commons is used under a CC BY 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en) license.\r\n\r\nFigure 8.5.3<\/strong>\r\n\r\nDiagram_showing_the_brain_stem_which_includes_the_medulla_oblongata,_the_pons_and_the_midbrain_(2)_CRUK_294.svg<\/a> by Cancer Research UK<\/a> on Wikimedia Commons is used under a CC BY-SA 4.0 <\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\nFigure 8.5.4<\/strong>\r\n\r\nBrain_bulbar_region.svg<\/a> by Fvasconcellos<\/a> on Wikimedia Commons is used under a CC BY 2.5<\/a> license (derivative work from Brain human sagittal section.svg<\/a>\u00a0 by Patrick J. Lynch; Brain bulbar region.PNG<\/a> by DO11.10<\/a>).\r\n\r\nFigure 8.5.5<\/strong>\r\n\r\nMidbrain<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY 3.0 <\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0) license.\r\n\r\nFigure 8.5.6<\/strong>\r\n\r\nBrainLobes<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY 3.0 <\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0) license.\u00a0<\/span>\r\n\r\nFigure 8.5.7<\/strong>\r\n\r\nDiencephalon<\/a> by OpenStax<\/a> Wikimedia Commons is used under a CC BY 4.0 <\/a>(https:\/\/creativecommons.org\/licenses\/by\/4.0) license.\r\n\r\nFigure 8.5.8<\/strong>\r\n\r\nSpinalCord<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY 3.0 <\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0) license.\u00a0<\/span>\r\n\r\nFigure 8.5.9<\/strong>\r\n\r\nSpinal_readjustment_3<\/a> by Tomwsulcer<\/a> on\u00a0 Wikimedia Commons is used under a CC0 1.0<\/a> Universal Public Domain Dedication license (https:\/\/creativecommons.org\/publicdomain\/zero\/1.0\/deed.en).\r\n\r\nFigure 8.5.10<\/strong>\r\n\r\n1507_Short_and_Long_Reflexes<\/a> by OpenStax<\/a> on Wikimedia Commons is used under a CC BY 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en) license.\r\nReferences<\/h2>\r\n
Betts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2013, 28 May). Figure 14.23<\/span>\u00a0<\/span>The sensory homunculus <\/span>[digital image]. In Anatomy and Physiology<\/em> (Section 14.2). OpenStax. https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/14-2-central-processing\r\n<\/span><\/span><\/p>\r\nBetts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2013, 28 May). Figure 15.8 Short and long reflexes [digital image]. In Anatomy and Physiology<\/em> (Section 15.2). OpenStax. https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/15-2-autonomic-reflexes-and-homeostasis<\/p>\r\nBetts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2016, May 18). <\/span><\/span>Figure 12.2 Central and peripheral nervous system [digital image]. In Anatomy and Physiology<\/em> (Section 12.1). https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/12-1-basic-structure-and-function-of-the-nervous-system<\/span><\/span><\/p>\r\nBetts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2016, May 18). Figure 13.11 The diencephalon [digital image]. In Anatomy and Physiology<\/em> (Section 13.2). https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/13-2-the-central-nervous-system<\/p>\r\nBlausen.com staff. (2014). Medical gallery of Blausen Medical 2014. WikiJournal of Medicine,<\/em> 1<\/em> (2). DOI:10.15347\/wjm\/2014.010. ISSN 2002-4436<\/span><\/p>\r\nmarkmcdermott. (2010). Split-brain patient 'Joe' being tested with stimuli presented in different visual fields. YouTube. https:\/\/www.youtube.com\/user\/markmcdermott\/search?query=split<\/p>\r\n
Mayo Clinic Staff. (n.d.). Stroke [online article]. MayoClinic.org. https:\/\/www.mayoclinic.org\/diseases-conditions\/stroke\/symptoms-causes\/syc-20350113<\/p>\r\n
Soton Brain Hub. (2016, July 29). The limbic system. YouTube. https:\/\/www.youtube.com\/watch?v=jcrWPo_s6EE&feature=youtu.be<\/p>\r\n
TED-Ed. (2013, January 31). What if we could look inside human brains? - Moran Cerf. YouTube. https:\/\/www.youtube.com\/watch?v=sewhbmh0ECg&feature=youtu.be<\/p>\r\n
TED-Ed. (2017, July 24). The left brain vs. right brain myth - Elizabeth Waters. YouTube. https:\/\/www.youtube.com\/watch?v=ZMSbDwpIyF4&feature=youtu.be<\/p>\r\n ","rendered":"
<\/p>\nFigure 8.5.1 This picture is called an <\/em>homunculus.\u00a0<\/em><\/figcaption><\/figure>\nHomunculus<\/h1>\n
The very odd-looking drawing in Figure 8.5.1 is called a homunculus. The beige mass represents a cross-sectional wedge of the human brain, and the drawing shows some areas of the brain associated with different parts of the body. As you can see, larger areas of the brain in this region are associated with the hands, face, and tongue, as compared to the areas associated with the legs and feet. Given the importance of speech, manual dexterity, and face-to-face social interactions in human beings, it is not surprising that relatively large areas of the brain are needed to control these body parts. The brain is the most complex organ in the human body and part of the central nervous system.<\/p>\n
\nWhat Is the Central Nervous System?<\/h1>\n<\/div>\n
The central nervous system<\/a> (CNS) is the part of the nervous system that includes the brain<\/a> and spinal cord<\/a>. The drawing below (Figure 8.5.2) shows the central nervous system as one of two main divisions of the total nervous system. The other main division is the peripheral nervous system<\/a> (PNS). The CNS and PNS work together to control virtually all body functions.<\/p>\nFigure 8.5.2 The two main divisions of the nervous system: the central nervous system (CNS) \u2014 which includes the brain and spinal cord \u2014 and the peripheral nervous system (PNS), which includes nerves and ganglia (singular, ganglion), which transmit information between the CNS to the rest of the body.<\/em><\/figcaption><\/figure>\nThe delicate nervous tissues of the central nervous system are protected by major physical and chemical barriers. Physically, the brain and spinal cord are surrounded by tough meninges<\/a>, a three-layer protective sheath that also contains cushioning cerebrospinal fluid<\/a>. The\u00a0bones\u00a0of the skull and spinal vertebrae also contribute to physically protecting the brain and spinal cord. Chemically, the brain and spinal cord are isolated from the circulation\u00a0\u2014\u00a0and most toxins or pathogens in the\u00a0blood\u00a0\u2014\u00a0by the\u00a0blood-brain barrier<\/a>.<\/strong>\u00a0The blood-brain barrier is a highly selective membrane formed of endothelial\u00a0cells\u00a0that separates the circulating\u00a0blood\u00a0from extracellular fluid in the CNS. The barrier allows\u00a0water, certain gases, glucose, and some other molecules needed by the brain and spinal cord to cross from the blood into the CNS, while keeping out potentially harmful substances. These physical and chemical barriers make the CNS less susceptible to injury than the PNS. However, damage to the CNS is likely to have more serious consequences.<\/p>\n\nThe Brain<\/h1>\n<\/div>\n
The\u00a0brain<\/a><\/strong> is the control center of not only the rest of the nervous system, but of the entire organism. The adult brain makes up only about 2% of the body\u2019s weight, but it uses about 20% of the body\u2019s total energy. The brain contains an estimated 100 billion neurons, and each neuron<\/a> has thousands of synaptic connections to other neurons. The brain also has about the same number of neuroglia<\/a> as neurons. No wonder the brain uses so much energy! In addition, the brain uses mostly glucose<\/a> for energy. As a result, if the brain is deprived of glucose, it can lead to unconsciousness. The brain is able to store some glucose in the form of glycogen, but in much smaller amounts than are found in the liver and skeletal muscles.<\/p>\nThe brain controls such mental processes as reasoning, imagination, memory, and language. It also interprets information from the senses and commands the body to respond appropriately. It controls basic physical processes (such as breathing and heartbeat), as well as voluntary activities (such as walking and writing). The brain has three major regions: the hindbrain, the midbrain and the forebrain. These parts are shown in Figure 8.5.3 and described below.<\/p>\nFigure 8.5.3 Diagram of the forebrain, midbrain and hindbrain. <\/em><\/figcaption><\/figure>\n\n <\/p>\n<\/div>\n
The Hindbrain<\/h2>\nFigure 8.5.4 The hindbrain consists of the cerebellum,<\/em> medulla oblongata, and the pons. It plays the extremely important role of connecting the brain to the rest of the body via the spinal cord.<\/em><\/figcaption><\/figure>\nThe\u00a0hindbrain<\/a>, <\/strong>which includes the cerebellum<\/a>, medulla oblongata<\/a>, and the pons<\/a>. The hindbrain is the lowest part of the brain. It resembles a stalk and platform on which the cerebrum is perched. The components of the hindbrain connect the rest of the brain with the spinal cord and passes nerve impulses between the brain and spinal cord.<\/p>\nCerebellum<\/h3>\n
The\u00a0cerebellum<\/a><\/strong> is located just below the cerebrum and at the back of the brain behind the brain stem. It coordinates your voluntary movements, balance, and posture.\u00a0 Information from your inner ear, joints and muscles, and eyes are all knitted together in the cerebellum so that you have awareness of where you are in 3-dimensional space.\u00a0 Patients who have suffered damage to their cerebellum may suffer from balance disorder. In addition the cerebellum plays a major role in motor learning (like how to ride a bike or how to do a backflip on a trampoline) through trial and error.\u00a0 While traditionally, the cerebellum was thought to only be involved in motor functions, we now know that it also plays an important role in memory and learning.<\/p>\nMedulla Oblongata<\/h3>\n
The\u00a0medulla oblongata<\/a><\/strong> makes up part of the brainstem and sits in front of and just below the cerebellum, at the very top of the spinal cord.\u00a0 It is responsible for control of heart rate, respiration rate and blood pressure, as well as reflexes such as vomiting, coughing, sneezing and swallowing.<\/p>\nPons<\/h3>\n
The\u00a0pons<\/a><\/strong> is located in front of the cerebellum and above the medulla oblongata.\u00a0 It has several functions, including receiving sensory information from the face, regulating rate and depth of breaths, as well as sleep cycles.<\/p>\nMidbrain<\/h2>\nFigure 8.5.5 The brainstem includes the midbrain, the pons and the medulla oblongata.<\/em><\/figcaption><\/figure>\nThe midbrain is the topmost part of the brainstem and is the essential connection between and brain and spinal cord.\u00a0 The three main parts of the midbrain are the colliculi, the tegmentum, and the cerebral peduncles.\u00a0 These structures are all considered part of the brainstem, which consists of the medulla oblongata, the pons and the midbrain.<\/p>\n
Reticular Activating System<\/h3>\n
The reticular activating system<\/a> (RAS) is responsible for the sleep-wake cycle and wakefulness.\u00a0 It also regulates attention, ability to focus and arousal.<\/p>\nForebrain<\/h2>\n
The forebrain is the anterior (forwardmost) part of the brain and includes the cerebrum, the thalamus and hypothalamus, hippocampus, amygdala, and limbic system.\u00a0 This portion of the brain is responsible for processing incoming sensory information, performing complex cognitive activities (speech, abstract thought, etc) and governing voluntary motor movements.\u00a0 \u00a0The forebrain also controls body temperature, reproductive functions, eating, sleeping and the display of emotions.<\/p>\n
Cerebrum<\/h3>\n
The\u00a0cerebrum<\/a><\/strong>\u00a0is the largest part of the brain. It controls conscious, intellectual functions.\u00a0Among other things,\u00a0it controls reasoning, language, memory, sight, touch, and hearing. When you read a book, play a video game, or recognize a classmate, you are using your cerebrum.<\/p>\nHemispheres and Lateralization of the Cerebrum<\/h4>\n
The cerebrum is divided from front to back into two halves called the left and right\u00a0hemispheres<\/a>.<\/strong>\u00a0The two hemispheres are connected by a thick bundle of axons, known as the corpus callosum<\/a>, which lies deep within the brain. The corpus callosum is the main avenue of\u00a0communication between the two hemispheres. It connects each point in the cerebrum to the mirror-image point in the opposite hemisphere.<\/p>\nThe right and left hemispheres of the cerebrum are similar in shape, and most areas of cerebrum are found in both hemispheres. Some areas, however, show\u00a0lateralization<\/a>,<\/strong>\u00a0or a\u00a0concentration\u00a0in one hemisphere or the other.\u00a0In most people, for example, language functions are more concentrated in the left hemisphere, whereas abstract reasoning and visual-spatial abilities are more concentrated in the right hemisphere.<\/p>\nFor reasons that are not yet clear, each hemisphere of the brain interacts primarily with the opposite side of the body. The left side of the brain receives messages from and sends commands to the right side of the body, and the right side of the brain\u00a0receives messages from and sends commands to the left side of the body. Sensory nerves from the spinal cord to the brain and motor nerves from the brain to the spinal cord both cross the midline of the body at the level of the brain stem.<\/p>\n
Lobes of the Cerebrum<\/h4>\n
Each hemisphere<\/a> of the cerebrum is further divided into the four lobes shown in Figure 8.5.6 and described below.<\/p>\nFigure 8.5.6 The cerebrum is organized into four lobes: frontal, parietal, occipital, and temporal.<\/em><\/figcaption><\/figure>\n\nEach hemisphere of the cerebrum consists of four parts, called lobes. Each lobe is associated with particular brain functions. Just one function of each lobe is listed here.<\/p>\n<\/div>\n
\n- The\u00a0frontal lobes<\/a><\/strong>\u00a0are located at the front of the brain behind the forehead. The frontal lobes are associated with executive functions, such as attention, self-control, planning, problem solving, reasoning, abstract thought, language, and personality.<\/li>\n
- The\u00a0parietal lobes<\/a><\/strong>\u00a0are located behind the frontal lobes at the top of the head. The parietal lobes are involved in sensation \u2014 including\u00a0temperature, touch, and taste. Reading and arithmetic are also functions of the parietal lobes.<\/li>\n
- The\u00a0temporal lobes<\/a><\/strong>\u00a0are located at the sides of the head below the frontal and parietal lobes. The temporal lobes enable hearing, the formation and retrieval of memories, and the integration of memories and sensations.<\/li>\n
- The\u00a0occipital lobes<\/a><\/strong>\u00a0are located at the back of the head below the parietal lobes. The occipital lobes are the smallest of the four pairs of lobes. They are dedicated almost solely to\u00a0vision.<\/li>\n<\/ul>\n
Cerebral Cortex<\/h4>\n
Most of the information processing in the brain actually takes place in the\u00a0cerebral cortex<\/a><\/strong>, a rind of gray matter and other tissues just a few millimetres thick that makes up the outer surface of the cerebrum in both hemispheres of the brain. The cerebral cortex has many folds in it, greatly increasing the amount of surface area of the brain that can fit within the skull. Because of all the folds in the human cerebral cortex, it has a surface area of about 2,500 cm2<\/sup>\u00a0(2.5 ft2<\/sup>). The size and importance of the cerebral cortex is far greater in the human brain than the brains of any other vertebrates, including nonhuman\u00a0primates.<\/p>\nThe Limbic System<\/h3>\n
The limbic system consists of the hypothalamus, thalamus, the hippocampus and amygdala. The structures and interacting areas of the\u00a0limbic system<\/a><\/b>\u00a0are involved in motivation, emotion, learning, and memory.<\/p>\nThalamus and Hypothalamus<\/h4>\n
Several structures are located deep within the brain and are important for communication between the brain and spinal cord (or the rest of the body). These structures include the hypothalamus and thalamus. The diagram below (Figure 8.5.7) shows where these structures are located in the brain. Like the two halves of the cerebrum, the hypothalamus and thalamus exist in two halves, one in each hemisphere.<\/p>\nFigure 8.5.7 Structures deep within the brain include the hypothalamus and thalamus.<\/em><\/figcaption><\/figure>\nThe\u00a0hypothalamus<\/a><\/strong>\u00a0is located just above the brain stem, and is about the size of an almond. The hypothalamus is responsible for certain metabolic processes and other activities of the autonomic nervous system<\/a>, including body\u00a0temperature,\u00a0heart\u00a0rate, hunger, thirst, fatigue, sleep, wakefulness, and circadian (24-hour) rhythms. The hypothalamus is also an important emotional center of the brain. The hypothalamus can regulate so many body functions because it responds to many different internal and external signals, including messages from the brain, light, steroid hormones, stress, and invading pathogens, among others.<\/p>\nOne way the hypothalamus influences body functions is by synthesizing hormones that directly influence body processes. It synthesizes the hormone oxytocin<\/a>, which stimulates uterine contractions during childbirth and the letdown of milk during lactation. It also synthesizes antidiuretic hormone<\/a>, which stimulates the kidneys to reabsorb more water and excrete more concentrated urine. These two hormones are sent from the hypothalamus via a stalk-like structure called the infundibulum (see Figure 8.5.7) directly to the posterior (back) portion of the pituitary gland, which secretes them into the blood.<\/p>\nThe main way the hypothalamus influences body functions is by controlling the\u00a0pituitary gland<\/a>, known as the master gland of the\u00a0endocrine system. The hypothalamus synthesizes neurohormones called releasing factors that travel through the infundibulum directly to the anterior (front) part of the pituitary gland. The releasing factors generally either stimulate or inhibit the secretion of anterior pituitary hormones, most of which control other glands of the endocrine system.<\/p>\n
Hemispheres and Lateralization of the Cerebrum<\/h4>\r\nThe cerebrum is divided from front to back into two halves called the left and right\u00a0[pb_glossary id=\"3083\"]hemispheres[\/pb_glossary].<\/strong>\u00a0The two hemispheres are connected by a thick bundle of axons, known as the [pb_glossary id=\"5955\"]corpus callosum[\/pb_glossary], which lies deep within the brain. The corpus callosum is the main avenue of\u00a0communication between the two hemispheres. It connects each point in the cerebrum to the mirror-image point in the opposite hemisphere.\r\n\r\nThe right and left hemispheres of the cerebrum are similar in shape, and most areas of cerebrum are found in both hemispheres. Some areas, however, show\u00a0[pb_glossary id=\"3085\"]lateralization[\/pb_glossary],<\/strong>\u00a0or a\u00a0concentration\u00a0in one hemisphere or the other.\u00a0In most people, for example, language functions are more concentrated in the left hemisphere, whereas abstract reasoning and visual-spatial abilities are more concentrated in the right hemisphere.\r\n\r\nFor reasons that are not yet clear, each hemisphere of the brain interacts primarily with the opposite side of the body. The left side of the brain receives messages from and sends commands to the right side of the body, and the right side of the brain\u00a0receives messages from and sends commands to the left side of the body. Sensory nerves from the spinal cord to the brain and motor nerves from the brain to the spinal cord both cross the midline of the body at the level of the brain stem.\r\nLobes of the Cerebrum<\/h4>\r\nEach [pb_glossary id=\"3083\"]hemisphere[\/pb_glossary] of the cerebrum is further divided into the four lobes shown in Figure 8.5.6 and described below.\r\n\r\n[caption id=\"attachment_3086\" align=\"aligncenter\" width=\"680\"] Figure 8.5.6 The cerebrum is organized into four lobes: frontal, parietal, occipital, and temporal.<\/em>[\/caption]\r\n\r\n\r\n\r\nEach hemisphere of the cerebrum consists of four parts, called lobes. Each lobe is associated with particular brain functions. Just one function of each lobe is listed here.\r\n\r\n<\/div>\r\n\r\n \t- The\u00a0[pb_glossary id=\"6021\"]frontal lobes[\/pb_glossary]<\/strong>\u00a0are located at the front of the brain behind the forehead. The frontal lobes are associated with executive functions, such as attention, self-control, planning, problem solving, reasoning, abstract thought, language, and personality.<\/li>\r\n \t
- The\u00a0[pb_glossary id=\"3088\"]parietal lobes[\/pb_glossary]<\/strong>\u00a0are located behind the frontal lobes at the top of the head. The parietal lobes are involved in sensation \u2014 including\u00a0temperature, touch, and taste. Reading and arithmetic are also functions of the parietal lobes.<\/li>\r\n \t
- The\u00a0[pb_glossary id=\"3089\"]temporal lobes[\/pb_glossary]<\/strong>\u00a0are located at the sides of the head below the frontal and parietal lobes. The temporal lobes enable hearing, the formation and retrieval of memories, and the integration of memories and sensations.<\/li>\r\n \t
- The\u00a0[pb_glossary id=\"3090\"]occipital lobes[\/pb_glossary]<\/strong>\u00a0are located at the back of the head below the parietal lobes. The occipital lobes are the smallest of the four pairs of lobes. They are dedicated almost solely to\u00a0vision.<\/li>\r\n<\/ul>\r\n
Cerebral Cortex<\/h4>\r\nMost of the information processing in the brain actually takes place in the\u00a0[pb_glossary id=\"5937\"]cerebral cortex[\/pb_glossary]<\/strong>, a rind of gray matter and other tissues just a few millimetres thick that makes up the outer surface of the cerebrum in both hemispheres of the brain. The cerebral cortex has many folds in it, greatly increasing the amount of surface area of the brain that can fit within the skull. Because of all the folds in the human cerebral cortex, it has a surface area of about 2,500 cm2<\/sup>\u00a0(2.5 ft2<\/sup>). The size and importance of the cerebral cortex is far greater in the human brain than the brains of any other vertebrates, including nonhuman\u00a0primates.\r\nThe Limbic System<\/h3>\r\nThe limbic system consists of the hypothalamus, thalamus, the hippocampus and amygdala. The structures and interacting areas of the\u00a0[pb_glossary id=\"3098\"]limbic system[\/pb_glossary]<\/b>\u00a0are involved in motivation, emotion, learning, and memory.\r\nThalamus and Hypothalamus<\/h4>\r\nSeveral structures are located deep within the brain and are important for communication between the brain and spinal cord (or the rest of the body). These structures include the hypothalamus and thalamus. The diagram below (Figure 8.5.7) shows where these structures are located in the brain. Like the two halves of the cerebrum, the hypothalamus and thalamus exist in two halves, one in each hemisphere.\r\n\r\n[caption id=\"attachment_3092\" align=\"alignleft\" width=\"363\"] Figure 8.5.7 Structures deep within the brain include the hypothalamus and thalamus.<\/em>[\/caption]\r\n\r\nThe\u00a0[pb_glossary id=\"2937\"]hypothalamus[\/pb_glossary]<\/strong>\u00a0is located just above the brain stem, and is about the size of an almond. The hypothalamus is responsible for certain metabolic processes and other activities of the [pb_glossary id=\"5899\"]autonomic nervous system[\/pb_glossary], including body\u00a0temperature,\u00a0heart\u00a0rate, hunger, thirst, fatigue, sleep, wakefulness, and circadian (24-hour) rhythms. The hypothalamus is also an important emotional center of the brain. The hypothalamus can regulate so many body functions because it responds to many different internal and external signals, including messages from the brain, light, steroid hormones, stress, and invading pathogens, among others.\r\n\r\nOne way the hypothalamus influences body functions is by synthesizing hormones that directly influence body processes. It synthesizes the hormone [pb_glossary id=\"3093\"]oxytocin[\/pb_glossary], which stimulates uterine contractions during childbirth and the letdown of milk during lactation. It also synthesizes [pb_glossary id=\"5893\"]antidiuretic hormone[\/pb_glossary], which stimulates the kidneys to reabsorb more water and excrete more concentrated urine. These two hormones are sent from the hypothalamus via a stalk-like structure called the infundibulum (see Figure 8.5.7) directly to the posterior (back) portion of the pituitary gland, which secretes them into the blood.\r\n\r\nThe main way the hypothalamus influences body functions is by controlling the\u00a0[pb_glossary id=\"2938\"]pituitary gland[\/pb_glossary], known as the master gland of the\u00a0endocrine system. The hypothalamus synthesizes neurohormones called releasing factors that travel through the infundibulum directly to the anterior (front) part of the pituitary gland. The releasing factors generally either stimulate or inhibit the secretion of anterior pituitary hormones, most of which control other glands of the endocrine system.\r\n\r\nThe\u00a0[pb_glossary id=\"3095\"]thalamus[\/pb_glossary],<\/strong> which is located near the hypothalamus (see Figure 8.5.7), is a major hub for information traveling back and forth between the spinal cord and cerebrum. It relays sensory signals to the cerebral cortex and motor signals to the spinal cord. It is also involved in the regulation of consciousness, sleep, and alertness.\r\n\r\nHippocampus and Amygdala<\/h4>\r\nThe [pb_glossary id=\"3096\"]hippocampus[\/pb_glossary] is a complex structure embedded deep in the temporal lobe.\u00a0 It plays a major role in learning and memory and contributes to regulation of motivation and emotion. The amygdala is the part of the brain responsible for formation and storage of memories associated with emotional events.\r\n\r\nWatch \"The Limbic System\" by Soton Brain Hub to learn about the location and functions of the limbic system.\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=jcrWPo_s6EE\r\n
The Limbic System, Soton Brain Hub, 2016.<\/p>\r\n\r\n
Spinal Cord<\/h1>\r\n<\/div>\r\nThe\u00a0[pb_glossary id=\"3010\"]spinal cord[\/pb_glossary]<\/strong> is a long, thin, tubular bundle of nervous tissues that extends from the brain stem and continues down the center of the back to the pelvis. It is highlighted in yellow in Figure 8.5.8. The spinal cord is enclosed within, but is shorter than, the vertebral column.\r\n\r\n[caption id=\"attachment_3099\" align=\"alignnone\" width=\"482\"] Figure 8.5.8 The spinal cord (yellow) runs from the bottom of the brain to the lower back.<\/em>[\/caption]\r\nStructure of the Spinal Cord<\/h2>\r\nThe center of the spinal cord consists of gray matter, which is made up mainly of cell bodies of neurons, including interneurons and motor neurons. The gray matter is surrounded by white matter that consists mainly of myelinated axons of motor and sensory neurons. Spinal nerves, which connect the spinal cord to the PNS, exit from the spinal cord between vertebrae (see Figure 8.5.9).\r\n\r\n \r\n\r\n\r\n[caption id=\"attachment_3100\" align=\"alignleft\" width=\"291\"] Figure 8.5.9 This model shows three vertebrae (white) with branching spinal nerves (yellow) emerging from the either side of the spinal cord between vertebrae.<\/em>[\/caption]\r\n\r\n<\/div>\r\nFunctions of the Spinal Cord<\/h2>\r\nThe spinal cord serves as an information superhighway. It passes messages from the body to the brain and from the brain to the body. Sensory (afferent) nerves carry\u00a0nerve impulses\u00a0to the brain from sensory receptor\u00a0cells\u00a0everywhere in and on the body. Motor (efferent) nerves carry nerve impulses away from the brain to glands, organs, or\u00a0muscles throughout the body.\r\n\r\nThe spinal cord also independently controls certain rapid responses called\u00a0reflexes<\/strong> without any input from the brain. You can see how this may happen in Figure 8.5.10. A sensory receptor responds to a sensation and sends a nerve impulse along a sensory nerve to the spinal cord. In the spinal cord, the message passes to an interneuron and from the interneuron to a motor nerve, which carries the impulse to a muscle. The muscle contracts in response. These neuron connections form a reflex arc, which requires no input from the brain. No doubt you have experienced such reflex actions yourself. For example, you may have reached out to touch a pot on the stove, not realizing that it was very hot. Virtually at the same moment that you feel the burning heat, you jerk your arm back and remove your hand from the pot.\r\n\r\n \r\n\r\n\r\n[caption id=\"attachment_3101\" align=\"alignnone\" width=\"1038\"] Figure 8.5.10 This diagram shows what happens in a long reflex (top), in which sensory nerves carry the message all the way to the spinal cord; and in a short reflex (bottom), in which sensory nerves travel only to a ganglion outside the spinal cord. Note that interneurons are involved in reflexes, connecting sensory and motor neurons, but they are not actually shown in the diagram.<\/em>[\/caption]\r\n\r\n<\/div>\r\nInjuries to the Spinal Cord<\/h2>\r\nPhysical damage to the spinal cord may result in\u00a0[pb_glossary id=\"3102\"]paralysis[\/pb_glossary],<\/strong> which is loss of sensation and movement in part of the body. Paralysis generally affects all the areas of the body below the level of the injury, because nerve impulses are interrupted and can no longer travel back and forth between the brain and body beyond that point. If an injury to the spinal cord produces nothing more than swelling, the symptoms may be transient. However, if nerve fibres (axons) in the spinal cord are badly damaged, the loss of function may be permanent. Experimental studies have shown that spinal nerve fibres attempt to regrow, but tissue destruction usually produces scar tissue that cannot be penetrated by the regrowing nerves, as well other factors that inhibit nerve fibre regrowth in the central nervous system.\r\n\r\nFeature: My\u00a0Human Body<\/h1>\r\n<\/div>\r\nEach year, many millions of people have a stroke<\/a>, and stroke is the second leading cause of death in adults.\u00a0[pb_glossary id=\"3103\"]Stroke[\/pb_glossary],<\/strong>\u00a0also known as cerebrovascular accident, occurs when poor blood flow to the brain results in the death of brain cells. There are two main types of strokes:\r\n\r\n \t- Ischemic strokes occur due to lack of blood flow because of a blood clot in an artery going to the brain.<\/li>\r\n \t
- Hemorrhagic strokes occur due to bleeding from a broken blood vessel in the brain.<\/li>\r\n<\/ul>\r\nEither type of stroke may result in paralysis, loss of the ability to speak or comprehend speech, loss of bladder control, personality changes, and many other potential effects, depending on the part of the brain that is injured. The effects of a stroke may be mild and transient or more severe and permanent. A stroke may even be fatal. It generally depends on the type of stroke and how extensive it is.\r\n\r\nAre you at risk of a stroke? The main risk factor for stroke is age \u2014 about two-thirds of strokes occur in people over the age of 65. There is nothing you can do about your age, but most other stroke risk factors can be reduced with lifestyle changes or medications. The risk factors include high blood pressure, tobacco smoking, obesity, high blood cholesterol, diabetes mellitus, and atrial fibrillation.\r\n\r\nChances are good that you or someone you know is at risk of a stroke, so it is important to recognize a stroke if one occurs. A stroke is a medical emergency, and the more quickly treatment is given, the better the outcome is likely to be. In the case of ischemic strokes, the use of clot-busting drugs may prevent permanent brain damage if administered within three or four hours of the stroke. Remembering the signs of a stroke is easy. They are summed up by the acronym FAST.\r\n\r\n
\r\n8.5 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- The [pb_glossary id=\"5933\"]central nervous system[\/pb_glossary] is the part of the nervous system that includes the [pb_glossary id=\"5915\"]brain[\/pb_glossary] and [pb_glossary id=\"3010\"]spinal cord[\/pb_glossary]. It is physically protected by\u00a0bones, meninges, and [pb_glossary id=\"5939\"]cerebrospinal fluid[\/pb_glossary]. It is chemically protected by the blood-brain barrier.<\/li>\r\n \t
- The brain is the control center of the nervous system and of the entire organism. The brain uses a relatively large proportion of the body\u2019s\u00a0energy, primarily in the form of glucose.<\/li>\r\n \t
- The brain is divided into three major parts, each with different functions: the hindbrain, the midbrain and the forebrain.<\/li>\r\n \t
- Hindbrain consists of the medulla oblongata, the pons and the cerebellum, each of which perform specific functions.<\/li>\r\n \t
- The midbrain is primarily responsible for motor movement and in auditory and visual processing.<\/li>\r\n \t
- The forebrain contains many structures including:\r\n
\r\n \t- The cerebrum, which is further divided into left and right hemispheres. Each hemisphere has four lobes: frontal, parietal, temporal, and occipital. Each lobe is associated with specific senses or other functions.<\/li>\r\n \t
- The cerebrum\u00a0has a\u00a0thin outer layer called the cerebral cortex. Its many folds give it a large surface area. This is where most information processing takes place.<\/li>\r\n \t
- Inner structures of the brain include the hypothalamus \u2014 which controls the\u00a0endocrine system\u00a0via the\u00a0pituitary gland\u00a0\u2014 and the thalamus, which has several involuntary functions.<\/li>\r\n \t
- The hippocampus and amygdala, which are part of the limbic system and play important roles in memory, learning and emotions.<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t
- The spinal cord is a tubular bundle of nervous tissues that extends from the head down the middle of the back to the pelvis. It functions mainly to connect the brain with the\u00a0peripheral nervous system. It also controls certain rapid responses called reflexes without any input from the brain.<\/li>\r\n \t
- A spinal cord injury may lead to paralysis (loss of sensation and movement) of the body below the level of the injury, because nerve impulses can no longer travel up and down the spinal cord beyond that point.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n8.5 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- What is the central nervous system?<\/li>\r\n \t
- How is the central nervous system protected?<\/li>\r\n \t
- What is the overall function of the brain?<\/li>\r\n \t
- Identify the three main parts of the brain and one function of each part.<\/li>\r\n \t
- Describe the hemispheres of the brain.<\/li>\r\n \t
- Explain and give examples of lateralization of the brain.<\/li>\r\n \t
- Identify one function of each of the four lobes of the cerebrum.<\/li>\r\n \t
- [h5p id=\"562\"]<\/li>\r\n \t
- [h5p id=\"563\"]<\/li>\r\n \t
- Summarize the structure and function of the cerebral cortex. Explain how the hypothalamus controls the endocrine system.<\/li>\r\n \t
- Describe the spinal cord.<\/li>\r\n \t
- What is the main function of the spinal cord?<\/li>\r\n \t
- Explain how reflex actions occur.<\/li>\r\n \t
- Why do severe spinal cord injuries usually cause paralysis?<\/li>\r\n \t
- What do you think are some possible consequences of severe damage to the brain stem? How might this compare to the consequences of severe damage to the frontal lobe? Explain your answer.<\/li>\r\n \t
- Information travels very quickly in the nervous system, but generally, the longer the path between areas, the longer it takes. Based on this, explain why you think reflexes often occur at the spinal cord level, and do not require input from the brain.<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
\r\n8.5 Explore More<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=sewhbmh0ECg\r\nWhat if we could look inside human brains? - Moran Cerf, TED-Ed, 2013.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=ZMSbDwpIyF4\r\n
The left brain vs. right brain myth - Elizabeth Waters, TED-Ed, 2017.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?time_continue=1&v=aCv4K5aStdU&feature=emb_logo\r\n
Split-brain patient 'Joe' being tested with stimuli presented in different visual fields,\r\nmarkmcdermott, 2010.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n
Attributes<\/h2>\r\nFigure 8.5.1<\/strong>\r\n\r\nSensory_Homunculus-en.svg<\/a> by Popadius<\/a> on Wikimedia Commons is used under a CC BY 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0\/deed.en) license. (This is a derivative work from File:1421 Sensory Homunculus<\/a>.jpg by OpenStax College<\/a>)\r\n\r\nFigure 8.5.2<\/strong>\r\n\r\nOverview_of_Nervous_System<\/a>\u00a0by OpenStax<\/a> on Wikimedia Commons is used under a CC BY 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en) license.\r\n\r\nFigure 8.5.3<\/strong>\r\n\r\nDiagram_showing_the_brain_stem_which_includes_the_medulla_oblongata,_the_pons_and_the_midbrain_(2)_CRUK_294.svg<\/a> by Cancer Research UK<\/a> on Wikimedia Commons is used under a CC BY-SA 4.0 <\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\nFigure 8.5.4<\/strong>\r\n\r\nBrain_bulbar_region.svg<\/a> by Fvasconcellos<\/a> on Wikimedia Commons is used under a CC BY 2.5<\/a> license (derivative work from Brain human sagittal section.svg<\/a>\u00a0 by Patrick J. Lynch; Brain bulbar region.PNG<\/a> by DO11.10<\/a>).\r\n\r\nFigure 8.5.5<\/strong>\r\n\r\nMidbrain<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY 3.0 <\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0) license.\r\n\r\nFigure 8.5.6<\/strong>\r\n\r\nBrainLobes<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY 3.0 <\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0) license.\u00a0<\/span>\r\n\r\nFigure 8.5.7<\/strong>\r\n\r\nDiencephalon<\/a> by OpenStax<\/a> Wikimedia Commons is used under a CC BY 4.0 <\/a>(https:\/\/creativecommons.org\/licenses\/by\/4.0) license.\r\n\r\nFigure 8.5.8<\/strong>\r\n\r\nSpinalCord<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY 3.0 <\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0) license.\u00a0<\/span>\r\n\r\nFigure 8.5.9<\/strong>\r\n\r\nSpinal_readjustment_3<\/a> by Tomwsulcer<\/a> on\u00a0 Wikimedia Commons is used under a CC0 1.0<\/a> Universal Public Domain Dedication license (https:\/\/creativecommons.org\/publicdomain\/zero\/1.0\/deed.en).\r\n\r\nFigure 8.5.10<\/strong>\r\n\r\n1507_Short_and_Long_Reflexes<\/a> by OpenStax<\/a> on Wikimedia Commons is used under a CC BY 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en) license.\r\nReferences<\/h2>\r\n
Betts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2013, 28 May). Figure 14.23<\/span>\u00a0<\/span>The sensory homunculus <\/span>[digital image]. In Anatomy and Physiology<\/em> (Section 14.2). OpenStax. https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/14-2-central-processing\r\n<\/span><\/span><\/p>\r\nBetts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2013, 28 May). Figure 15.8 Short and long reflexes [digital image]. In Anatomy and Physiology<\/em> (Section 15.2). OpenStax. https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/15-2-autonomic-reflexes-and-homeostasis<\/p>\r\nBetts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2016, May 18). <\/span><\/span>Figure 12.2 Central and peripheral nervous system [digital image]. In Anatomy and Physiology<\/em> (Section 12.1). https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/12-1-basic-structure-and-function-of-the-nervous-system<\/span><\/span><\/p>\r\nBetts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2016, May 18). Figure 13.11 The diencephalon [digital image]. In Anatomy and Physiology<\/em> (Section 13.2). https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/13-2-the-central-nervous-system<\/p>\r\nBlausen.com staff. (2014). Medical gallery of Blausen Medical 2014. WikiJournal of Medicine,<\/em> 1<\/em> (2). DOI:10.15347\/wjm\/2014.010. ISSN 2002-4436<\/span><\/p>\r\nmarkmcdermott. (2010). Split-brain patient 'Joe' being tested with stimuli presented in different visual fields. YouTube. https:\/\/www.youtube.com\/user\/markmcdermott\/search?query=split<\/p>\r\n
Mayo Clinic Staff. (n.d.). Stroke [online article]. MayoClinic.org. https:\/\/www.mayoclinic.org\/diseases-conditions\/stroke\/symptoms-causes\/syc-20350113<\/p>\r\n
Soton Brain Hub. (2016, July 29). The limbic system. YouTube. https:\/\/www.youtube.com\/watch?v=jcrWPo_s6EE&feature=youtu.be<\/p>\r\n
TED-Ed. (2013, January 31). What if we could look inside human brains? - Moran Cerf. YouTube. https:\/\/www.youtube.com\/watch?v=sewhbmh0ECg&feature=youtu.be<\/p>\r\n
TED-Ed. (2017, July 24). The left brain vs. right brain myth - Elizabeth Waters. YouTube. https:\/\/www.youtube.com\/watch?v=ZMSbDwpIyF4&feature=youtu.be<\/p>\r\n ","rendered":"
<\/p>\nFigure 8.5.1 This picture is called an <\/em>homunculus.\u00a0<\/em><\/figcaption><\/figure>\nHomunculus<\/h1>\n
The very odd-looking drawing in Figure 8.5.1 is called a homunculus. The beige mass represents a cross-sectional wedge of the human brain, and the drawing shows some areas of the brain associated with different parts of the body. As you can see, larger areas of the brain in this region are associated with the hands, face, and tongue, as compared to the areas associated with the legs and feet. Given the importance of speech, manual dexterity, and face-to-face social interactions in human beings, it is not surprising that relatively large areas of the brain are needed to control these body parts. The brain is the most complex organ in the human body and part of the central nervous system.<\/p>\n
\nWhat Is the Central Nervous System?<\/h1>\n<\/div>\n
The central nervous system<\/a> (CNS) is the part of the nervous system that includes the brain<\/a> and spinal cord<\/a>. The drawing below (Figure 8.5.2) shows the central nervous system as one of two main divisions of the total nervous system. The other main division is the peripheral nervous system<\/a> (PNS). The CNS and PNS work together to control virtually all body functions.<\/p>\nFigure 8.5.2 The two main divisions of the nervous system: the central nervous system (CNS) \u2014 which includes the brain and spinal cord \u2014 and the peripheral nervous system (PNS), which includes nerves and ganglia (singular, ganglion), which transmit information between the CNS to the rest of the body.<\/em><\/figcaption><\/figure>\nThe delicate nervous tissues of the central nervous system are protected by major physical and chemical barriers. Physically, the brain and spinal cord are surrounded by tough meninges<\/a>, a three-layer protective sheath that also contains cushioning cerebrospinal fluid<\/a>. The\u00a0bones\u00a0of the skull and spinal vertebrae also contribute to physically protecting the brain and spinal cord. Chemically, the brain and spinal cord are isolated from the circulation\u00a0\u2014\u00a0and most toxins or pathogens in the\u00a0blood\u00a0\u2014\u00a0by the\u00a0blood-brain barrier<\/a>.<\/strong>\u00a0The blood-brain barrier is a highly selective membrane formed of endothelial\u00a0cells\u00a0that separates the circulating\u00a0blood\u00a0from extracellular fluid in the CNS. The barrier allows\u00a0water, certain gases, glucose, and some other molecules needed by the brain and spinal cord to cross from the blood into the CNS, while keeping out potentially harmful substances. These physical and chemical barriers make the CNS less susceptible to injury than the PNS. However, damage to the CNS is likely to have more serious consequences.<\/p>\n\nThe Brain<\/h1>\n<\/div>\n
The\u00a0brain<\/a><\/strong> is the control center of not only the rest of the nervous system, but of the entire organism. The adult brain makes up only about 2% of the body\u2019s weight, but it uses about 20% of the body\u2019s total energy. The brain contains an estimated 100 billion neurons, and each neuron<\/a> has thousands of synaptic connections to other neurons. The brain also has about the same number of neuroglia<\/a> as neurons. No wonder the brain uses so much energy! In addition, the brain uses mostly glucose<\/a> for energy. As a result, if the brain is deprived of glucose, it can lead to unconsciousness. The brain is able to store some glucose in the form of glycogen, but in much smaller amounts than are found in the liver and skeletal muscles.<\/p>\nThe brain controls such mental processes as reasoning, imagination, memory, and language. It also interprets information from the senses and commands the body to respond appropriately. It controls basic physical processes (such as breathing and heartbeat), as well as voluntary activities (such as walking and writing). The brain has three major regions: the hindbrain, the midbrain and the forebrain. These parts are shown in Figure 8.5.3 and described below.<\/p>\nFigure 8.5.3 Diagram of the forebrain, midbrain and hindbrain. <\/em><\/figcaption><\/figure>\n\n <\/p>\n<\/div>\n
The Hindbrain<\/h2>\nFigure 8.5.4 The hindbrain consists of the cerebellum,<\/em> medulla oblongata, and the pons. It plays the extremely important role of connecting the brain to the rest of the body via the spinal cord.<\/em><\/figcaption><\/figure>\nThe\u00a0hindbrain<\/a>, <\/strong>which includes the cerebellum<\/a>, medulla oblongata<\/a>, and the pons<\/a>. The hindbrain is the lowest part of the brain. It resembles a stalk and platform on which the cerebrum is perched. The components of the hindbrain connect the rest of the brain with the spinal cord and passes nerve impulses between the brain and spinal cord.<\/p>\nCerebellum<\/h3>\n
The\u00a0cerebellum<\/a><\/strong> is located just below the cerebrum and at the back of the brain behind the brain stem. It coordinates your voluntary movements, balance, and posture.\u00a0 Information from your inner ear, joints and muscles, and eyes are all knitted together in the cerebellum so that you have awareness of where you are in 3-dimensional space.\u00a0 Patients who have suffered damage to their cerebellum may suffer from balance disorder. In addition the cerebellum plays a major role in motor learning (like how to ride a bike or how to do a backflip on a trampoline) through trial and error.\u00a0 While traditionally, the cerebellum was thought to only be involved in motor functions, we now know that it also plays an important role in memory and learning.<\/p>\nMedulla Oblongata<\/h3>\n
The\u00a0medulla oblongata<\/a><\/strong> makes up part of the brainstem and sits in front of and just below the cerebellum, at the very top of the spinal cord.\u00a0 It is responsible for control of heart rate, respiration rate and blood pressure, as well as reflexes such as vomiting, coughing, sneezing and swallowing.<\/p>\nPons<\/h3>\n
The\u00a0pons<\/a><\/strong> is located in front of the cerebellum and above the medulla oblongata.\u00a0 It has several functions, including receiving sensory information from the face, regulating rate and depth of breaths, as well as sleep cycles.<\/p>\nMidbrain<\/h2>\nFigure 8.5.5 The brainstem includes the midbrain, the pons and the medulla oblongata.<\/em><\/figcaption><\/figure>\nThe midbrain is the topmost part of the brainstem and is the essential connection between and brain and spinal cord.\u00a0 The three main parts of the midbrain are the colliculi, the tegmentum, and the cerebral peduncles.\u00a0 These structures are all considered part of the brainstem, which consists of the medulla oblongata, the pons and the midbrain.<\/p>\n
Reticular Activating System<\/h3>\n
The reticular activating system<\/a> (RAS) is responsible for the sleep-wake cycle and wakefulness.\u00a0 It also regulates attention, ability to focus and arousal.<\/p>\nForebrain<\/h2>\n
The forebrain is the anterior (forwardmost) part of the brain and includes the cerebrum, the thalamus and hypothalamus, hippocampus, amygdala, and limbic system.\u00a0 This portion of the brain is responsible for processing incoming sensory information, performing complex cognitive activities (speech, abstract thought, etc) and governing voluntary motor movements.\u00a0 \u00a0The forebrain also controls body temperature, reproductive functions, eating, sleeping and the display of emotions.<\/p>\n
Cerebrum<\/h3>\n
The\u00a0cerebrum<\/a><\/strong>\u00a0is the largest part of the brain. It controls conscious, intellectual functions.\u00a0Among other things,\u00a0it controls reasoning, language, memory, sight, touch, and hearing. When you read a book, play a video game, or recognize a classmate, you are using your cerebrum.<\/p>\nHemispheres and Lateralization of the Cerebrum<\/h4>\n
The cerebrum is divided from front to back into two halves called the left and right\u00a0hemispheres<\/a>.<\/strong>\u00a0The two hemispheres are connected by a thick bundle of axons, known as the corpus callosum<\/a>, which lies deep within the brain. The corpus callosum is the main avenue of\u00a0communication between the two hemispheres. It connects each point in the cerebrum to the mirror-image point in the opposite hemisphere.<\/p>\nThe right and left hemispheres of the cerebrum are similar in shape, and most areas of cerebrum are found in both hemispheres. Some areas, however, show\u00a0lateralization<\/a>,<\/strong>\u00a0or a\u00a0concentration\u00a0in one hemisphere or the other.\u00a0In most people, for example, language functions are more concentrated in the left hemisphere, whereas abstract reasoning and visual-spatial abilities are more concentrated in the right hemisphere.<\/p>\nFor reasons that are not yet clear, each hemisphere of the brain interacts primarily with the opposite side of the body. The left side of the brain receives messages from and sends commands to the right side of the body, and the right side of the brain\u00a0receives messages from and sends commands to the left side of the body. Sensory nerves from the spinal cord to the brain and motor nerves from the brain to the spinal cord both cross the midline of the body at the level of the brain stem.<\/p>\n
Lobes of the Cerebrum<\/h4>\n
Each hemisphere<\/a> of the cerebrum is further divided into the four lobes shown in Figure 8.5.6 and described below.<\/p>\nFigure 8.5.6 The cerebrum is organized into four lobes: frontal, parietal, occipital, and temporal.<\/em><\/figcaption><\/figure>\n\nEach hemisphere of the cerebrum consists of four parts, called lobes. Each lobe is associated with particular brain functions. Just one function of each lobe is listed here.<\/p>\n<\/div>\n
\n- The\u00a0frontal lobes<\/a><\/strong>\u00a0are located at the front of the brain behind the forehead. The frontal lobes are associated with executive functions, such as attention, self-control, planning, problem solving, reasoning, abstract thought, language, and personality.<\/li>\n
- The\u00a0parietal lobes<\/a><\/strong>\u00a0are located behind the frontal lobes at the top of the head. The parietal lobes are involved in sensation \u2014 including\u00a0temperature, touch, and taste. Reading and arithmetic are also functions of the parietal lobes.<\/li>\n
- The\u00a0temporal lobes<\/a><\/strong>\u00a0are located at the sides of the head below the frontal and parietal lobes. The temporal lobes enable hearing, the formation and retrieval of memories, and the integration of memories and sensations.<\/li>\n
- The\u00a0occipital lobes<\/a><\/strong>\u00a0are located at the back of the head below the parietal lobes. The occipital lobes are the smallest of the four pairs of lobes. They are dedicated almost solely to\u00a0vision.<\/li>\n<\/ul>\n
Cerebral Cortex<\/h4>\n
Most of the information processing in the brain actually takes place in the\u00a0cerebral cortex<\/a><\/strong>, a rind of gray matter and other tissues just a few millimetres thick that makes up the outer surface of the cerebrum in both hemispheres of the brain. The cerebral cortex has many folds in it, greatly increasing the amount of surface area of the brain that can fit within the skull. Because of all the folds in the human cerebral cortex, it has a surface area of about 2,500 cm2<\/sup>\u00a0(2.5 ft2<\/sup>). The size and importance of the cerebral cortex is far greater in the human brain than the brains of any other vertebrates, including nonhuman\u00a0primates.<\/p>\nThe Limbic System<\/h3>\n
The limbic system consists of the hypothalamus, thalamus, the hippocampus and amygdala. The structures and interacting areas of the\u00a0limbic system<\/a><\/b>\u00a0are involved in motivation, emotion, learning, and memory.<\/p>\nThalamus and Hypothalamus<\/h4>\n
Several structures are located deep within the brain and are important for communication between the brain and spinal cord (or the rest of the body). These structures include the hypothalamus and thalamus. The diagram below (Figure 8.5.7) shows where these structures are located in the brain. Like the two halves of the cerebrum, the hypothalamus and thalamus exist in two halves, one in each hemisphere.<\/p>\nFigure 8.5.7 Structures deep within the brain include the hypothalamus and thalamus.<\/em><\/figcaption><\/figure>\nThe\u00a0hypothalamus<\/a><\/strong>\u00a0is located just above the brain stem, and is about the size of an almond. The hypothalamus is responsible for certain metabolic processes and other activities of the autonomic nervous system<\/a>, including body\u00a0temperature,\u00a0heart\u00a0rate, hunger, thirst, fatigue, sleep, wakefulness, and circadian (24-hour) rhythms. The hypothalamus is also an important emotional center of the brain. The hypothalamus can regulate so many body functions because it responds to many different internal and external signals, including messages from the brain, light, steroid hormones, stress, and invading pathogens, among others.<\/p>\nOne way the hypothalamus influences body functions is by synthesizing hormones that directly influence body processes. It synthesizes the hormone oxytocin<\/a>, which stimulates uterine contractions during childbirth and the letdown of milk during lactation. It also synthesizes antidiuretic hormone<\/a>, which stimulates the kidneys to reabsorb more water and excrete more concentrated urine. These two hormones are sent from the hypothalamus via a stalk-like structure called the infundibulum (see Figure 8.5.7) directly to the posterior (back) portion of the pituitary gland, which secretes them into the blood.<\/p>\nThe main way the hypothalamus influences body functions is by controlling the\u00a0pituitary gland<\/a>, known as the master gland of the\u00a0endocrine system. The hypothalamus synthesizes neurohormones called releasing factors that travel through the infundibulum directly to the anterior (front) part of the pituitary gland. The releasing factors generally either stimulate or inhibit the secretion of anterior pituitary hormones, most of which control other glands of the endocrine system.<\/p>\n
Figure 8.5.6 The cerebrum is organized into four lobes: frontal, parietal, occipital, and temporal.<\/em>[\/caption]\r\n\r\n- \r\n \t
- The\u00a0[pb_glossary id=\"6021\"]frontal lobes[\/pb_glossary]<\/strong>\u00a0are located at the front of the brain behind the forehead. The frontal lobes are associated with executive functions, such as attention, self-control, planning, problem solving, reasoning, abstract thought, language, and personality.<\/li>\r\n \t
- The\u00a0[pb_glossary id=\"3088\"]parietal lobes[\/pb_glossary]<\/strong>\u00a0are located behind the frontal lobes at the top of the head. The parietal lobes are involved in sensation \u2014 including\u00a0temperature, touch, and taste. Reading and arithmetic are also functions of the parietal lobes.<\/li>\r\n \t
- The\u00a0[pb_glossary id=\"3089\"]temporal lobes[\/pb_glossary]<\/strong>\u00a0are located at the sides of the head below the frontal and parietal lobes. The temporal lobes enable hearing, the formation and retrieval of memories, and the integration of memories and sensations.<\/li>\r\n \t
- The\u00a0[pb_glossary id=\"3090\"]occipital lobes[\/pb_glossary]<\/strong>\u00a0are located at the back of the head below the parietal lobes. The occipital lobes are the smallest of the four pairs of lobes. They are dedicated almost solely to\u00a0vision.<\/li>\r\n<\/ul>\r\n
Cerebral Cortex<\/h4>\r\nMost of the information processing in the brain actually takes place in the\u00a0[pb_glossary id=\"5937\"]cerebral cortex[\/pb_glossary]<\/strong>, a rind of gray matter and other tissues just a few millimetres thick that makes up the outer surface of the cerebrum in both hemispheres of the brain. The cerebral cortex has many folds in it, greatly increasing the amount of surface area of the brain that can fit within the skull. Because of all the folds in the human cerebral cortex, it has a surface area of about 2,500 cm2<\/sup>\u00a0(2.5 ft2<\/sup>). The size and importance of the cerebral cortex is far greater in the human brain than the brains of any other vertebrates, including nonhuman\u00a0primates.\r\n
The Limbic System<\/h3>\r\nThe limbic system consists of the hypothalamus, thalamus, the hippocampus and amygdala. The structures and interacting areas of the\u00a0[pb_glossary id=\"3098\"]limbic system[\/pb_glossary]<\/b>\u00a0are involved in motivation, emotion, learning, and memory.\r\n
Thalamus and Hypothalamus<\/h4>\r\nSeveral structures are located deep within the brain and are important for communication between the brain and spinal cord (or the rest of the body). These structures include the hypothalamus and thalamus. The diagram below (Figure 8.5.7) shows where these structures are located in the brain. Like the two halves of the cerebrum, the hypothalamus and thalamus exist in two halves, one in each hemisphere.\r\n\r\n[caption id=\"attachment_3092\" align=\"alignleft\" width=\"363\"]
Figure 8.5.7 Structures deep within the brain include the hypothalamus and thalamus.<\/em>[\/caption]\r\n\r\nThe\u00a0[pb_glossary id=\"2937\"]hypothalamus[\/pb_glossary]<\/strong>\u00a0is located just above the brain stem, and is about the size of an almond. The hypothalamus is responsible for certain metabolic processes and other activities of the [pb_glossary id=\"5899\"]autonomic nervous system[\/pb_glossary], including body\u00a0temperature,\u00a0heart\u00a0rate, hunger, thirst, fatigue, sleep, wakefulness, and circadian (24-hour) rhythms. The hypothalamus is also an important emotional center of the brain. The hypothalamus can regulate so many body functions because it responds to many different internal and external signals, including messages from the brain, light, steroid hormones, stress, and invading pathogens, among others.\r\n\r\nOne way the hypothalamus influences body functions is by synthesizing hormones that directly influence body processes. It synthesizes the hormone [pb_glossary id=\"3093\"]oxytocin[\/pb_glossary], which stimulates uterine contractions during childbirth and the letdown of milk during lactation. It also synthesizes [pb_glossary id=\"5893\"]antidiuretic hormone[\/pb_glossary], which stimulates the kidneys to reabsorb more water and excrete more concentrated urine. These two hormones are sent from the hypothalamus via a stalk-like structure called the infundibulum (see Figure 8.5.7) directly to the posterior (back) portion of the pituitary gland, which secretes them into the blood.\r\n\r\nThe main way the hypothalamus influences body functions is by controlling the\u00a0[pb_glossary id=\"2938\"]pituitary gland[\/pb_glossary], known as the master gland of the\u00a0endocrine system. The hypothalamus synthesizes neurohormones called releasing factors that travel through the infundibulum directly to the anterior (front) part of the pituitary gland. The releasing factors generally either stimulate or inhibit the secretion of anterior pituitary hormones, most of which control other glands of the endocrine system.\r\n\r\nThe\u00a0[pb_glossary id=\"3095\"]thalamus[\/pb_glossary],<\/strong> which is located near the hypothalamus (see Figure 8.5.7), is a major hub for information traveling back and forth between the spinal cord and cerebrum. It relays sensory signals to the cerebral cortex and motor signals to the spinal cord. It is also involved in the regulation of consciousness, sleep, and alertness.\r\n\r\nHippocampus and Amygdala<\/h4>\r\nThe [pb_glossary id=\"3096\"]hippocampus[\/pb_glossary] is a complex structure embedded deep in the temporal lobe.\u00a0 It plays a major role in learning and memory and contributes to regulation of motivation and emotion. The amygdala is the part of the brain responsible for formation and storage of memories associated with emotional events.\r\n\r\nWatch \"The Limbic System\" by Soton Brain Hub to learn about the location and functions of the limbic system.\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=jcrWPo_s6EE\r\n
The Limbic System, Soton Brain Hub, 2016.<\/p>\r\n\r\n
Spinal Cord<\/h1>\r\n<\/div>\r\nThe\u00a0[pb_glossary id=\"3010\"]spinal cord[\/pb_glossary]<\/strong> is a long, thin, tubular bundle of nervous tissues that extends from the brain stem and continues down the center of the back to the pelvis. It is highlighted in yellow in Figure 8.5.8. The spinal cord is enclosed within, but is shorter than, the vertebral column.\r\n\r\n[caption id=\"attachment_3099\" align=\"alignnone\" width=\"482\"]
Figure 8.5.8 The spinal cord (yellow) runs from the bottom of the brain to the lower back.<\/em>[\/caption]\r\nStructure of the Spinal Cord<\/h2>\r\nThe center of the spinal cord consists of gray matter, which is made up mainly of cell bodies of neurons, including interneurons and motor neurons. The gray matter is surrounded by white matter that consists mainly of myelinated axons of motor and sensory neurons. Spinal nerves, which connect the spinal cord to the PNS, exit from the spinal cord between vertebrae (see Figure 8.5.9).\r\n\r\n \r\n
\r\n\r\n[caption id=\"attachment_3100\" align=\"alignleft\" width=\"291\"] Figure 8.5.9 This model shows three vertebrae (white) with branching spinal nerves (yellow) emerging from the either side of the spinal cord between vertebrae.<\/em>[\/caption]\r\n\r\n<\/div>\r\nFunctions of the Spinal Cord<\/h2>\r\nThe spinal cord serves as an information superhighway. It passes messages from the body to the brain and from the brain to the body. Sensory (afferent) nerves carry\u00a0nerve impulses\u00a0to the brain from sensory receptor\u00a0cells\u00a0everywhere in and on the body. Motor (efferent) nerves carry nerve impulses away from the brain to glands, organs, or\u00a0muscles throughout the body.\r\n\r\nThe spinal cord also independently controls certain rapid responses called\u00a0reflexes<\/strong> without any input from the brain. You can see how this may happen in Figure 8.5.10. A sensory receptor responds to a sensation and sends a nerve impulse along a sensory nerve to the spinal cord. In the spinal cord, the message passes to an interneuron and from the interneuron to a motor nerve, which carries the impulse to a muscle. The muscle contracts in response. These neuron connections form a reflex arc, which requires no input from the brain. No doubt you have experienced such reflex actions yourself. For example, you may have reached out to touch a pot on the stove, not realizing that it was very hot. Virtually at the same moment that you feel the burning heat, you jerk your arm back and remove your hand from the pot.\r\n\r\n \r\n
\r\n\r\n[caption id=\"attachment_3101\" align=\"alignnone\" width=\"1038\"] Figure 8.5.10 This diagram shows what happens in a long reflex (top), in which sensory nerves carry the message all the way to the spinal cord; and in a short reflex (bottom), in which sensory nerves travel only to a ganglion outside the spinal cord. Note that interneurons are involved in reflexes, connecting sensory and motor neurons, but they are not actually shown in the diagram.<\/em>[\/caption]\r\n\r\n<\/div>\r\nInjuries to the Spinal Cord<\/h2>\r\nPhysical damage to the spinal cord may result in\u00a0[pb_glossary id=\"3102\"]paralysis[\/pb_glossary],<\/strong> which is loss of sensation and movement in part of the body. Paralysis generally affects all the areas of the body below the level of the injury, because nerve impulses are interrupted and can no longer travel back and forth between the brain and body beyond that point. If an injury to the spinal cord produces nothing more than swelling, the symptoms may be transient. However, if nerve fibres (axons) in the spinal cord are badly damaged, the loss of function may be permanent. Experimental studies have shown that spinal nerve fibres attempt to regrow, but tissue destruction usually produces scar tissue that cannot be penetrated by the regrowing nerves, as well other factors that inhibit nerve fibre regrowth in the central nervous system.\r\n
\r\nFeature: My\u00a0Human Body<\/h1>\r\n<\/div>\r\nEach year, many millions of people have a stroke<\/a>, and stroke is the second leading cause of death in adults.\u00a0[pb_glossary id=\"3103\"]Stroke[\/pb_glossary],<\/strong>\u00a0also known as cerebrovascular accident, occurs when poor blood flow to the brain results in the death of brain cells. There are two main types of strokes:\r\n
- \r\n \t
- Ischemic strokes occur due to lack of blood flow because of a blood clot in an artery going to the brain.<\/li>\r\n \t
- Hemorrhagic strokes occur due to bleeding from a broken blood vessel in the brain.<\/li>\r\n<\/ul>\r\nEither type of stroke may result in paralysis, loss of the ability to speak or comprehend speech, loss of bladder control, personality changes, and many other potential effects, depending on the part of the brain that is injured. The effects of a stroke may be mild and transient or more severe and permanent. A stroke may even be fatal. It generally depends on the type of stroke and how extensive it is.\r\n\r\nAre you at risk of a stroke? The main risk factor for stroke is age \u2014 about two-thirds of strokes occur in people over the age of 65. There is nothing you can do about your age, but most other stroke risk factors can be reduced with lifestyle changes or medications. The risk factors include high blood pressure, tobacco smoking, obesity, high blood cholesterol, diabetes mellitus, and atrial fibrillation.\r\n\r\nChances are good that you or someone you know is at risk of a stroke, so it is important to recognize a stroke if one occurs. A stroke is a medical emergency, and the more quickly treatment is given, the better the outcome is likely to be. In the case of ischemic strokes, the use of clot-busting drugs may prevent permanent brain damage if administered within three or four hours of the stroke. Remembering the signs of a stroke is easy. They are summed up by the acronym FAST.\r\n\r\n
\r\n 8.5 Summary<\/span><\/h1>\r\n<\/header>\r\n
\r\n- \r\n \t
- The [pb_glossary id=\"5933\"]central nervous system[\/pb_glossary] is the part of the nervous system that includes the [pb_glossary id=\"5915\"]brain[\/pb_glossary] and [pb_glossary id=\"3010\"]spinal cord[\/pb_glossary]. It is physically protected by\u00a0bones, meninges, and [pb_glossary id=\"5939\"]cerebrospinal fluid[\/pb_glossary]. It is chemically protected by the blood-brain barrier.<\/li>\r\n \t
- The brain is the control center of the nervous system and of the entire organism. The brain uses a relatively large proportion of the body\u2019s\u00a0energy, primarily in the form of glucose.<\/li>\r\n \t
- The brain is divided into three major parts, each with different functions: the hindbrain, the midbrain and the forebrain.<\/li>\r\n \t
- Hindbrain consists of the medulla oblongata, the pons and the cerebellum, each of which perform specific functions.<\/li>\r\n \t
- The midbrain is primarily responsible for motor movement and in auditory and visual processing.<\/li>\r\n \t
- The forebrain contains many structures including:\r\n
- \r\n \t
- The cerebrum, which is further divided into left and right hemispheres. Each hemisphere has four lobes: frontal, parietal, temporal, and occipital. Each lobe is associated with specific senses or other functions.<\/li>\r\n \t
- The cerebrum\u00a0has a\u00a0thin outer layer called the cerebral cortex. Its many folds give it a large surface area. This is where most information processing takes place.<\/li>\r\n \t
- Inner structures of the brain include the hypothalamus \u2014 which controls the\u00a0endocrine system\u00a0via the\u00a0pituitary gland\u00a0\u2014 and the thalamus, which has several involuntary functions.<\/li>\r\n \t
- The hippocampus and amygdala, which are part of the limbic system and play important roles in memory, learning and emotions.<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t
- The spinal cord is a tubular bundle of nervous tissues that extends from the head down the middle of the back to the pelvis. It functions mainly to connect the brain with the\u00a0peripheral nervous system. It also controls certain rapid responses called reflexes without any input from the brain.<\/li>\r\n \t
- A spinal cord injury may lead to paralysis (loss of sensation and movement) of the body below the level of the injury, because nerve impulses can no longer travel up and down the spinal cord beyond that point.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n 8.5 Review Questions<\/span><\/h1>\r\n<\/header>\r\n
\r\n- \r\n \t
- What is the central nervous system?<\/li>\r\n \t
- How is the central nervous system protected?<\/li>\r\n \t
- What is the overall function of the brain?<\/li>\r\n \t
- Identify the three main parts of the brain and one function of each part.<\/li>\r\n \t
- Describe the hemispheres of the brain.<\/li>\r\n \t
- Explain and give examples of lateralization of the brain.<\/li>\r\n \t
- Identify one function of each of the four lobes of the cerebrum.<\/li>\r\n \t
- [h5p id=\"562\"]<\/li>\r\n \t
- [h5p id=\"563\"]<\/li>\r\n \t
- Summarize the structure and function of the cerebral cortex. Explain how the hypothalamus controls the endocrine system.<\/li>\r\n \t
- Describe the spinal cord.<\/li>\r\n \t
- What is the main function of the spinal cord?<\/li>\r\n \t
- Explain how reflex actions occur.<\/li>\r\n \t
- Why do severe spinal cord injuries usually cause paralysis?<\/li>\r\n \t
- What do you think are some possible consequences of severe damage to the brain stem? How might this compare to the consequences of severe damage to the frontal lobe? Explain your answer.<\/li>\r\n \t
- Information travels very quickly in the nervous system, but generally, the longer the path between areas, the longer it takes. Based on this, explain why you think reflexes often occur at the spinal cord level, and do not require input from the brain.<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
\r\n 8.5 Explore More<\/span><\/h1>\r\n<\/header>\r\n
\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=sewhbmh0ECg\r\nWhat if we could look inside human brains? - Moran Cerf, TED-Ed, 2013.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=ZMSbDwpIyF4\r\n
The left brain vs. right brain myth - Elizabeth Waters, TED-Ed, 2017.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?time_continue=1&v=aCv4K5aStdU&feature=emb_logo\r\n
Split-brain patient 'Joe' being tested with stimuli presented in different visual fields,\r\nmarkmcdermott, 2010.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n
Attributes<\/h2>\r\nFigure 8.5.1<\/strong>\r\n\r\nSensory_Homunculus-en.svg<\/a> by Popadius<\/a> on Wikimedia Commons is used under a CC BY 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0\/deed.en) license. (This is a derivative work from File:1421 Sensory Homunculus<\/a>.jpg by OpenStax College<\/a>)\r\n\r\nFigure 8.5.2<\/strong>\r\n\r\nOverview_of_Nervous_System<\/a>\u00a0by OpenStax<\/a> on Wikimedia Commons is used under a CC BY 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en) license.\r\n\r\nFigure 8.5.3<\/strong>\r\n\r\nDiagram_showing_the_brain_stem_which_includes_the_medulla_oblongata,_the_pons_and_the_midbrain_(2)_CRUK_294.svg<\/a> by Cancer Research UK<\/a> on Wikimedia Commons is used under a CC BY-SA 4.0 <\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\nFigure 8.5.4<\/strong>\r\n\r\nBrain_bulbar_region.svg<\/a> by Fvasconcellos<\/a> on Wikimedia Commons is used under a CC BY 2.5<\/a> license (derivative work from Brain human sagittal section.svg<\/a>\u00a0 by Patrick J. Lynch; Brain bulbar region.PNG<\/a> by DO11.10<\/a>).\r\n\r\nFigure 8.5.5<\/strong>\r\n\r\nMidbrain<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY 3.0 <\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0) license.\r\n\r\nFigure 8.5.6<\/strong>\r\n\r\nBrainLobes<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY 3.0 <\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0) license.\u00a0<\/span>\r\n\r\nFigure 8.5.7<\/strong>\r\n\r\nDiencephalon<\/a> by OpenStax<\/a> Wikimedia Commons is used under a CC BY 4.0 <\/a>(https:\/\/creativecommons.org\/licenses\/by\/4.0) license.\r\n\r\nFigure 8.5.8<\/strong>\r\n\r\nSpinalCord<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY 3.0 <\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0) license.\u00a0<\/span>\r\n\r\nFigure 8.5.9<\/strong>\r\n\r\nSpinal_readjustment_3<\/a> by Tomwsulcer<\/a> on\u00a0 Wikimedia Commons is used under a CC0 1.0<\/a> Universal Public Domain Dedication license (https:\/\/creativecommons.org\/publicdomain\/zero\/1.0\/deed.en).\r\n\r\nFigure 8.5.10<\/strong>\r\n\r\n1507_Short_and_Long_Reflexes<\/a> by OpenStax<\/a> on Wikimedia Commons is used under a CC BY 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en) license.\r\n
References<\/h2>\r\n
Betts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2013, 28 May). Figure 14.23<\/span>\u00a0<\/span>The sensory homunculus <\/span>[digital image]. In Anatomy and Physiology<\/em> (Section 14.2). OpenStax. https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/14-2-central-processing\r\n<\/span><\/span><\/p>\r\n
Betts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2013, 28 May). Figure 15.8 Short and long reflexes [digital image]. In Anatomy and Physiology<\/em> (Section 15.2). OpenStax. https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/15-2-autonomic-reflexes-and-homeostasis<\/p>\r\n
Betts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2016, May 18). <\/span><\/span>Figure 12.2 Central and peripheral nervous system [digital image]. In Anatomy and Physiology<\/em> (Section 12.1). https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/12-1-basic-structure-and-function-of-the-nervous-system<\/span><\/span><\/p>\r\n
Betts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2016, May 18). Figure 13.11 The diencephalon [digital image]. In Anatomy and Physiology<\/em> (Section 13.2). https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/13-2-the-central-nervous-system<\/p>\r\n
Blausen.com staff. (2014). Medical gallery of Blausen Medical 2014. WikiJournal of Medicine,<\/em> 1<\/em> (2). DOI:10.15347\/wjm\/2014.010. ISSN 2002-4436<\/span><\/p>\r\n
markmcdermott. (2010). Split-brain patient 'Joe' being tested with stimuli presented in different visual fields. YouTube. https:\/\/www.youtube.com\/user\/markmcdermott\/search?query=split<\/p>\r\n
Mayo Clinic Staff. (n.d.). Stroke [online article]. MayoClinic.org. https:\/\/www.mayoclinic.org\/diseases-conditions\/stroke\/symptoms-causes\/syc-20350113<\/p>\r\n
Soton Brain Hub. (2016, July 29). The limbic system. YouTube. https:\/\/www.youtube.com\/watch?v=jcrWPo_s6EE&feature=youtu.be<\/p>\r\n
TED-Ed. (2013, January 31). What if we could look inside human brains? - Moran Cerf. YouTube. https:\/\/www.youtube.com\/watch?v=sewhbmh0ECg&feature=youtu.be<\/p>\r\n
TED-Ed. (2017, July 24). The left brain vs. right brain myth - Elizabeth Waters. YouTube. https:\/\/www.youtube.com\/watch?v=ZMSbDwpIyF4&feature=youtu.be<\/p>\r\n ","rendered":"
<\/p>\n
Figure 8.5.1 This picture is called an <\/em>homunculus.\u00a0<\/em><\/figcaption><\/figure>\n Homunculus<\/h1>\n
The very odd-looking drawing in Figure 8.5.1 is called a homunculus. The beige mass represents a cross-sectional wedge of the human brain, and the drawing shows some areas of the brain associated with different parts of the body. As you can see, larger areas of the brain in this region are associated with the hands, face, and tongue, as compared to the areas associated with the legs and feet. Given the importance of speech, manual dexterity, and face-to-face social interactions in human beings, it is not surprising that relatively large areas of the brain are needed to control these body parts. The brain is the most complex organ in the human body and part of the central nervous system.<\/p>\n
\nWhat Is the Central Nervous System?<\/h1>\n<\/div>\n
The central nervous system<\/a> (CNS) is the part of the nervous system that includes the brain<\/a> and spinal cord<\/a>. The drawing below (Figure 8.5.2) shows the central nervous system as one of two main divisions of the total nervous system. The other main division is the peripheral nervous system<\/a> (PNS). The CNS and PNS work together to control virtually all body functions.<\/p>\n
Figure 8.5.2 The two main divisions of the nervous system: the central nervous system (CNS) \u2014 which includes the brain and spinal cord \u2014 and the peripheral nervous system (PNS), which includes nerves and ganglia (singular, ganglion), which transmit information between the CNS to the rest of the body.<\/em><\/figcaption><\/figure>\n The delicate nervous tissues of the central nervous system are protected by major physical and chemical barriers. Physically, the brain and spinal cord are surrounded by tough meninges<\/a>, a three-layer protective sheath that also contains cushioning cerebrospinal fluid<\/a>. The\u00a0bones\u00a0of the skull and spinal vertebrae also contribute to physically protecting the brain and spinal cord. Chemically, the brain and spinal cord are isolated from the circulation\u00a0\u2014\u00a0and most toxins or pathogens in the\u00a0blood\u00a0\u2014\u00a0by the\u00a0blood-brain barrier<\/a>.<\/strong>\u00a0The blood-brain barrier is a highly selective membrane formed of endothelial\u00a0cells\u00a0that separates the circulating\u00a0blood\u00a0from extracellular fluid in the CNS. The barrier allows\u00a0water, certain gases, glucose, and some other molecules needed by the brain and spinal cord to cross from the blood into the CNS, while keeping out potentially harmful substances. These physical and chemical barriers make the CNS less susceptible to injury than the PNS. However, damage to the CNS is likely to have more serious consequences.<\/p>\n
\nThe Brain<\/h1>\n<\/div>\n
The\u00a0brain<\/a><\/strong> is the control center of not only the rest of the nervous system, but of the entire organism. The adult brain makes up only about 2% of the body\u2019s weight, but it uses about 20% of the body\u2019s total energy. The brain contains an estimated 100 billion neurons, and each neuron<\/a> has thousands of synaptic connections to other neurons. The brain also has about the same number of neuroglia<\/a> as neurons. No wonder the brain uses so much energy! In addition, the brain uses mostly glucose<\/a> for energy. As a result, if the brain is deprived of glucose, it can lead to unconsciousness. The brain is able to store some glucose in the form of glycogen, but in much smaller amounts than are found in the liver and skeletal muscles.<\/p>\n
The brain controls such mental processes as reasoning, imagination, memory, and language. It also interprets information from the senses and commands the body to respond appropriately. It controls basic physical processes (such as breathing and heartbeat), as well as voluntary activities (such as walking and writing). The brain has three major regions: the hindbrain, the midbrain and the forebrain. These parts are shown in Figure 8.5.3 and described below.<\/p>\n
Figure 8.5.3 Diagram of the forebrain, midbrain and hindbrain. <\/em><\/figcaption><\/figure>\n \n<\/p>\n<\/div>\n
The Hindbrain<\/h2>\n
Figure 8.5.4 The hindbrain consists of the cerebellum,<\/em> medulla oblongata, and the pons. It plays the extremely important role of connecting the brain to the rest of the body via the spinal cord.<\/em><\/figcaption><\/figure>\n The\u00a0hindbrain<\/a>, <\/strong>which includes the cerebellum<\/a>, medulla oblongata<\/a>, and the pons<\/a>. The hindbrain is the lowest part of the brain. It resembles a stalk and platform on which the cerebrum is perched. The components of the hindbrain connect the rest of the brain with the spinal cord and passes nerve impulses between the brain and spinal cord.<\/p>\n
Cerebellum<\/h3>\n
The\u00a0cerebellum<\/a><\/strong> is located just below the cerebrum and at the back of the brain behind the brain stem. It coordinates your voluntary movements, balance, and posture.\u00a0 Information from your inner ear, joints and muscles, and eyes are all knitted together in the cerebellum so that you have awareness of where you are in 3-dimensional space.\u00a0 Patients who have suffered damage to their cerebellum may suffer from balance disorder. In addition the cerebellum plays a major role in motor learning (like how to ride a bike or how to do a backflip on a trampoline) through trial and error.\u00a0 While traditionally, the cerebellum was thought to only be involved in motor functions, we now know that it also plays an important role in memory and learning.<\/p>\n
Medulla Oblongata<\/h3>\n
The\u00a0medulla oblongata<\/a><\/strong> makes up part of the brainstem and sits in front of and just below the cerebellum, at the very top of the spinal cord.\u00a0 It is responsible for control of heart rate, respiration rate and blood pressure, as well as reflexes such as vomiting, coughing, sneezing and swallowing.<\/p>\n
Pons<\/h3>\n
The\u00a0pons<\/a><\/strong> is located in front of the cerebellum and above the medulla oblongata.\u00a0 It has several functions, including receiving sensory information from the face, regulating rate and depth of breaths, as well as sleep cycles.<\/p>\n
Midbrain<\/h2>\n
Figure 8.5.5 The brainstem includes the midbrain, the pons and the medulla oblongata.<\/em><\/figcaption><\/figure>\n The midbrain is the topmost part of the brainstem and is the essential connection between and brain and spinal cord.\u00a0 The three main parts of the midbrain are the colliculi, the tegmentum, and the cerebral peduncles.\u00a0 These structures are all considered part of the brainstem, which consists of the medulla oblongata, the pons and the midbrain.<\/p>\n
Reticular Activating System<\/h3>\n
The reticular activating system<\/a> (RAS) is responsible for the sleep-wake cycle and wakefulness.\u00a0 It also regulates attention, ability to focus and arousal.<\/p>\n
Forebrain<\/h2>\n
The forebrain is the anterior (forwardmost) part of the brain and includes the cerebrum, the thalamus and hypothalamus, hippocampus, amygdala, and limbic system.\u00a0 This portion of the brain is responsible for processing incoming sensory information, performing complex cognitive activities (speech, abstract thought, etc) and governing voluntary motor movements.\u00a0 \u00a0The forebrain also controls body temperature, reproductive functions, eating, sleeping and the display of emotions.<\/p>\n
Cerebrum<\/h3>\n
The\u00a0cerebrum<\/a><\/strong>\u00a0is the largest part of the brain. It controls conscious, intellectual functions.\u00a0Among other things,\u00a0it controls reasoning, language, memory, sight, touch, and hearing. When you read a book, play a video game, or recognize a classmate, you are using your cerebrum.<\/p>\n
Hemispheres and Lateralization of the Cerebrum<\/h4>\n
The cerebrum is divided from front to back into two halves called the left and right\u00a0hemispheres<\/a>.<\/strong>\u00a0The two hemispheres are connected by a thick bundle of axons, known as the corpus callosum<\/a>, which lies deep within the brain. The corpus callosum is the main avenue of\u00a0communication between the two hemispheres. It connects each point in the cerebrum to the mirror-image point in the opposite hemisphere.<\/p>\n
The right and left hemispheres of the cerebrum are similar in shape, and most areas of cerebrum are found in both hemispheres. Some areas, however, show\u00a0lateralization<\/a>,<\/strong>\u00a0or a\u00a0concentration\u00a0in one hemisphere or the other.\u00a0In most people, for example, language functions are more concentrated in the left hemisphere, whereas abstract reasoning and visual-spatial abilities are more concentrated in the right hemisphere.<\/p>\n
For reasons that are not yet clear, each hemisphere of the brain interacts primarily with the opposite side of the body. The left side of the brain receives messages from and sends commands to the right side of the body, and the right side of the brain\u00a0receives messages from and sends commands to the left side of the body. Sensory nerves from the spinal cord to the brain and motor nerves from the brain to the spinal cord both cross the midline of the body at the level of the brain stem.<\/p>\n
Lobes of the Cerebrum<\/h4>\n
Each hemisphere<\/a> of the cerebrum is further divided into the four lobes shown in Figure 8.5.6 and described below.<\/p>\n
Figure 8.5.6 The cerebrum is organized into four lobes: frontal, parietal, occipital, and temporal.<\/em><\/figcaption><\/figure>\n \nEach hemisphere of the cerebrum consists of four parts, called lobes. Each lobe is associated with particular brain functions. Just one function of each lobe is listed here.<\/p>\n<\/div>\n
- \n
- The\u00a0frontal lobes<\/a><\/strong>\u00a0are located at the front of the brain behind the forehead. The frontal lobes are associated with executive functions, such as attention, self-control, planning, problem solving, reasoning, abstract thought, language, and personality.<\/li>\n
- The\u00a0parietal lobes<\/a><\/strong>\u00a0are located behind the frontal lobes at the top of the head. The parietal lobes are involved in sensation \u2014 including\u00a0temperature, touch, and taste. Reading and arithmetic are also functions of the parietal lobes.<\/li>\n
- The\u00a0temporal lobes<\/a><\/strong>\u00a0are located at the sides of the head below the frontal and parietal lobes. The temporal lobes enable hearing, the formation and retrieval of memories, and the integration of memories and sensations.<\/li>\n
- The\u00a0occipital lobes<\/a><\/strong>\u00a0are located at the back of the head below the parietal lobes. The occipital lobes are the smallest of the four pairs of lobes. They are dedicated almost solely to\u00a0vision.<\/li>\n<\/ul>\n
Cerebral Cortex<\/h4>\n
Most of the information processing in the brain actually takes place in the\u00a0cerebral cortex<\/a><\/strong>, a rind of gray matter and other tissues just a few millimetres thick that makes up the outer surface of the cerebrum in both hemispheres of the brain. The cerebral cortex has many folds in it, greatly increasing the amount of surface area of the brain that can fit within the skull. Because of all the folds in the human cerebral cortex, it has a surface area of about 2,500 cm2<\/sup>\u00a0(2.5 ft2<\/sup>). The size and importance of the cerebral cortex is far greater in the human brain than the brains of any other vertebrates, including nonhuman\u00a0primates.<\/p>\n
The Limbic System<\/h3>\n
The limbic system consists of the hypothalamus, thalamus, the hippocampus and amygdala. The structures and interacting areas of the\u00a0limbic system<\/a><\/b>\u00a0are involved in motivation, emotion, learning, and memory.<\/p>\n
Thalamus and Hypothalamus<\/h4>\n
Several structures are located deep within the brain and are important for communication between the brain and spinal cord (or the rest of the body). These structures include the hypothalamus and thalamus. The diagram below (Figure 8.5.7) shows where these structures are located in the brain. Like the two halves of the cerebrum, the hypothalamus and thalamus exist in two halves, one in each hemisphere.<\/p>\n
Figure 8.5.7 Structures deep within the brain include the hypothalamus and thalamus.<\/em><\/figcaption><\/figure>\n The\u00a0hypothalamus<\/a><\/strong>\u00a0is located just above the brain stem, and is about the size of an almond. The hypothalamus is responsible for certain metabolic processes and other activities of the autonomic nervous system<\/a>, including body\u00a0temperature,\u00a0heart\u00a0rate, hunger, thirst, fatigue, sleep, wakefulness, and circadian (24-hour) rhythms. The hypothalamus is also an important emotional center of the brain. The hypothalamus can regulate so many body functions because it responds to many different internal and external signals, including messages from the brain, light, steroid hormones, stress, and invading pathogens, among others.<\/p>\n
One way the hypothalamus influences body functions is by synthesizing hormones that directly influence body processes. It synthesizes the hormone oxytocin<\/a>, which stimulates uterine contractions during childbirth and the letdown of milk during lactation. It also synthesizes antidiuretic hormone<\/a>, which stimulates the kidneys to reabsorb more water and excrete more concentrated urine. These two hormones are sent from the hypothalamus via a stalk-like structure called the infundibulum (see Figure 8.5.7) directly to the posterior (back) portion of the pituitary gland, which secretes them into the blood.<\/p>\n
The main way the hypothalamus influences body functions is by controlling the\u00a0pituitary gland<\/a>, known as the master gland of the\u00a0endocrine system. The hypothalamus synthesizes neurohormones called releasing factors that travel through the infundibulum directly to the anterior (front) part of the pituitary gland. The releasing factors generally either stimulate or inhibit the secretion of anterior pituitary hormones, most of which control other glands of the endocrine system.<\/p>\n
- The\u00a0parietal lobes<\/a><\/strong>\u00a0are located behind the frontal lobes at the top of the head. The parietal lobes are involved in sensation \u2014 including\u00a0temperature, touch, and taste. Reading and arithmetic are also functions of the parietal lobes.<\/li>\n
- The\u00a0frontal lobes<\/a><\/strong>\u00a0are located at the front of the brain behind the forehead. The frontal lobes are associated with executive functions, such as attention, self-control, planning, problem solving, reasoning, abstract thought, language, and personality.<\/li>\n
- The\u00a0[pb_glossary id=\"3088\"]parietal lobes[\/pb_glossary]<\/strong>\u00a0are located behind the frontal lobes at the top of the head. The parietal lobes are involved in sensation \u2014 including\u00a0temperature, touch, and taste. Reading and arithmetic are also functions of the parietal lobes.<\/li>\r\n \t
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