![\"\"](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/Hydrocephalus_CDC-2.png\")
Figure 7.1.2 Comparison of an infant with and without hydrocephalus. The ventricles (shown in blue-gray) are located inside the brain (shown in pink).<\/em>[\/caption]\r\n\r\nHydrocephalus often occurs at birth, as a result of genetic factors or events that occurred during fetal development. Because babies are born with skull bones that are not fully fused, the skull of a baby born with hydrocephalus can expand and relieve some of the pressure on the brain, as reflected in the enlarged head size shown in Figure 7.1.2. Adults have fully fused, inflexible skulls, so when hydrocephalus occurs in an adult, the brain experiences all of the increased pressure.\r\n\r\nWhy did Jayson develop hydrocephalus? There are many possible causes of hydrocephalus in adults, including tumors, infections, hemorrhages, and TBIs. Given his repeated and long history of football-related TBIs and the absence of any evidence of infection, tumor, or other cause, Jayson\u2019s doctor thinks his head injuries were most likely responsible for his hydrocephalus.\r\n\r\nAlthough hydrocephalus is serious, there are treatments. Read the rest of this chapter to learn about the cells, tissues, organs, cavities, and systems of the body, how they are interconnected, and the importance of keeping the body in a state of [pb_glossary id=\"5761\"]homeostasis[\/pb_glossary] (or balance). The amount of cerebrospinal fluid in the ventricles is normally kept at a relatively steady level, and the potentially devastating symptoms of hydrocephalus are an example of what can happen when a system in the body becomes unbalanced. At the end of the chapter, you will learn about Jayson\u2019s treatment and prognosis.\r\nChapter Overview: Introduction to the Human Body<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nIn this chapter, you will learn about the general organization and functions of the human body. Specifically, you will learn about:\r\n\r\n \t- The organization of the body from [pb_glossary id=\"5711\"]atoms[\/pb_glossary] and [pb_glossary id=\"5779\"]molecules[\/pb_glossary] up through [pb_glossary id=\"5665\"]cells[\/pb_glossary], tissues, organs, and organ systems.<\/li>\r\n \t
- How organ systems work together to carry out the functions of life.<\/li>\r\n \t
- The variety of different specialized cell types in humans, the four major types of human tissues, and some of their functions.<\/li>\r\n \t
- The five vital organs and the 11 major organ systems of the human body.<\/li>\r\n \t
- Spaces in the body called body cavities, and the organs they hold and protect.<\/li>\r\n \t
- The tissues and fluid that protect the brain and spinal cord.<\/li>\r\n \t
- How organ systems communicate and interact in body processes, such as cellular respiration, digestion, the fight-or-flight response to stressors, and physical activities (such as sports).<\/li>\r\n \t
- How homeostasis is maintained to keep the body in a relatively steady state, and the problems that can be caused by loss of homeostasis, such as diabetes.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n\r\n\r\nAs you read the chapter, think about the following questions:\r\n
\r\n \t- What is the normal function of cerebrospinal fluid?<\/li>\r\n \t
- What is a spinal tap and how does it test for infection?<\/li>\r\n \t
- In Jayson\u2019s case, what organs and organ systems are probably affected by his hydrocephalus? What are some ways in which these organ systems interact?<\/li>\r\n \t
- The level of cerebrospinal fluid is normally kept in a state of homeostasis. What are other examples of types of homeostasis that keep your body functioning properly?<\/li>\r\n<\/ol>\r\n<\/div>\r\n
Attributions<\/h2>\r\nFigure 7.1.1.<\/strong>\r\n\r\nFootball tackel<\/a> [photo] by John Torcasio<\/a> on Unsplash<\/a> is used under the Unsplash License<\/a> (https:\/\/unsplash.com\/license).\r\n\r\nFigure 7.1.2<\/strong>\r\n\r\nHydrocephalus<\/a>\u00a0by Centers for Disease Control and Prevention (CDC)<\/a> on Wikimedia Commons is in the <\/em><\/i>public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).<\/em><\/i>\r\nReferences<\/h2>\r\n
Mayo Clinic Staff. (n.d.). Hydrocephalus [online article]. MayoClinic.org. https:\/\/www.mayoclinic.org\/diseases-conditions\/hydrocephalus\/symptoms-causes\/syc-20373604<\/p>\r\n
Mayo Clinic Staff. (n.d.). Traumatic brain injury [online article]. MayoClinic.org. https:\/\/www.mayoclinic.org\/diseases-conditions\/traumatic-brain-injury\/symptoms-causes\/syc-20378557<\/p>","rendered":"
<\/p>\n![\"\"](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2019\/06\/Football-tackel-by-john-torcasio-P2rqmExt74A-unsplash-scaled-3.jpg\")
Figure 7.1.1 Football often involves forceful impact to the head which makes wearing a helmet critical.<\/em><\/figcaption><\/figure>\nLooking at this photo of a football game (Figure 7.1.1), you can see why it is so important that the players wear helmets. As players tackle each other, football often involves forceful impact to the head. This can cause damage to the brain \u2014 temporarily (as in the case of a concussion) or long-term and more severe. Helmets are critical in reducing the incidence of traumatic brain injuries<\/a> (TBIs<\/a>), but they do not fully prevent them.<\/p>\nAs a former professional football player who also played in college and high school, 43-year-old Jayson sustained many high-impact head injuries over the course of his football playing years. A few years ago, Jayson began experiencing a variety of troubling symptoms, including the loss of bladder control (the involuntary leakage of urine), memory loss, and difficulty walking. Symptoms like these are often signs of damage to the nervous system, which includes the brain, spinal cord, and nerves, but they can result from many different types of injuries or diseases that affect the nervous system. In order to treat him properly, Jayson\u2019s doctors needed to do several tests to determine the exact cause of his symptoms. The doctors ordered a spinal tap to see if he had an infection, and an MRI (magnetic resonance imaging) to see if there were any observable problems in and around his brain.<\/p>\n
The MRI revealed the cause of Jayson\u2019s symptoms. There are fluid-filled spaces within the brain called ventricles, and compared to normal ventricles, Jayson\u2019s ventricles were enlarged. Based on this observation, along with the results of other tests, Jayson\u2019s doctor diagnosed him with hydrocephalus<\/a>, a term that literally means \u201cwater head.\u201d Hydrocephalus<\/a> occurs when the fluid that fills the ventricles \u2014 called cerebrospinal fluid \u2014 builds up excessively, causing the ventricles to become enlarged. This puts pressure on the brain, which can cause a variety of neurological symptoms, including the ones Jayson was experiencing. In Figure 7.1.2, you can see the difference between normal ventricles and ventricles that are enlarged due to hydrocephalus. Notice in the image on the right how the brain becomes \u201csqueezed\u201d due to hydrocephalus.<\/p>\nFigure 7.1.2 Comparison of an infant with and without hydrocephalus. The ventricles (shown in blue-gray) are located inside the brain (shown in pink).<\/em><\/figcaption><\/figure>\nHydrocephalus often occurs at birth, as a result of genetic factors or events that occurred during fetal development. Because babies are born with skull bones that are not fully fused, the skull of a baby born with hydrocephalus can expand and relieve some of the pressure on the brain, as reflected in the enlarged head size shown in Figure 7.1.2. Adults have fully fused, inflexible skulls, so when hydrocephalus occurs in an adult, the brain experiences all of the increased pressure.<\/p>\n
Why did Jayson develop hydrocephalus? There are many possible causes of hydrocephalus in adults, including tumors, infections, hemorrhages, and TBIs. Given his repeated and long history of football-related TBIs and the absence of any evidence of infection, tumor, or other cause, Jayson\u2019s doctor thinks his head injuries were most likely responsible for his hydrocephalus.<\/p>\n
Although hydrocephalus is serious, there are treatments. Read the rest of this chapter to learn about the cells, tissues, organs, cavities, and systems of the body, how they are interconnected, and the importance of keeping the body in a state of homeostasis<\/a> (or balance). The amount of cerebrospinal fluid in the ventricles is normally kept at a relatively steady level, and the potentially devastating symptoms of hydrocephalus are an example of what can happen when a system in the body becomes unbalanced. At the end of the chapter, you will learn about Jayson\u2019s treatment and prognosis.<\/p>\n\n\nChapter Overview: Introduction to the Human Body<\/span><\/h1>\n<\/header>\n\nIn this chapter, you will learn about the general organization and functions of the human body. Specifically, you will learn about:<\/p>\n
\n- The organization of the body from atoms<\/a> and molecules<\/a> up through cells<\/a>, tissues, organs, and organ systems.<\/li>\n
- How organ systems work together to carry out the functions of life.<\/li>\n
- The variety of different specialized cell types in humans, the four major types of human tissues, and some of their functions.<\/li>\n
- The five vital organs and the 11 major organ systems of the human body.<\/li>\n
- Spaces in the body called body cavities, and the organs they hold and protect.<\/li>\n
- The tissues and fluid that protect the brain and spinal cord.<\/li>\n
- How organ systems communicate and interact in body processes, such as cellular respiration, digestion, the fight-or-flight response to stressors, and physical activities (such as sports).<\/li>\n
- How homeostasis is maintained to keep the body in a relatively steady state, and the problems that can be caused by loss of homeostasis, such as diabetes.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n
As you read the chapter, think about the following questions:<\/p>\n
\n- What is the normal function of cerebrospinal fluid?<\/li>\n
- What is a spinal tap and how does it test for infection?<\/li>\n
- In Jayson\u2019s case, what organs and organ systems are probably affected by his hydrocephalus? What are some ways in which these organ systems interact?<\/li>\n
- The level of cerebrospinal fluid is normally kept in a state of homeostasis. What are other examples of types of homeostasis that keep your body functioning properly?<\/li>\n<\/ol>\n<\/div>\n
Attributions<\/h2>\n
Figure 7.1.1.<\/strong><\/p>\nFootball tackel<\/a> [photo] by John Torcasio<\/a> on Unsplash<\/a> is used under the Unsplash License<\/a> (https:\/\/unsplash.com\/license).<\/p>\nFigure 7.1.2<\/strong><\/p>\nHydrocephalus<\/a>\u00a0by Centers for Disease Control and Prevention (CDC)<\/a> on Wikimedia Commons is in the <\/em><\/i>public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).<\/em><\/i><\/p>\nReferences<\/h2>\n
Mayo Clinic Staff. (n.d.). Hydrocephalus [online article]. MayoClinic.org. https:\/\/www.mayoclinic.org\/diseases-conditions\/hydrocephalus\/symptoms-causes\/syc-20373604<\/p>\n
Mayo Clinic Staff. (n.d.). Traumatic brain injury [online article]. MayoClinic.org. https:\/\/www.mayoclinic.org\/diseases-conditions\/traumatic-brain-injury\/symptoms-causes\/syc-20378557<\/p>\n
definition<\/span>Created by CK-12 Foundation\/Adapted by Christine Miller<\/p>\n![\"\"](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2019\/06\/Nest_Thermostat.jpg\")
Figure 7.8.1\u00a0 A thermostat controls a complex system to maintain a steady temperature in our homes.\u00a0<\/em><\/figcaption><\/figure>\nSteady as She Goes<\/h1>\n
This device (Figure 7.8.1) looks simple, but it controls a complex system that keeps a home at a steady temperature \u2014 it's a thermostat. The device shows the current temperature in the room, and also allows the occupant to set the thermostat to the desired temperature. A thermostat is a commonly cited model of how living systems \u2014 including the human body\u2014 maintain a steady state called homeostasis.<\/p>\n
\nWhat Is Homeostasis?<\/h1>\n<\/div>\n
Homeostasis<\/a><\/strong>\u00a0is the condition in which a system (such as the human body) is maintained in a more or less steady state. It is the job of\u00a0cells<\/a>, tissues<\/a>, organs<\/a>, and organ systems<\/a>\u00a0throughout the body to maintain many different variables within narrow ranges compatible with life. Keeping a stable internal environment requires continually monitoring the internal environment and constantly making adjustments to keep things in balance.<\/p>\nSet Point and Normal Range<\/h2>\n
For any given variable, such as body\u00a0temperature\u00a0or\u00a0blood\u00a0glucose level, there is a particular\u00a0set point<\/a><\/strong>\u00a0that is the physiological optimum value.\u00a0The set point for\u00a0human body\u00a0temperature, for example, is about 37 degrees C (98.6 degrees F). As the body works to maintain homeostasis<\/a> for temperature or any other internal variable, the value typically fluctuates around the set point. Such fluctuations are normal, as long as they do not become too extreme. The spread of values within which such fluctuations are considered insignificant is called the\u00a0normal range<\/a><\/strong>. In the case of body temperature, for example, the normal range for an adult is about 36.5 to 37.5 degrees C (97.7 to 99.5 degrees F).<\/p>\nA good analogy for set point, normal range, and maintenance of homeostasis is driving.\u00a0 When you are driving a vehicle on the road, you are supposed to drive in the centre of your lane \u2014 this is analogous to the set point<\/a>.\u00a0 Sometimes, you are not driving in the exact<\/em> centre of the lane, but you are still within your lines, so you are in the equivalent of the normal range<\/a>.\u00a0 However, if you were to get too close to the centre line or the shoulder of the road, you would take action to correct your position.\u00a0 You'd move left if you were too close to the shoulder, or right if too close to the centre line \u2014 which is analogous to our next concept, negative feedback<\/a> to maintain homeostasis<\/a>.<\/p>\nMaintaining Homeostasis<\/h2>\n
Homeostasis<\/a> is normally maintained in the human body by an extremely complex balancing act. Regardless of the variable being kept within its normal range, maintaining homeostasis requires at least four interacting components: stimulus, sensor, control centre, and effector.<\/p>\n\n- The\u00a0stimulus<\/a><\/strong>\u00a0is provided by the variable being regulated. Generally, the stimulus indicates that the value of the variable has moved away from the set point or has left the normal range.<\/li>\n
- The\u00a0sensor<\/a><\/strong> monitors the values of the variable and sends data on it to the control centre.<\/li>\n
- The\u00a0control centre<\/a><\/strong> matches the data with normal values. If the value is not at the set point or is outside the normal range, the control centre sends a signal to the effector.<\/li>\n
- The\u00a0effector<\/a><\/strong> is an organ, gland, muscle, or other structure that acts on the signal from the control centre to move the variable back toward the set point.<\/li>\n<\/ol>\n
Each of these components is illustrated in Figure 7.8.2. The diagram on the left is a general model showing how the components interact to maintain homeostasis. The diagram on the right shows the example of body temperature. From the diagrams, you can see that maintaining homeostasis involves feedback, which is data that feeds back to control a response. Feedback may be negative (as in the example below) or positive. All the feedback mechanisms that maintain homeostasis use negative feedback<\/a>. Biological examples of positive feedback are much less common.<\/p>\n <\/p>\n
<\/p>\n![\"\"](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/Negative_Feedback_Loops.jpg\")
Figure 7.8.2 Maintaining homeostasis through feedback requires a stimulus, sensor, control centre, and effector.<\/em><\/figcaption><\/figure>\n\nNegative Feedback<\/span><\/p>\n<\/div>\nIn a\u00a0negative feedback loop<\/a><\/strong>, feedback serves to reduce an excessive response and keep a variable within the normal range<\/a>.\u00a0Two\u00a0processes controlled by negative feedback\u00a0are\u00a0body temperature regulation and control of\u00a0blood\u00a0glucose.<\/p>\nBody Temperature<\/h2>\n
Body temperature regulation involves negative feedback<\/a>, whether it lowers the temperature or raises it, as shown in Figure 7.8.3 and explained in the text that follows.<\/p>\n![\"Homeostasis](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/Body-Temperature-Homeostasis.jpg\")
Figure 7.8.3 Homeostasis of body temperature is maintained by negative feedback loops.<\/em><\/figcaption><\/figure>\n\nCooling Down<\/span><\/p>\n<\/div>\nThe human body\u2019s temperature regulatory centre is the hypothalamus<\/a> in the brain. When the hypothalamus receives data from sensors in the skin and brain that body temperature is higher than the set point<\/a>, it sets into motion the following responses:<\/p>\n\n- Blood vessels\u00a0in the skin dilate (vasodilation) to allow more\u00a0blood\u00a0from the warm body core to flow close to the surface of the body, so\u00a0heat can be radiated into\u00a0the environment.<\/li>\n
- As blood flow to the skin increases, sweat glands in the skin are activated to increase their output of sweat (diaphoresis). When the sweat evaporates from the skin surface into the surrounding air, it takes\u00a0heat\u00a0with it.<\/li>\n
- Breathing\u00a0becomes deeper, and the person may breathe through the mouth instead of the nasal passages. This increases\u00a0heat\u00a0loss from the lungs.<\/li>\n<\/ul>\n
Heating Up<\/h3>\n
When the brain\u2019s temperature regulatory centre receives data that body temperature is lower than the set point, it sets into motion the following responses:<\/p>\n
\n- Blood vessels\u00a0in the skin contract (vasoconstriction) to prevent blood from flowing close to the surface of the body, which reduces heat loss from the surface.<\/li>\n
- As temperature falls lower, random signals to\u00a0skeletal muscles\u00a0are triggered, causing them to contract. This causes shivering, which generates a small amount of heat.<\/li>\n
- The\u00a0thyroid gland<\/a>\u00a0may be stimulated by the brain (via the pituitary gland) to secrete more thyroid\u00a0hormone. This hormone increases metabolic activity and heat production in\u00a0cells\u00a0throughout the body.<\/li>\n
- The\u00a0adrenal glands<\/a>\u00a0may also be stimulated to secrete the\u00a0hormone adrenaline<\/a>. This hormone causes the breakdown of glycogen (the\u00a0carbohydrate\u00a0used for\u00a0energy\u00a0storage in animals) to glucose<\/a>, which can be used as an energy source. This catabolic chemical process is exothermic<\/a>, or heat producing.<\/li>\n<\/ul>\n
Blood Glucose<\/h2>\n
In controlling\u00a0the blood glucose level, certain endocrine\u00a0cells\u00a0in the\u00a0pancreas\u00a0(called alpha and beta cells) detect the level of glucose in the blood. They then respond appropriately to keep the level of blood glucose within the normal range.<\/p>\n
\n- If the blood glucose level rises above the normal range, pancreatic beta cells release the\u00a0hormone\u00a0insulin into the bloodstream. Insulin signals cells to take up the excess glucose from the blood until the level of blood glucose decreases to the normal range.<\/li>\n
- If the blood glucose level falls below the normal range, pancreatic alpha cells release the hormone\u00a0glucagon<\/strong>\u00a0into the bloodstream. Glucagon signals cells to break down stored glycogen to glucose and release the glucose into the blood until the level of blood glucose increases to the normal range.<\/li>\n<\/ul>\n\n
<\/p>\n![\"Diagram](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/Homeostasis_of_blood_sugar.png\")
Figure 7.8.4 Your liver plays an important role in balancing blood sugar levels. Glycogen in your liver can either collect glucose out of your blood stream to lower blood sugar, or release glucose into the bloodstream to increase blood sugar.\u00a0 This happens through a negative feedback loop.<\/em><\/figcaption><\/figure>\n <\/p>\n
https:\/\/www.youtube.com\/watch?v=Iz0Q9nTZCw4<\/p>\n
Homeostasis and Negative\/Positive Feedback, Amoeba Sisters, 2017.<\/p>\n
Positive Feedback<\/h1>\n<\/div>\n
In a\u00a0positive feedback loop<\/a><\/strong>, feedback serves to intensify a response until an end point is reached. Examples of processes controlled by positive feedback in the human body include blood clotting and childbirth.<\/p>\nBlood Clotting<\/h2>\n![\"Positive](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/Positive_Feedback_Diagram_Blood_Clotting.png\")
Figure 7.8.5 The diagram demonstrates positive feedback, using the example of blood clotting in the body. The damaged blood vessel wall releases chemicals that initiate the formation of a blood clot. Every time the blood clot builds up more, more chemicals are released that speed up the process. The process gets faster and faster until the blood vessel wall is completely healed and the positive feedback loop has ended. The graph represents the number of platelets aiding in the formation of the blood clot. The exponential form of the graph represents the positive feedback mechanism.<\/em><\/figcaption><\/figure>\nWhen a wound causes bleeding, the body responds with a positive feedback loop to clot the blood and stop blood loss. Substances released by the injured blood vessel wall begin the process of blood clotting. Platelets in the blood start to cling to the injured site and release chemicals that attract additional platelets. As the platelets continue to amass, more of the chemicals are released and more platelets are attracted to the site of the clot. The positive feedback accelerates the process of clotting until the clot is large enough to stop the bleeding.<\/p>\n
Childbirth<\/h2>\n
Figure 7.8.6 shows the positive feedback loop that controls childbirth. The process normally begins when the head of the infant pushes against the cervix. This stimulates nerve impulses, which travel from the cervix to the hypothalamus in the brain. In response, the hypothalamus sends the hormone oxytocin<\/a><\/strong>\u00a0to the\u00a0pituitary gland,\u00a0which secretes it into the bloodstream so it can be carried to the uterus. Oxytocin stimulates uterine contractions, which push the baby harder against the cervix. In response, the cervix starts to dilate in preparation for the passage of the baby. This cycle of positive feedback continues, with increasing levels of oxytocin, stronger uterine contractions, and wider dilation of the cervix until the baby is pushed through the birth canal and out of the body. At that point, the cervix is no longer stimulated to send\u00a0nerve impulses\u00a0to the brain, and the entire process stops.<\/p>\n![\"Positive](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/Pregnancy-Positive_Feedback.jpg\")
Figure 7.8.6 Normal childbirth is driven by a positive feedback loop.\u00a0<\/em><\/figcaption><\/figure>\n\nNormal childbirth is driven by a positive feedback loop. Positive feedback causes an increasing deviation from the normal state to a fixed end point, rather than a return to a normal set point as in homeostasis.<\/p>\n<\/div>\n
\nWhen Homeostasis Fails<\/h1>\n<\/div>\n
Homeostatic mechanisms work continuously to maintain stable conditions in the human body. Sometimes, however, the mechanisms fail. When they do,\u00a0homeostatic imbalance<\/a><\/strong>\u00a0may result, in which cells may not get everything they need or toxic wastes may accumulate in the body. If homeostasis is not restored, the imbalance may lead to disease \u2014 or even death.\u00a0Diabetes<\/a>\u00a0is an example of a disease caused by homeostatic imbalance. In the case of diabetes, blood glucose levels are no longer regulated and may be dangerously high. Medical intervention can help restore homeostasis and possibly prevent permanent damage to the organism.<\/p>\nNormal aging may bring about a reduction in the\u00a0efficiency\u00a0of the body\u2019s control systems, which makes the body more susceptible to disease.\u00a0Older people, for example, may have a harder time regulating their body temperature. This is one reason they are more likely than younger people to develop serious heat-induced illnesses, such as heat stroke.<\/p>\n
\nFeature: My Human Body<\/h1>\n<\/div>\n
Diabetes<\/a>\u00a0is diagnosed in people who have abnormally high levels of blood glucose after fasting for at least 12 hours. A fasting level of blood glucose below 100 is normal. A level between 100 and 125 places you in the pre-diabetes category, and a level higher than 125 results in a diagnosis of diabetes.<\/p>\nOf the two types of diabetes, type 2 diabetes<\/a> is the most common, accounting for about 90 per cent of all cases of diabetes in the United States. Type 2 diabetes<\/a> typically starts after the age of 40. However, because of the dramatic increase in recent decades in obesity in younger people, the age at which type 2 diabetes is diagnosed has fallen. Even children are now being diagnosed with type 2 diabetes. Today, about 3 million Canadians (8.1% of total population) are living with diabetes.<\/p>\nYou may at some point have your blood glucose level tested during a routine medical exam. If your blood glucose level indicates that you have diabetes, it may come as a shock to you because you may not have any symptoms of the disease. You are not alone, because as many as one in four diabetics do not know they have the disease. Once the diagnosis of diabetes sinks in, you may be devastated by the news. Diabetes can lead to heart attacks, strokes, blindness, kidney failure, nerve damage, and loss of toes or feet. The risk of death in adults with diabetes is 50 per cent greater than it is in adults without diabetes, and diabetes is the seventh leading cause of death of adults. In addition, controlling diabetes usually requires frequent blood glucose testing, watching what and when you eat, and taking medications or even insulin injections. All of this may seem overwhelming.<\/p>\n
The good news is that changing your lifestyle may stop the progression of type 2 diabetes or even reverse it. By adopting healthier habits, you may be able to keep your blood glucose level within the normal range without medications or insulin. Here\u2019s how:<\/p>\n
\n- Lose\u00a0weight.<\/strong> Any\u00a0weight\u00a0loss is beneficial. Losing as little as\u00a0seven\u00a0per cent of your\u00a0weight\u00a0may be all that is needed to stop diabetes in its tracks. It is especially important to eliminate excess weight around your waist.<\/li>\n
- Exercise\u00a0regularly.<\/strong>\u00a0You should try to\u00a0exercise\u00a0for at least 30 minutes, five days a week. This will not only lower your blood sugar and help your insulin work better, but it will also lower your\u00a0blood pressure\u00a0and improve your\u00a0heart\u00a0health. Another bonus of exercise is that it will help you lose weight by increasing your basal metabolic rate.<\/li>\n
- Adopt a healthy diet.<\/strong> Decrease your consumption of refined carbohydrates, such as sweets and sugary drinks. Increase your intake of fibre-rich foods, such as fruits, vegetables, and whole grains. About one-quarter of each meal should consist of high-protein foods, such as fish, chicken, dairy products, legumes, or nuts.<\/li>\n
- Control stress.<\/strong>\u00a0Stress can increase your blood glucose and also raise your\u00a0blood pressure\u00a0and risk of\u00a0heart\u00a0disease. When you feel stressed out, do\u00a0breathing\u00a0exercises or take a brisk walk or jog.\u00a0Try to replace stressful thoughts with more calming ones.<\/li>\n
- Establish a support system.<\/strong>\u00a0Enlist the help and support of loved ones, as well as medical professionals, such as a nutritionist and diabetes educator. Having a support system will help ensure that you are on the path to wellness, and that you can stick to your plan.<\/li>\n<\/ul>\n\n\n
\n7.8 Summary<\/span><\/h1>\n<\/header>\n\n\n- Homeostasis<\/a> is the condition in which a system (such as the human body) is maintained in a more or less steady state. It is the job of cells, tissues, organs, and organ systems throughout the body to maintain homeostasis.<\/li>\n
- For any given variable, such as body temperature, there is a particular set point<\/a> that is the physiological optimum value. The spread of values around the set point that is considered insignificant is called the normal range<\/a>.<\/li>\n
- Homeostasis is generally maintained by a negative feedback loop<\/a> that includes a stimulus<\/a>, sensor<\/a>, control centre<\/a>, and effector<\/a>. Negative feedback serves to reduce an excessive response and to keep a variable within the normal range. Negative feedback loops control body temperature and the blood glucose level.<\/li>\n
- Positive feedback loops<\/a>\u00a0are not common in biological systems. Positive feedback serves to intensify a response until an end point is reached. Positive feedback loops control blood clotting and childbirth.<\/li>\n
- Sometimes homeostatic mechanisms fail, resulting in homeostatic imbalance<\/a>. Diabetes is an example of a disease caused by homeostatic imbalance. Aging can bring about a reduction in the\u00a0efficiency\u00a0of the body\u2019s control system,\u00a0which makes\u00a0the elderly more susceptible to disease.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n
\n7.8 Review Questions<\/span><\/h1>\n<\/header>\n\n\n- \n\n
- \r\n \t
- The organization of the body from [pb_glossary id=\"5711\"]atoms[\/pb_glossary] and [pb_glossary id=\"5779\"]molecules[\/pb_glossary] up through [pb_glossary id=\"5665\"]cells[\/pb_glossary], tissues, organs, and organ systems.<\/li>\r\n \t
- How organ systems work together to carry out the functions of life.<\/li>\r\n \t
- The variety of different specialized cell types in humans, the four major types of human tissues, and some of their functions.<\/li>\r\n \t
- The five vital organs and the 11 major organ systems of the human body.<\/li>\r\n \t
- Spaces in the body called body cavities, and the organs they hold and protect.<\/li>\r\n \t
- The tissues and fluid that protect the brain and spinal cord.<\/li>\r\n \t
- How organ systems communicate and interact in body processes, such as cellular respiration, digestion, the fight-or-flight response to stressors, and physical activities (such as sports).<\/li>\r\n \t
- How homeostasis is maintained to keep the body in a relatively steady state, and the problems that can be caused by loss of homeostasis, such as diabetes.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n\r\n\r\nAs you read the chapter, think about the following questions:\r\n
- \r\n \t
- What is the normal function of cerebrospinal fluid?<\/li>\r\n \t
- What is a spinal tap and how does it test for infection?<\/li>\r\n \t
- In Jayson\u2019s case, what organs and organ systems are probably affected by his hydrocephalus? What are some ways in which these organ systems interact?<\/li>\r\n \t
- The level of cerebrospinal fluid is normally kept in a state of homeostasis. What are other examples of types of homeostasis that keep your body functioning properly?<\/li>\r\n<\/ol>\r\n<\/div>\r\n
Attributions<\/h2>\r\nFigure 7.1.1.<\/strong>\r\n\r\nFootball tackel<\/a> [photo] by John Torcasio<\/a> on Unsplash<\/a> is used under the Unsplash License<\/a> (https:\/\/unsplash.com\/license).\r\n\r\nFigure 7.1.2<\/strong>\r\n\r\nHydrocephalus<\/a>\u00a0by Centers for Disease Control and Prevention (CDC)<\/a> on Wikimedia Commons is in the <\/em><\/i>public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).<\/em><\/i>\r\n
References<\/h2>\r\n
Mayo Clinic Staff. (n.d.). Hydrocephalus [online article]. MayoClinic.org. https:\/\/www.mayoclinic.org\/diseases-conditions\/hydrocephalus\/symptoms-causes\/syc-20373604<\/p>\r\n
Mayo Clinic Staff. (n.d.). Traumatic brain injury [online article]. MayoClinic.org. https:\/\/www.mayoclinic.org\/diseases-conditions\/traumatic-brain-injury\/symptoms-causes\/syc-20378557<\/p>","rendered":"
<\/p>\n
Figure 7.1.1 Football often involves forceful impact to the head which makes wearing a helmet critical.<\/em><\/figcaption><\/figure>\n Looking at this photo of a football game (Figure 7.1.1), you can see why it is so important that the players wear helmets. As players tackle each other, football often involves forceful impact to the head. This can cause damage to the brain \u2014 temporarily (as in the case of a concussion) or long-term and more severe. Helmets are critical in reducing the incidence of traumatic brain injuries<\/a> (TBIs<\/a>), but they do not fully prevent them.<\/p>\n
As a former professional football player who also played in college and high school, 43-year-old Jayson sustained many high-impact head injuries over the course of his football playing years. A few years ago, Jayson began experiencing a variety of troubling symptoms, including the loss of bladder control (the involuntary leakage of urine), memory loss, and difficulty walking. Symptoms like these are often signs of damage to the nervous system, which includes the brain, spinal cord, and nerves, but they can result from many different types of injuries or diseases that affect the nervous system. In order to treat him properly, Jayson\u2019s doctors needed to do several tests to determine the exact cause of his symptoms. The doctors ordered a spinal tap to see if he had an infection, and an MRI (magnetic resonance imaging) to see if there were any observable problems in and around his brain.<\/p>\n
The MRI revealed the cause of Jayson\u2019s symptoms. There are fluid-filled spaces within the brain called ventricles, and compared to normal ventricles, Jayson\u2019s ventricles were enlarged. Based on this observation, along with the results of other tests, Jayson\u2019s doctor diagnosed him with hydrocephalus<\/a>, a term that literally means \u201cwater head.\u201d Hydrocephalus<\/a> occurs when the fluid that fills the ventricles \u2014 called cerebrospinal fluid \u2014 builds up excessively, causing the ventricles to become enlarged. This puts pressure on the brain, which can cause a variety of neurological symptoms, including the ones Jayson was experiencing. In Figure 7.1.2, you can see the difference between normal ventricles and ventricles that are enlarged due to hydrocephalus. Notice in the image on the right how the brain becomes \u201csqueezed\u201d due to hydrocephalus.<\/p>\n
Figure 7.1.2 Comparison of an infant with and without hydrocephalus. The ventricles (shown in blue-gray) are located inside the brain (shown in pink).<\/em><\/figcaption><\/figure>\n Hydrocephalus often occurs at birth, as a result of genetic factors or events that occurred during fetal development. Because babies are born with skull bones that are not fully fused, the skull of a baby born with hydrocephalus can expand and relieve some of the pressure on the brain, as reflected in the enlarged head size shown in Figure 7.1.2. Adults have fully fused, inflexible skulls, so when hydrocephalus occurs in an adult, the brain experiences all of the increased pressure.<\/p>\n
Why did Jayson develop hydrocephalus? There are many possible causes of hydrocephalus in adults, including tumors, infections, hemorrhages, and TBIs. Given his repeated and long history of football-related TBIs and the absence of any evidence of infection, tumor, or other cause, Jayson\u2019s doctor thinks his head injuries were most likely responsible for his hydrocephalus.<\/p>\n
Although hydrocephalus is serious, there are treatments. Read the rest of this chapter to learn about the cells, tissues, organs, cavities, and systems of the body, how they are interconnected, and the importance of keeping the body in a state of homeostasis<\/a> (or balance). The amount of cerebrospinal fluid in the ventricles is normally kept at a relatively steady level, and the potentially devastating symptoms of hydrocephalus are an example of what can happen when a system in the body becomes unbalanced. At the end of the chapter, you will learn about Jayson\u2019s treatment and prognosis.<\/p>\n
\n\n Chapter Overview: Introduction to the Human Body<\/span><\/h1>\n<\/header>\n
\nIn this chapter, you will learn about the general organization and functions of the human body. Specifically, you will learn about:<\/p>\n
- \n
- The organization of the body from atoms<\/a> and molecules<\/a> up through cells<\/a>, tissues, organs, and organ systems.<\/li>\n
- How organ systems work together to carry out the functions of life.<\/li>\n
- The variety of different specialized cell types in humans, the four major types of human tissues, and some of their functions.<\/li>\n
- The five vital organs and the 11 major organ systems of the human body.<\/li>\n
- Spaces in the body called body cavities, and the organs they hold and protect.<\/li>\n
- The tissues and fluid that protect the brain and spinal cord.<\/li>\n
- How organ systems communicate and interact in body processes, such as cellular respiration, digestion, the fight-or-flight response to stressors, and physical activities (such as sports).<\/li>\n
- How homeostasis is maintained to keep the body in a relatively steady state, and the problems that can be caused by loss of homeostasis, such as diabetes.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n
\nAs you read the chapter, think about the following questions:<\/p>\n
- \n
- What is the normal function of cerebrospinal fluid?<\/li>\n
- What is a spinal tap and how does it test for infection?<\/li>\n
- In Jayson\u2019s case, what organs and organ systems are probably affected by his hydrocephalus? What are some ways in which these organ systems interact?<\/li>\n
- The level of cerebrospinal fluid is normally kept in a state of homeostasis. What are other examples of types of homeostasis that keep your body functioning properly?<\/li>\n<\/ol>\n<\/div>\n
Attributions<\/h2>\n
Figure 7.1.1.<\/strong><\/p>\n
Football tackel<\/a> [photo] by John Torcasio<\/a> on Unsplash<\/a> is used under the Unsplash License<\/a> (https:\/\/unsplash.com\/license).<\/p>\n
Figure 7.1.2<\/strong><\/p>\n
Hydrocephalus<\/a>\u00a0by Centers for Disease Control and Prevention (CDC)<\/a> on Wikimedia Commons is in the <\/em><\/i>public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain).<\/em><\/i><\/p>\n
References<\/h2>\n
Mayo Clinic Staff. (n.d.). Hydrocephalus [online article]. MayoClinic.org. https:\/\/www.mayoclinic.org\/diseases-conditions\/hydrocephalus\/symptoms-causes\/syc-20373604<\/p>\n
Mayo Clinic Staff. (n.d.). Traumatic brain injury [online article]. MayoClinic.org. https:\/\/www.mayoclinic.org\/diseases-conditions\/traumatic-brain-injury\/symptoms-causes\/syc-20378557<\/p>\n
definition<\/span>Created by CK-12 Foundation\/Adapted by Christine Miller<\/p>\n
Figure 7.8.1\u00a0 A thermostat controls a complex system to maintain a steady temperature in our homes.\u00a0<\/em><\/figcaption><\/figure>\n Steady as She Goes<\/h1>\n
This device (Figure 7.8.1) looks simple, but it controls a complex system that keeps a home at a steady temperature \u2014 it's a thermostat. The device shows the current temperature in the room, and also allows the occupant to set the thermostat to the desired temperature. A thermostat is a commonly cited model of how living systems \u2014 including the human body\u2014 maintain a steady state called homeostasis.<\/p>\n
\nWhat Is Homeostasis?<\/h1>\n<\/div>\n
Homeostasis<\/a><\/strong>\u00a0is the condition in which a system (such as the human body) is maintained in a more or less steady state. It is the job of\u00a0cells<\/a>, tissues<\/a>, organs<\/a>, and organ systems<\/a>\u00a0throughout the body to maintain many different variables within narrow ranges compatible with life. Keeping a stable internal environment requires continually monitoring the internal environment and constantly making adjustments to keep things in balance.<\/p>\n
Set Point and Normal Range<\/h2>\n
For any given variable, such as body\u00a0temperature\u00a0or\u00a0blood\u00a0glucose level, there is a particular\u00a0set point<\/a><\/strong>\u00a0that is the physiological optimum value.\u00a0The set point for\u00a0human body\u00a0temperature, for example, is about 37 degrees C (98.6 degrees F). As the body works to maintain homeostasis<\/a> for temperature or any other internal variable, the value typically fluctuates around the set point. Such fluctuations are normal, as long as they do not become too extreme. The spread of values within which such fluctuations are considered insignificant is called the\u00a0normal range<\/a><\/strong>. In the case of body temperature, for example, the normal range for an adult is about 36.5 to 37.5 degrees C (97.7 to 99.5 degrees F).<\/p>\n
A good analogy for set point, normal range, and maintenance of homeostasis is driving.\u00a0 When you are driving a vehicle on the road, you are supposed to drive in the centre of your lane \u2014 this is analogous to the set point<\/a>.\u00a0 Sometimes, you are not driving in the exact<\/em> centre of the lane, but you are still within your lines, so you are in the equivalent of the normal range<\/a>.\u00a0 However, if you were to get too close to the centre line or the shoulder of the road, you would take action to correct your position.\u00a0 You'd move left if you were too close to the shoulder, or right if too close to the centre line \u2014 which is analogous to our next concept, negative feedback<\/a> to maintain homeostasis<\/a>.<\/p>\n
Maintaining Homeostasis<\/h2>\n
Homeostasis<\/a> is normally maintained in the human body by an extremely complex balancing act. Regardless of the variable being kept within its normal range, maintaining homeostasis requires at least four interacting components: stimulus, sensor, control centre, and effector.<\/p>\n
- \n
- The\u00a0stimulus<\/a><\/strong>\u00a0is provided by the variable being regulated. Generally, the stimulus indicates that the value of the variable has moved away from the set point or has left the normal range.<\/li>\n
- The\u00a0sensor<\/a><\/strong> monitors the values of the variable and sends data on it to the control centre.<\/li>\n
- The\u00a0control centre<\/a><\/strong> matches the data with normal values. If the value is not at the set point or is outside the normal range, the control centre sends a signal to the effector.<\/li>\n
- The\u00a0effector<\/a><\/strong> is an organ, gland, muscle, or other structure that acts on the signal from the control centre to move the variable back toward the set point.<\/li>\n<\/ol>\n
Each of these components is illustrated in Figure 7.8.2. The diagram on the left is a general model showing how the components interact to maintain homeostasis. The diagram on the right shows the example of body temperature. From the diagrams, you can see that maintaining homeostasis involves feedback, which is data that feeds back to control a response. Feedback may be negative (as in the example below) or positive. All the feedback mechanisms that maintain homeostasis use negative feedback<\/a>. Biological examples of positive feedback are much less common.<\/p>\n
<\/p>\n
<\/p>\n
Figure 7.8.2 Maintaining homeostasis through feedback requires a stimulus, sensor, control centre, and effector.<\/em><\/figcaption><\/figure>\n \nNegative Feedback<\/span><\/p>\n<\/div>\n
In a\u00a0negative feedback loop<\/a><\/strong>, feedback serves to reduce an excessive response and keep a variable within the normal range<\/a>.\u00a0Two\u00a0processes controlled by negative feedback\u00a0are\u00a0body temperature regulation and control of\u00a0blood\u00a0glucose.<\/p>\n
Body Temperature<\/h2>\n
Body temperature regulation involves negative feedback<\/a>, whether it lowers the temperature or raises it, as shown in Figure 7.8.3 and explained in the text that follows.<\/p>\n
Figure 7.8.3 Homeostasis of body temperature is maintained by negative feedback loops.<\/em><\/figcaption><\/figure>\n \nCooling Down<\/span><\/p>\n<\/div>\n
The human body\u2019s temperature regulatory centre is the hypothalamus<\/a> in the brain. When the hypothalamus receives data from sensors in the skin and brain that body temperature is higher than the set point<\/a>, it sets into motion the following responses:<\/p>\n
- \n
- Blood vessels\u00a0in the skin dilate (vasodilation) to allow more\u00a0blood\u00a0from the warm body core to flow close to the surface of the body, so\u00a0heat can be radiated into\u00a0the environment.<\/li>\n
- As blood flow to the skin increases, sweat glands in the skin are activated to increase their output of sweat (diaphoresis). When the sweat evaporates from the skin surface into the surrounding air, it takes\u00a0heat\u00a0with it.<\/li>\n
- Breathing\u00a0becomes deeper, and the person may breathe through the mouth instead of the nasal passages. This increases\u00a0heat\u00a0loss from the lungs.<\/li>\n<\/ul>\n
Heating Up<\/h3>\n
When the brain\u2019s temperature regulatory centre receives data that body temperature is lower than the set point, it sets into motion the following responses:<\/p>\n
- \n
- Blood vessels\u00a0in the skin contract (vasoconstriction) to prevent blood from flowing close to the surface of the body, which reduces heat loss from the surface.<\/li>\n
- As temperature falls lower, random signals to\u00a0skeletal muscles\u00a0are triggered, causing them to contract. This causes shivering, which generates a small amount of heat.<\/li>\n
- The\u00a0thyroid gland<\/a>\u00a0may be stimulated by the brain (via the pituitary gland) to secrete more thyroid\u00a0hormone. This hormone increases metabolic activity and heat production in\u00a0cells\u00a0throughout the body.<\/li>\n
- The\u00a0adrenal glands<\/a>\u00a0may also be stimulated to secrete the\u00a0hormone adrenaline<\/a>. This hormone causes the breakdown of glycogen (the\u00a0carbohydrate\u00a0used for\u00a0energy\u00a0storage in animals) to glucose<\/a>, which can be used as an energy source. This catabolic chemical process is exothermic<\/a>, or heat producing.<\/li>\n<\/ul>\n
Blood Glucose<\/h2>\n
In controlling\u00a0the blood glucose level, certain endocrine\u00a0cells\u00a0in the\u00a0pancreas\u00a0(called alpha and beta cells) detect the level of glucose in the blood. They then respond appropriately to keep the level of blood glucose within the normal range.<\/p>\n
- \n
- If the blood glucose level rises above the normal range, pancreatic beta cells release the\u00a0hormone\u00a0insulin into the bloodstream. Insulin signals cells to take up the excess glucose from the blood until the level of blood glucose decreases to the normal range.<\/li>\n
- If the blood glucose level falls below the normal range, pancreatic alpha cells release the hormone\u00a0glucagon<\/strong>\u00a0into the bloodstream. Glucagon signals cells to break down stored glycogen to glucose and release the glucose into the blood until the level of blood glucose increases to the normal range.<\/li>\n<\/ul>\n\n
<\/p>\n
Figure 7.8.4 Your liver plays an important role in balancing blood sugar levels. Glycogen in your liver can either collect glucose out of your blood stream to lower blood sugar, or release glucose into the bloodstream to increase blood sugar.\u00a0 This happens through a negative feedback loop.<\/em><\/figcaption><\/figure>\n <\/p>\n
https:\/\/www.youtube.com\/watch?v=Iz0Q9nTZCw4<\/p>\n
Homeostasis and Negative\/Positive Feedback, Amoeba Sisters, 2017.<\/p>\n
Positive Feedback<\/h1>\n<\/div>\n
In a\u00a0positive feedback loop<\/a><\/strong>, feedback serves to intensify a response until an end point is reached. Examples of processes controlled by positive feedback in the human body include blood clotting and childbirth.<\/p>\n
Blood Clotting<\/h2>\n
Figure 7.8.5 The diagram demonstrates positive feedback, using the example of blood clotting in the body. The damaged blood vessel wall releases chemicals that initiate the formation of a blood clot. Every time the blood clot builds up more, more chemicals are released that speed up the process. The process gets faster and faster until the blood vessel wall is completely healed and the positive feedback loop has ended. The graph represents the number of platelets aiding in the formation of the blood clot. The exponential form of the graph represents the positive feedback mechanism.<\/em><\/figcaption><\/figure>\n When a wound causes bleeding, the body responds with a positive feedback loop to clot the blood and stop blood loss. Substances released by the injured blood vessel wall begin the process of blood clotting. Platelets in the blood start to cling to the injured site and release chemicals that attract additional platelets. As the platelets continue to amass, more of the chemicals are released and more platelets are attracted to the site of the clot. The positive feedback accelerates the process of clotting until the clot is large enough to stop the bleeding.<\/p>\n
Childbirth<\/h2>\n
Figure 7.8.6 shows the positive feedback loop that controls childbirth. The process normally begins when the head of the infant pushes against the cervix. This stimulates nerve impulses, which travel from the cervix to the hypothalamus in the brain. In response, the hypothalamus sends the hormone oxytocin<\/a><\/strong>\u00a0to the\u00a0pituitary gland,\u00a0which secretes it into the bloodstream so it can be carried to the uterus. Oxytocin stimulates uterine contractions, which push the baby harder against the cervix. In response, the cervix starts to dilate in preparation for the passage of the baby. This cycle of positive feedback continues, with increasing levels of oxytocin, stronger uterine contractions, and wider dilation of the cervix until the baby is pushed through the birth canal and out of the body. At that point, the cervix is no longer stimulated to send\u00a0nerve impulses\u00a0to the brain, and the entire process stops.<\/p>\n
Figure 7.8.6 Normal childbirth is driven by a positive feedback loop.\u00a0<\/em><\/figcaption><\/figure>\n \nNormal childbirth is driven by a positive feedback loop. Positive feedback causes an increasing deviation from the normal state to a fixed end point, rather than a return to a normal set point as in homeostasis.<\/p>\n<\/div>\n
\nWhen Homeostasis Fails<\/h1>\n<\/div>\n
Homeostatic mechanisms work continuously to maintain stable conditions in the human body. Sometimes, however, the mechanisms fail. When they do,\u00a0homeostatic imbalance<\/a><\/strong>\u00a0may result, in which cells may not get everything they need or toxic wastes may accumulate in the body. If homeostasis is not restored, the imbalance may lead to disease \u2014 or even death.\u00a0Diabetes<\/a>\u00a0is an example of a disease caused by homeostatic imbalance. In the case of diabetes, blood glucose levels are no longer regulated and may be dangerously high. Medical intervention can help restore homeostasis and possibly prevent permanent damage to the organism.<\/p>\n
Normal aging may bring about a reduction in the\u00a0efficiency\u00a0of the body\u2019s control systems, which makes the body more susceptible to disease.\u00a0Older people, for example, may have a harder time regulating their body temperature. This is one reason they are more likely than younger people to develop serious heat-induced illnesses, such as heat stroke.<\/p>\n
\nFeature: My Human Body<\/h1>\n<\/div>\n
Diabetes<\/a>\u00a0is diagnosed in people who have abnormally high levels of blood glucose after fasting for at least 12 hours. A fasting level of blood glucose below 100 is normal. A level between 100 and 125 places you in the pre-diabetes category, and a level higher than 125 results in a diagnosis of diabetes.<\/p>\n
Of the two types of diabetes, type 2 diabetes<\/a> is the most common, accounting for about 90 per cent of all cases of diabetes in the United States. Type 2 diabetes<\/a> typically starts after the age of 40. However, because of the dramatic increase in recent decades in obesity in younger people, the age at which type 2 diabetes is diagnosed has fallen. Even children are now being diagnosed with type 2 diabetes. Today, about 3 million Canadians (8.1% of total population) are living with diabetes.<\/p>\n
You may at some point have your blood glucose level tested during a routine medical exam. If your blood glucose level indicates that you have diabetes, it may come as a shock to you because you may not have any symptoms of the disease. You are not alone, because as many as one in four diabetics do not know they have the disease. Once the diagnosis of diabetes sinks in, you may be devastated by the news. Diabetes can lead to heart attacks, strokes, blindness, kidney failure, nerve damage, and loss of toes or feet. The risk of death in adults with diabetes is 50 per cent greater than it is in adults without diabetes, and diabetes is the seventh leading cause of death of adults. In addition, controlling diabetes usually requires frequent blood glucose testing, watching what and when you eat, and taking medications or even insulin injections. All of this may seem overwhelming.<\/p>\n
The good news is that changing your lifestyle may stop the progression of type 2 diabetes or even reverse it. By adopting healthier habits, you may be able to keep your blood glucose level within the normal range without medications or insulin. Here\u2019s how:<\/p>\n
- \n
- Lose\u00a0weight.<\/strong> Any\u00a0weight\u00a0loss is beneficial. Losing as little as\u00a0seven\u00a0per cent of your\u00a0weight\u00a0may be all that is needed to stop diabetes in its tracks. It is especially important to eliminate excess weight around your waist.<\/li>\n
- Exercise\u00a0regularly.<\/strong>\u00a0You should try to\u00a0exercise\u00a0for at least 30 minutes, five days a week. This will not only lower your blood sugar and help your insulin work better, but it will also lower your\u00a0blood pressure\u00a0and improve your\u00a0heart\u00a0health. Another bonus of exercise is that it will help you lose weight by increasing your basal metabolic rate.<\/li>\n
- Adopt a healthy diet.<\/strong> Decrease your consumption of refined carbohydrates, such as sweets and sugary drinks. Increase your intake of fibre-rich foods, such as fruits, vegetables, and whole grains. About one-quarter of each meal should consist of high-protein foods, such as fish, chicken, dairy products, legumes, or nuts.<\/li>\n
- Control stress.<\/strong>\u00a0Stress can increase your blood glucose and also raise your\u00a0blood pressure\u00a0and risk of\u00a0heart\u00a0disease. When you feel stressed out, do\u00a0breathing\u00a0exercises or take a brisk walk or jog.\u00a0Try to replace stressful thoughts with more calming ones.<\/li>\n
- Establish a support system.<\/strong>\u00a0Enlist the help and support of loved ones, as well as medical professionals, such as a nutritionist and diabetes educator. Having a support system will help ensure that you are on the path to wellness, and that you can stick to your plan.<\/li>\n<\/ul>\n
\n\n\n 7.8 Summary<\/span><\/h1>\n<\/header>\n
\n- \n
- Homeostasis<\/a> is the condition in which a system (such as the human body) is maintained in a more or less steady state. It is the job of cells, tissues, organs, and organ systems throughout the body to maintain homeostasis.<\/li>\n
- For any given variable, such as body temperature, there is a particular set point<\/a> that is the physiological optimum value. The spread of values around the set point that is considered insignificant is called the normal range<\/a>.<\/li>\n
- Homeostasis is generally maintained by a negative feedback loop<\/a> that includes a stimulus<\/a>, sensor<\/a>, control centre<\/a>, and effector<\/a>. Negative feedback serves to reduce an excessive response and to keep a variable within the normal range. Negative feedback loops control body temperature and the blood glucose level.<\/li>\n
- Positive feedback loops<\/a>\u00a0are not common in biological systems. Positive feedback serves to intensify a response until an end point is reached. Positive feedback loops control blood clotting and childbirth.<\/li>\n
- Sometimes homeostatic mechanisms fail, resulting in homeostatic imbalance<\/a>. Diabetes is an example of a disease caused by homeostatic imbalance. Aging can bring about a reduction in the\u00a0efficiency\u00a0of the body\u2019s control system,\u00a0which makes\u00a0the elderly more susceptible to disease.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n
\n\n 7.8 Review Questions<\/span><\/h1>\n<\/header>\n
\n- \n
- \n\n
- For any given variable, such as body temperature, there is a particular set point<\/a> that is the physiological optimum value. The spread of values around the set point that is considered insignificant is called the normal range<\/a>.<\/li>\n
- Exercise\u00a0regularly.<\/strong>\u00a0You should try to\u00a0exercise\u00a0for at least 30 minutes, five days a week. This will not only lower your blood sugar and help your insulin work better, but it will also lower your\u00a0blood pressure\u00a0and improve your\u00a0heart\u00a0health. Another bonus of exercise is that it will help you lose weight by increasing your basal metabolic rate.<\/li>\n
- Lose\u00a0weight.<\/strong> Any\u00a0weight\u00a0loss is beneficial. Losing as little as\u00a0seven\u00a0per cent of your\u00a0weight\u00a0may be all that is needed to stop diabetes in its tracks. It is especially important to eliminate excess weight around your waist.<\/li>\n
- The\u00a0adrenal glands<\/a>\u00a0may also be stimulated to secrete the\u00a0hormone adrenaline<\/a>. This hormone causes the breakdown of glycogen (the\u00a0carbohydrate\u00a0used for\u00a0energy\u00a0storage in animals) to glucose<\/a>, which can be used as an energy source. This catabolic chemical process is exothermic<\/a>, or heat producing.<\/li>\n<\/ul>\n
- The\u00a0sensor<\/a><\/strong> monitors the values of the variable and sends data on it to the control centre.<\/li>\n
- The\u00a0stimulus<\/a><\/strong>\u00a0is provided by the variable being regulated. Generally, the stimulus indicates that the value of the variable has moved away from the set point or has left the normal range.<\/li>\n
- The organization of the body from atoms<\/a> and molecules<\/a> up through cells<\/a>, tissues, organs, and organ systems.<\/li>\n
![Hydrocephalus<\/a>\u00a0by](\"https:\/\/commons.wikimedia.org\/wiki\/File:Hydrocephalus_CDC.png\"){kind=link}