Overview of the Nervous System<\/h1>\r\n<\/div>\r\nThe\u00a0[pb_glossary id=\"2908\"]nervous system[\/pb_glossary]<\/strong>, illustrated in the sketch below, is the human organ system that coordinates all of the body\u2019s [pb_glossary id=\"3004\"]voluntary[\/pb_glossary] and [pb_glossary id=\"3005\"]involuntary[\/pb_glossary] actions, by transmitting electrical signals to and from different parts of the body. Specifically, the nervous system extracts information from the internal and external environments, using [pb_glossary id=\"3006\"]sensory receptors[\/pb_glossary]. Usually, it then\u00a0sends signals encoding this information to the [pb_glossary id=\"5915\"]brain[\/pb_glossary], which processes the information to determine an appropriate response. Finally, the brain sends signals to\u00a0muscles, [pb_glossary id=\"2803\"]organs[\/pb_glossary], or glands to bring about the response. In the example above, your\u00a0eyes\u00a0detected the boy, the information traveled to your brain, and your brain\u00a0told\u00a0your body to act so as to avoid a collision.\r\n\r\n[caption id=\"attachment_3007\" align=\"aligncenter\" width=\"766\"]![\"Nervous](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/Nervous_system_diagram.svg_-2.png\")
Figure 8.2.2 The human nervous system consists of the brain and spinal cord (central nervous system) and a network of branching nerves that travel throughout the body (peripheral nervous system). Some of the major nerves in the peripheral system are identified in this drawing.<\/em>[\/caption]\r\n\r\n\r\nSignals of the Nervous System<\/h2>\r\n<\/div>\r\nThe signals sent by the nervous system are electrical signals called\u00a0[pb_glossary id=\"5697\"]nerve impulses[\/pb_glossary]<\/strong>, and they are transmitted by special nervous system\u00a0cells called\u00a0[pb_glossary id=\"2984\"]neurons[\/pb_glossary]<\/strong> (or nerve cells), like the one in Figure 8.2.3. Long projections (called axons) from neurons carry nerve impulses directly to specific target cells. A cell that receives nerve impulses from a neuron (typically a muscle or a gland) may be excited to perform a function, inhibited from carrying out an action, or otherwise controlled. In this way, the information transmitted by the nervous system is specific to particular cells and is transmitted very rapidly. In fact, the fastest nerve impulses travel at speeds greater than 100 metres per second! Compare this to the chemical messages carried by the hormones that are secreted into the blood by endocrine glands. These hormonal messages are \u201cbroadcast\u201d to all the cells of the body, and they can travel only as quickly as the blood flows through the cardiovascular system.\r\n\r\n[caption id=\"attachment_3008\" align=\"aligncenter\" width=\"859\"]![\"Neuron\"](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/MultipolarNeuron-2.png\")
Figure 8.2.3 This model of a nerve cell shows part of its long axon which carries nerve impulses to other cells. The multiple shorter projections are called dendrites, and they receive nerve impulses from other cells.<\/em>[\/caption]\r\n\r\n\r\n\r\nThis simple model of a nerve cell shows part of its long axon which carries nerve impulses to other cells. The multiple shorter projections are called dendrites, and they receive nerve impulses from other cells.\r\n\r\n<\/div>\r\nOrganization of the Nervous System<\/h2>\r\nAs you might predict, the human [pb_glossary id=\"2908\"]nervous system[\/pb_glossary] is very complex. It has multiple divisions, beginning with its two main parts, the [pb_glossary id=\"5933\"]central nervous system[\/pb_glossary] (CNS) and the [pb_glossary id=\"3009\"]peripheral nervous system[\/pb_glossary] (PNS), as shown in the diagram below (Figure 8.2.4). The CNS includes the [pb_glossary id=\"5915\"]brain[\/pb_glossary] and [pb_glossary id=\"3010\"]spinal cord[\/pb_glossary], and the PNS consists mainly of [pb_glossary id=\"3011\"]nerves[\/pb_glossary]<\/strong>, which are bundles of [pb_glossary id=\"5901\"]axons[\/pb_glossary] from neurons. The nerves of the PNS connect the CNS to the rest of the body.\r\n\r\n[caption id=\"attachment_3013\" align=\"aligncenter\" width=\"648\"]![\"Central](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/Overview_of_Nervous_System-2.jpg\")
Figure 8.2.4 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.[\/caption]\r\n\r\n\r\n\r\nThe PNS can be further subdivided into two divisions, known as the [pb_glossary id=\"2935\"]autonomic [\/pb_glossary]and [pb_glossary id=\"3014\"]somatic nervous system[\/pb_glossary]s (Figure 8.2.5<\/span>).\u00a0These divisions control different types of functions,\u00a0and they often interact with the CNS to carry out these functions. The somatic nervous system controls activities that are under [pb_glossary id=\"3004\"]voluntary[\/pb_glossary] control, such as turning a steering wheel. The autonomic nervous system controls activities that are [pb_glossary id=\"3005\"]not under voluntary control[\/pb_glossary], such as digesting a meal. The autonomic nervous system has\u00a0three\u00a0main\u00a0divisions: the [pb_glossary id=\"3015\"]sympathetic division[\/pb_glossary] (which controls the fight-or-flight response during emergencies), the [pb_glossary id=\"3016\"]parasympathetic division[\/pb_glossary] (which controls the routine \u201chousekeeping\u201d functions of the body at other times),\u00a0and the [pb_glossary id=\"5987\"]enteric division[\/pb_glossary] (which provides local control of the digestive system).\u00a0<\/span>\r\n\r\n<\/div>\r\n\r\n[caption id=\"attachment_3018\" align=\"aligncenter\" width=\"500\"]![\"Divisions](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/Divisions-of-the-Nervous-System-2.png\")
Figure 8.2.5 Divisions of the Nervous System. <\/em>[\/caption]\r\n\r\n \r\n\r\n\r\n8.2 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- The [pb_glossary id=\"2908\"]nervous system[\/pb_glossary] is the human organ system that coordinates all of the body\u2019s [pb_glossary id=\"3004\"]voluntary[\/pb_glossary] and [pb_glossary id=\"3005\"]involuntary[\/pb_glossary] actions, by transmitting signals to and from different parts of the body.<\/li>\r\n \t
- The nervous system has two major divisions, called the\u00a0[pb_glossary id=\"5933\"]central nervous system[\/pb_glossary]\u00a0(CNS) and the\u00a0[pb_glossary id=\"3009\"]peripheral nervous system[\/pb_glossary]\u00a0(PNS). The CNS\u00a0includes\u00a0the [pb_glossary id=\"5915\"]brain[\/pb_glossary] and [pb_glossary id=\"3010\"]spinal cord[\/pb_glossary], and the PNS consists mainly of [pb_glossary id=\"3011\"]nerves[\/pb_glossary]\u00a0that connect the CNS with the rest of the body.<\/li>\r\n \t
- The PNS\u00a0can be subdivided into\u00a0two major divisions: the [pb_glossary id=\"3014\"]somatic nervous system[\/pb_glossary] and the [pb_glossary id=\"5899\"]autonomic nervous system[\/pb_glossary].The somatic system controls activities that are under voluntary control. The autonomic system controls activities that are not under voluntary control. The autonomic nervous system is further divided into the [pb_glossary id=\"3015\"]sympathetic division[\/pb_glossary] (which controls the fight-or-flight response), the [pb_glossary id=\"3016\"]parasympathetic division[\/pb_glossary] (which controls most routine involuntary responses),\u00a0and the [pb_glossary id=\"5987\"]enteric division[\/pb_glossary] (which provides local control of the digestive system).<\/li>\r\n \t
- Electrical signals sent by the nervous system are called\u00a0[pb_glossary id=\"5697\"]nerve impulses[\/pb_glossary]. They are transmitted by special\u00a0cells\u00a0called [pb_glossary id=\"2984\"]neurons[\/pb_glossary]. Nerve impulses can travel to specific target cells very rapidly.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n8.2 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- List the general steps through which the nervous system generates\u00a0an appropriate response to information from the internal and external environments.<\/li>\r\n \t
- What are neurons?<\/li>\r\n \t
- Compare and contrast the central and peripheral nervous systems.<\/li>\r\n \t
- [h5p id=\"553\"]<\/li>\r\n \t
- Which major division of the peripheral nervous system allows you to\u00a0walk to class? Which major division of the peripheral nervous system\u00a0controls your\u00a0heart\u00a0rate?<\/li>\r\n \t
- Identify the functions of the three\u00a0main\u00a0divisions of the autonomic nervous system.<\/li>\r\n \t
- [h5p id=\"554\"]<\/li>\r\n \t
- What is an axon, and what is its function?<\/li>\r\n \t
- Define nerve impulses.<\/li>\r\n \t
- Explain generally how the brain and spinal cord can interact with and control the rest of the body.<\/li>\r\n \t
- How are nerves and neurons related?<\/li>\r\n \t
- What type of information from the outside environment do you think is detected by sensory receptors in your ears?<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
\r\n8.2 Explore More<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=qPix_X-9t7E\r\nThe Nervous System, Part 1: Crash Course A&P #8, CrashCourse, 2015.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=Nsxw5_Iz7mY&feature=emb_logo\r\n
Engineering the Human Nervous System: Megan Moynahan at TEDxBrussels,\r\nTEDx Talks, 2013.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n \r\n\r\n<\/div>\r\n
Attributions<\/h2>\r\nFigure 8.2.1<\/strong>\r\n\r\nSkateboard_1613<\/a> by Autoria propia on Wikimedia Commons is released into the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain) (Derivative work of this file:\u00a0\u00a0SkateboardinDog.jpg)<\/a>\r\n\r\nFigure 8.2.2<\/strong>\r\n\r\nNervous_system_diagram.svg<\/a>\u00a0by\u00a0<\/span>The Emirr<\/a> on Wikimedia Commons is used under a\u00a0CC BY 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0\/deed.en) license.\r\n\r\nFigure 8.2.3<\/strong>\r\n\r\nMultipolarNeuron<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0\/deed.en) license.\r\n\r\nFigure 8.2.4<\/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 8.2.5<\/strong>\r\n\r\nDivisions of the Nervous System<\/a>\u00a0by CK-12 Foundation<\/a> is used under the CC BY-NC 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-nc\/3.0\/) license.\r\n![\"\"](\"https:\/\/www.ck12info.org\/wp-content\/uploads\/2016\/05\/logo_ck12.png\")
\u00a9<\/span>CK-12 Foundation<\/a> Licensed under\u00a0<\/span>![\"CK-12](\"https:\/\/www.ck12info.org\/wp-content\/uploads\/2016\/05\/icon_licence.png\" "\\"CK-12")
<\/a>\u00a0\u2022\u00a0<\/span>Terms of Use<\/a>\u00a0\u2022\u00a0<\/span>Attribution<\/a><\/div>\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, April 25). Figure\u00a0<\/span>12.2<\/span>\u00a0<\/span>Central and peripheral nervous system <\/span>[digital image].\u00a0 In Anatomy and Physiology<\/em> (Section 12.1). OpenStax. https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/12-1-basic-structure-and-function-of-the-nervous-system<\/p>\r\nBrainard, J\/ CK-12 Foundation. (2016). Figure 5\u00a0 [digital image]. In CK-12 College Human Biology<\/em> (Section 10.2) [online Flexbook]. CK12.org. https:\/\/www.ck12.org\/book\/ck-12-college-human-biology\/section\/10.2\/<\/p>\r\nCrashCourse. (2015, February 23). The nervous system, Part 1: Crash Course A&P #8. YouTube. https:\/\/www.youtube.com\/watch?v=qPix_X-9t7E&feature=youtu.be<\/p>\r\n
TEDx Talks. (2013, November 3). Engineering the human nervous system: Megan Moynahan at TEDxBrussels. YouTube. https:\/\/www.youtube.com\/watch?v=Nsxw5_Iz7mY&feature=youtu.be<\/p>","rendered":"
<\/p>\n![\"\"](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2019\/06\/Skateboard_1613-2.jpg\")
Figure 8.2.1 What would you do if this skateboarder suddenly appeared in front of your moving car?\u00a0<\/em><\/figcaption><\/figure>\nIn the Blink of an Eye<\/h1>\n
As you drive into a parking lot, a boy on a skateboard suddenly flies in front of your car across your field of\u00a0vision. You see the boy in the nick of time and react immediately. You slam on the brakes and steer sharply to the right \u2014 all in the blink of an eye. You avoid a collision, but just barely. You\u2019re shaken up, but thankful that no one was hurt. How did you respond so quickly? Rapid responses like this are controlled by your nervous system.<\/p>\n
\nOverview of the Nervous System<\/h1>\n<\/div>\n
The\u00a0nervous system<\/a><\/strong>, illustrated in the sketch below, is the human organ system that coordinates all of the body\u2019s voluntary<\/a> and involuntary<\/a> actions, by transmitting electrical signals to and from different parts of the body. Specifically, the nervous system extracts information from the internal and external environments, using sensory receptors<\/a>. Usually, it then\u00a0sends signals encoding this information to the brain<\/a>, which processes the information to determine an appropriate response. Finally, the brain sends signals to\u00a0muscles, organs<\/a>, or glands to bring about the response. In the example above, your\u00a0eyes\u00a0detected the boy, the information traveled to your brain, and your brain\u00a0told\u00a0your body to act so as to avoid a collision.<\/p>\nFigure 8.2.2 The human nervous system consists of the brain and spinal cord (central nervous system) and a network of branching nerves that travel throughout the body (peripheral nervous system). Some of the major nerves in the peripheral system are identified in this drawing.<\/em><\/figcaption><\/figure>\n\nSignals of the Nervous System<\/h2>\n<\/div>\n
The signals sent by the nervous system are electrical signals called\u00a0nerve impulses<\/a><\/strong>, and they are transmitted by special nervous system\u00a0cells called\u00a0neurons<\/a><\/strong> (or nerve cells), like the one in Figure 8.2.3. Long projections (called axons) from neurons carry nerve impulses directly to specific target cells. A cell that receives nerve impulses from a neuron (typically a muscle or a gland) may be excited to perform a function, inhibited from carrying out an action, or otherwise controlled. In this way, the information transmitted by the nervous system is specific to particular cells and is transmitted very rapidly. In fact, the fastest nerve impulses travel at speeds greater than 100 metres per second! Compare this to the chemical messages carried by the hormones that are secreted into the blood by endocrine glands. These hormonal messages are \u201cbroadcast\u201d to all the cells of the body, and they can travel only as quickly as the blood flows through the cardiovascular system.<\/p>\nFigure 8.2.3 This model of a nerve cell shows part of its long axon which carries nerve impulses to other cells. The multiple shorter projections are called dendrites, and they receive nerve impulses from other cells.<\/em><\/figcaption><\/figure>\n\nThis simple model of a nerve cell shows part of its long axon which carries nerve impulses to other cells. The multiple shorter projections are called dendrites, and they receive nerve impulses from other cells.<\/p>\n<\/div>\n
Organization of the Nervous System<\/h2>\n
As you might predict, the human nervous system<\/a> is very complex. It has multiple divisions, beginning with its two main parts, the central nervous system<\/a> (CNS) and the peripheral nervous system<\/a> (PNS), as shown in the diagram below (Figure 8.2.4). The CNS includes the brain<\/a> and spinal cord<\/a>, and the PNS consists mainly of nerves<\/a><\/strong>, which are bundles of axons<\/a> from neurons. The nerves of the PNS connect the CNS to the rest of the body.<\/p>\nFigure 8.2.4 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.<\/figcaption><\/figure>\n\nThe PNS can be further subdivided into two divisions, known as the autonomic <\/a>and somatic nervous system<\/a>s (Figure 8.2.5<\/span>).\u00a0These divisions control different types of functions,\u00a0and they often interact with the CNS to carry out these functions. The somatic nervous system controls activities that are under voluntary<\/a> control, such as turning a steering wheel. The autonomic nervous system controls activities that are not under voluntary control<\/a>, such as digesting a meal. The autonomic nervous system has\u00a0three\u00a0main\u00a0divisions: the sympathetic division<\/a> (which controls the fight-or-flight response during emergencies), the parasympathetic division<\/a> (which controls the routine \u201chousekeeping\u201d functions of the body at other times),\u00a0and the enteric division<\/a> (which provides local control of the digestive system).\u00a0<\/span><\/p>\n<\/div>\nFigure 8.2.5 Divisions of the Nervous System. <\/em><\/figcaption><\/figure>\n <\/p>\n
\n\n\n8.2 Summary<\/span><\/h1>\n<\/header>\n\n\n- The nervous system<\/a> is the human organ system that coordinates all of the body\u2019s voluntary<\/a> and involuntary<\/a> actions, by transmitting signals to and from different parts of the body.<\/li>\n
- The nervous system has two major divisions, called the\u00a0central nervous system<\/a>\u00a0(CNS) and the\u00a0peripheral nervous system<\/a>\u00a0(PNS). The CNS\u00a0includes\u00a0the brain<\/a> and spinal cord<\/a>, and the PNS consists mainly of nerves<\/a>\u00a0that connect the CNS with the rest of the body.<\/li>\n
- The PNS\u00a0can be subdivided into\u00a0two major divisions: the somatic nervous system<\/a> and the autonomic nervous system<\/a>.The somatic system controls activities that are under voluntary control. The autonomic system controls activities that are not under voluntary control. The autonomic nervous system is further divided into the sympathetic division<\/a> (which controls the fight-or-flight response), the parasympathetic division<\/a> (which controls most routine involuntary responses),\u00a0and the enteric division<\/a> (which provides local control of the digestive system).<\/li>\n
- Electrical signals sent by the nervous system are called\u00a0nerve impulses<\/a>. They are transmitted by special\u00a0cells\u00a0called neurons<\/a>. Nerve impulses can travel to specific target cells very rapidly.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n
\n8.2 Review Questions<\/span><\/h1>\n<\/header>\n\n\n- List the general steps through which the nervous system generates\u00a0an appropriate response to information from the internal and external environments.<\/li>\n
- What are neurons?<\/li>\n
- Compare and contrast the central and peripheral nervous systems.<\/li>\n
- \n\n
Signals of the Nervous System<\/h2>\r\n<\/div>\r\nThe signals sent by the nervous system are electrical signals called\u00a0[pb_glossary id=\"5697\"]nerve impulses[\/pb_glossary]<\/strong>, and they are transmitted by special nervous system\u00a0cells called\u00a0[pb_glossary id=\"2984\"]neurons[\/pb_glossary]<\/strong> (or nerve cells), like the one in Figure 8.2.3. Long projections (called axons) from neurons carry nerve impulses directly to specific target cells. A cell that receives nerve impulses from a neuron (typically a muscle or a gland) may be excited to perform a function, inhibited from carrying out an action, or otherwise controlled. In this way, the information transmitted by the nervous system is specific to particular cells and is transmitted very rapidly. In fact, the fastest nerve impulses travel at speeds greater than 100 metres per second! Compare this to the chemical messages carried by the hormones that are secreted into the blood by endocrine glands. These hormonal messages are \u201cbroadcast\u201d to all the cells of the body, and they can travel only as quickly as the blood flows through the cardiovascular system.\r\n\r\n[caption id=\"attachment_3008\" align=\"aligncenter\" width=\"859\"] Figure 8.2.3 This model of a nerve cell shows part of its long axon which carries nerve impulses to other cells. The multiple shorter projections are called dendrites, and they receive nerve impulses from other cells.<\/em>[\/caption]\r\n\r\n\r\n\r\nThis simple model of a nerve cell shows part of its long axon which carries nerve impulses to other cells. The multiple shorter projections are called dendrites, and they receive nerve impulses from other cells.\r\n\r\n<\/div>\r\nOrganization of the Nervous System<\/h2>\r\nAs you might predict, the human [pb_glossary id=\"2908\"]nervous system[\/pb_glossary] is very complex. It has multiple divisions, beginning with its two main parts, the [pb_glossary id=\"5933\"]central nervous system[\/pb_glossary] (CNS) and the [pb_glossary id=\"3009\"]peripheral nervous system[\/pb_glossary] (PNS), as shown in the diagram below (Figure 8.2.4). The CNS includes the [pb_glossary id=\"5915\"]brain[\/pb_glossary] and [pb_glossary id=\"3010\"]spinal cord[\/pb_glossary], and the PNS consists mainly of [pb_glossary id=\"3011\"]nerves[\/pb_glossary]<\/strong>, which are bundles of [pb_glossary id=\"5901\"]axons[\/pb_glossary] from neurons. The nerves of the PNS connect the CNS to the rest of the body.\r\n\r\n[caption id=\"attachment_3013\" align=\"aligncenter\" width=\"648\"] Figure 8.2.4 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.[\/caption]\r\n\r\n\r\n\r\nThe PNS can be further subdivided into two divisions, known as the [pb_glossary id=\"2935\"]autonomic [\/pb_glossary]and [pb_glossary id=\"3014\"]somatic nervous system[\/pb_glossary]s (Figure 8.2.5<\/span>).\u00a0These divisions control different types of functions,\u00a0and they often interact with the CNS to carry out these functions. The somatic nervous system controls activities that are under [pb_glossary id=\"3004\"]voluntary[\/pb_glossary] control, such as turning a steering wheel. The autonomic nervous system controls activities that are [pb_glossary id=\"3005\"]not under voluntary control[\/pb_glossary], such as digesting a meal. The autonomic nervous system has\u00a0three\u00a0main\u00a0divisions: the [pb_glossary id=\"3015\"]sympathetic division[\/pb_glossary] (which controls the fight-or-flight response during emergencies), the [pb_glossary id=\"3016\"]parasympathetic division[\/pb_glossary] (which controls the routine \u201chousekeeping\u201d functions of the body at other times),\u00a0and the [pb_glossary id=\"5987\"]enteric division[\/pb_glossary] (which provides local control of the digestive system).\u00a0<\/span>\r\n\r\n<\/div>\r\n\r\n[caption id=\"attachment_3018\" align=\"aligncenter\" width=\"500\"] Figure 8.2.5 Divisions of the Nervous System. <\/em>[\/caption]\r\n\r\n \r\n\r\n\r\n8.2 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- The [pb_glossary id=\"2908\"]nervous system[\/pb_glossary] is the human organ system that coordinates all of the body\u2019s [pb_glossary id=\"3004\"]voluntary[\/pb_glossary] and [pb_glossary id=\"3005\"]involuntary[\/pb_glossary] actions, by transmitting signals to and from different parts of the body.<\/li>\r\n \t
- The nervous system has two major divisions, called the\u00a0[pb_glossary id=\"5933\"]central nervous system[\/pb_glossary]\u00a0(CNS) and the\u00a0[pb_glossary id=\"3009\"]peripheral nervous system[\/pb_glossary]\u00a0(PNS). The CNS\u00a0includes\u00a0the [pb_glossary id=\"5915\"]brain[\/pb_glossary] and [pb_glossary id=\"3010\"]spinal cord[\/pb_glossary], and the PNS consists mainly of [pb_glossary id=\"3011\"]nerves[\/pb_glossary]\u00a0that connect the CNS with the rest of the body.<\/li>\r\n \t
- The PNS\u00a0can be subdivided into\u00a0two major divisions: the [pb_glossary id=\"3014\"]somatic nervous system[\/pb_glossary] and the [pb_glossary id=\"5899\"]autonomic nervous system[\/pb_glossary].The somatic system controls activities that are under voluntary control. The autonomic system controls activities that are not under voluntary control. The autonomic nervous system is further divided into the [pb_glossary id=\"3015\"]sympathetic division[\/pb_glossary] (which controls the fight-or-flight response), the [pb_glossary id=\"3016\"]parasympathetic division[\/pb_glossary] (which controls most routine involuntary responses),\u00a0and the [pb_glossary id=\"5987\"]enteric division[\/pb_glossary] (which provides local control of the digestive system).<\/li>\r\n \t
- Electrical signals sent by the nervous system are called\u00a0[pb_glossary id=\"5697\"]nerve impulses[\/pb_glossary]. They are transmitted by special\u00a0cells\u00a0called [pb_glossary id=\"2984\"]neurons[\/pb_glossary]. Nerve impulses can travel to specific target cells very rapidly.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n8.2 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- List the general steps through which the nervous system generates\u00a0an appropriate response to information from the internal and external environments.<\/li>\r\n \t
- What are neurons?<\/li>\r\n \t
- Compare and contrast the central and peripheral nervous systems.<\/li>\r\n \t
- [h5p id=\"553\"]<\/li>\r\n \t
- Which major division of the peripheral nervous system allows you to\u00a0walk to class? Which major division of the peripheral nervous system\u00a0controls your\u00a0heart\u00a0rate?<\/li>\r\n \t
- Identify the functions of the three\u00a0main\u00a0divisions of the autonomic nervous system.<\/li>\r\n \t
- [h5p id=\"554\"]<\/li>\r\n \t
- What is an axon, and what is its function?<\/li>\r\n \t
- Define nerve impulses.<\/li>\r\n \t
- Explain generally how the brain and spinal cord can interact with and control the rest of the body.<\/li>\r\n \t
- How are nerves and neurons related?<\/li>\r\n \t
- What type of information from the outside environment do you think is detected by sensory receptors in your ears?<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
\r\n8.2 Explore More<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=qPix_X-9t7E\r\nThe Nervous System, Part 1: Crash Course A&P #8, CrashCourse, 2015.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=Nsxw5_Iz7mY&feature=emb_logo\r\n
Engineering the Human Nervous System: Megan Moynahan at TEDxBrussels,\r\nTEDx Talks, 2013.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n \r\n\r\n<\/div>\r\n
Attributions<\/h2>\r\nFigure 8.2.1<\/strong>\r\n\r\nSkateboard_1613<\/a> by Autoria propia on Wikimedia Commons is released into the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain) (Derivative work of this file:\u00a0\u00a0SkateboardinDog.jpg)<\/a>\r\n\r\nFigure 8.2.2<\/strong>\r\n\r\nNervous_system_diagram.svg<\/a>\u00a0by\u00a0<\/span>The Emirr<\/a> on Wikimedia Commons is used under a\u00a0CC BY 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0\/deed.en) license.\r\n\r\nFigure 8.2.3<\/strong>\r\n\r\nMultipolarNeuron<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0\/deed.en) license.\r\n\r\nFigure 8.2.4<\/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 8.2.5<\/strong>\r\n\r\nDivisions of the Nervous System<\/a>\u00a0by CK-12 Foundation<\/a> is used under the CC BY-NC 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-nc\/3.0\/) license.\r\n \u00a9<\/span>CK-12 Foundation<\/a> Licensed under\u00a0<\/span><\/a>\u00a0\u2022\u00a0<\/span>Terms of Use<\/a>\u00a0\u2022\u00a0<\/span>Attribution<\/a><\/div>\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, April 25). Figure\u00a0<\/span>12.2<\/span>\u00a0<\/span>Central and peripheral nervous system <\/span>[digital image].\u00a0 In Anatomy and Physiology<\/em> (Section 12.1). OpenStax. https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/12-1-basic-structure-and-function-of-the-nervous-system<\/p>\r\nBrainard, J\/ CK-12 Foundation. (2016). Figure 5\u00a0 [digital image]. In CK-12 College Human Biology<\/em> (Section 10.2) [online Flexbook]. CK12.org. https:\/\/www.ck12.org\/book\/ck-12-college-human-biology\/section\/10.2\/<\/p>\r\nCrashCourse. (2015, February 23). The nervous system, Part 1: Crash Course A&P #8. YouTube. https:\/\/www.youtube.com\/watch?v=qPix_X-9t7E&feature=youtu.be<\/p>\r\n
TEDx Talks. (2013, November 3). Engineering the human nervous system: Megan Moynahan at TEDxBrussels. YouTube. https:\/\/www.youtube.com\/watch?v=Nsxw5_Iz7mY&feature=youtu.be<\/p>","rendered":"
<\/p>\nFigure 8.2.1 What would you do if this skateboarder suddenly appeared in front of your moving car?\u00a0<\/em><\/figcaption><\/figure>\nIn the Blink of an Eye<\/h1>\n
As you drive into a parking lot, a boy on a skateboard suddenly flies in front of your car across your field of\u00a0vision. You see the boy in the nick of time and react immediately. You slam on the brakes and steer sharply to the right \u2014 all in the blink of an eye. You avoid a collision, but just barely. You\u2019re shaken up, but thankful that no one was hurt. How did you respond so quickly? Rapid responses like this are controlled by your nervous system.<\/p>\n
\nOverview of the Nervous System<\/h1>\n<\/div>\n
The\u00a0nervous system<\/a><\/strong>, illustrated in the sketch below, is the human organ system that coordinates all of the body\u2019s voluntary<\/a> and involuntary<\/a> actions, by transmitting electrical signals to and from different parts of the body. Specifically, the nervous system extracts information from the internal and external environments, using sensory receptors<\/a>. Usually, it then\u00a0sends signals encoding this information to the brain<\/a>, which processes the information to determine an appropriate response. Finally, the brain sends signals to\u00a0muscles, organs<\/a>, or glands to bring about the response. In the example above, your\u00a0eyes\u00a0detected the boy, the information traveled to your brain, and your brain\u00a0told\u00a0your body to act so as to avoid a collision.<\/p>\nFigure 8.2.2 The human nervous system consists of the brain and spinal cord (central nervous system) and a network of branching nerves that travel throughout the body (peripheral nervous system). Some of the major nerves in the peripheral system are identified in this drawing.<\/em><\/figcaption><\/figure>\n\nSignals of the Nervous System<\/h2>\n<\/div>\n
The signals sent by the nervous system are electrical signals called\u00a0nerve impulses<\/a><\/strong>, and they are transmitted by special nervous system\u00a0cells called\u00a0neurons<\/a><\/strong> (or nerve cells), like the one in Figure 8.2.3. Long projections (called axons) from neurons carry nerve impulses directly to specific target cells. A cell that receives nerve impulses from a neuron (typically a muscle or a gland) may be excited to perform a function, inhibited from carrying out an action, or otherwise controlled. In this way, the information transmitted by the nervous system is specific to particular cells and is transmitted very rapidly. In fact, the fastest nerve impulses travel at speeds greater than 100 metres per second! Compare this to the chemical messages carried by the hormones that are secreted into the blood by endocrine glands. These hormonal messages are \u201cbroadcast\u201d to all the cells of the body, and they can travel only as quickly as the blood flows through the cardiovascular system.<\/p>\nFigure 8.2.3 This model of a nerve cell shows part of its long axon which carries nerve impulses to other cells. The multiple shorter projections are called dendrites, and they receive nerve impulses from other cells.<\/em><\/figcaption><\/figure>\n\nThis simple model of a nerve cell shows part of its long axon which carries nerve impulses to other cells. The multiple shorter projections are called dendrites, and they receive nerve impulses from other cells.<\/p>\n<\/div>\n
Organization of the Nervous System<\/h2>\n
As you might predict, the human nervous system<\/a> is very complex. It has multiple divisions, beginning with its two main parts, the central nervous system<\/a> (CNS) and the peripheral nervous system<\/a> (PNS), as shown in the diagram below (Figure 8.2.4). The CNS includes the brain<\/a> and spinal cord<\/a>, and the PNS consists mainly of nerves<\/a><\/strong>, which are bundles of axons<\/a> from neurons. The nerves of the PNS connect the CNS to the rest of the body.<\/p>\nFigure 8.2.4 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.<\/figcaption><\/figure>\n\nThe PNS can be further subdivided into two divisions, known as the autonomic <\/a>and somatic nervous system<\/a>s (Figure 8.2.5<\/span>).\u00a0These divisions control different types of functions,\u00a0and they often interact with the CNS to carry out these functions. The somatic nervous system controls activities that are under voluntary<\/a> control, such as turning a steering wheel. The autonomic nervous system controls activities that are not under voluntary control<\/a>, such as digesting a meal. The autonomic nervous system has\u00a0three\u00a0main\u00a0divisions: the sympathetic division<\/a> (which controls the fight-or-flight response during emergencies), the parasympathetic division<\/a> (which controls the routine \u201chousekeeping\u201d functions of the body at other times),\u00a0and the enteric division<\/a> (which provides local control of the digestive system).\u00a0<\/span><\/p>\n<\/div>\nFigure 8.2.5 Divisions of the Nervous System. <\/em><\/figcaption><\/figure>\n <\/p>\n
\n\n\n8.2 Summary<\/span><\/h1>\n<\/header>\n\n\n- The nervous system<\/a> is the human organ system that coordinates all of the body\u2019s voluntary<\/a> and involuntary<\/a> actions, by transmitting signals to and from different parts of the body.<\/li>\n
- The nervous system has two major divisions, called the\u00a0central nervous system<\/a>\u00a0(CNS) and the\u00a0peripheral nervous system<\/a>\u00a0(PNS). The CNS\u00a0includes\u00a0the brain<\/a> and spinal cord<\/a>, and the PNS consists mainly of nerves<\/a>\u00a0that connect the CNS with the rest of the body.<\/li>\n
- The PNS\u00a0can be subdivided into\u00a0two major divisions: the somatic nervous system<\/a> and the autonomic nervous system<\/a>.The somatic system controls activities that are under voluntary control. The autonomic system controls activities that are not under voluntary control. The autonomic nervous system is further divided into the sympathetic division<\/a> (which controls the fight-or-flight response), the parasympathetic division<\/a> (which controls most routine involuntary responses),\u00a0and the enteric division<\/a> (which provides local control of the digestive system).<\/li>\n
- Electrical signals sent by the nervous system are called\u00a0nerve impulses<\/a>. They are transmitted by special\u00a0cells\u00a0called neurons<\/a>. Nerve impulses can travel to specific target cells very rapidly.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n
\n8.2 Review Questions<\/span><\/h1>\n<\/header>\n\n\n- List the general steps through which the nervous system generates\u00a0an appropriate response to information from the internal and external environments.<\/li>\n
- What are neurons?<\/li>\n
- Compare and contrast the central and peripheral nervous systems.<\/li>\n
- \n\n
Organization of the Nervous System<\/h2>\r\nAs you might predict, the human [pb_glossary id=\"2908\"]nervous system[\/pb_glossary] is very complex. It has multiple divisions, beginning with its two main parts, the [pb_glossary id=\"5933\"]central nervous system[\/pb_glossary] (CNS) and the [pb_glossary id=\"3009\"]peripheral nervous system[\/pb_glossary] (PNS), as shown in the diagram below (Figure 8.2.4). The CNS includes the [pb_glossary id=\"5915\"]brain[\/pb_glossary] and [pb_glossary id=\"3010\"]spinal cord[\/pb_glossary], and the PNS consists mainly of [pb_glossary id=\"3011\"]nerves[\/pb_glossary]<\/strong>, which are bundles of [pb_glossary id=\"5901\"]axons[\/pb_glossary] from neurons. The nerves of the PNS connect the CNS to the rest of the body.\r\n\r\n[caption id=\"attachment_3013\" align=\"aligncenter\" width=\"648\"] Figure 8.2.4 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.[\/caption]\r\n\r\n\r\n\r\nThe PNS can be further subdivided into two divisions, known as the [pb_glossary id=\"2935\"]autonomic [\/pb_glossary]and [pb_glossary id=\"3014\"]somatic nervous system[\/pb_glossary]s (Figure 8.2.5<\/span>).\u00a0These divisions control different types of functions,\u00a0and they often interact with the CNS to carry out these functions. The somatic nervous system controls activities that are under [pb_glossary id=\"3004\"]voluntary[\/pb_glossary] control, such as turning a steering wheel. The autonomic nervous system controls activities that are [pb_glossary id=\"3005\"]not under voluntary control[\/pb_glossary], such as digesting a meal. The autonomic nervous system has\u00a0three\u00a0main\u00a0divisions: the [pb_glossary id=\"3015\"]sympathetic division[\/pb_glossary] (which controls the fight-or-flight response during emergencies), the [pb_glossary id=\"3016\"]parasympathetic division[\/pb_glossary] (which controls the routine \u201chousekeeping\u201d functions of the body at other times),\u00a0and the [pb_glossary id=\"5987\"]enteric division[\/pb_glossary] (which provides local control of the digestive system).\u00a0<\/span>\r\n\r\n<\/div>\r\n\r\n[caption id=\"attachment_3018\" align=\"aligncenter\" width=\"500\"] Figure 8.2.5 Divisions of the Nervous System. <\/em>[\/caption]\r\n\r\n \r\n\r\n\r\n8.2 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- The [pb_glossary id=\"2908\"]nervous system[\/pb_glossary] is the human organ system that coordinates all of the body\u2019s [pb_glossary id=\"3004\"]voluntary[\/pb_glossary] and [pb_glossary id=\"3005\"]involuntary[\/pb_glossary] actions, by transmitting signals to and from different parts of the body.<\/li>\r\n \t
- The nervous system has two major divisions, called the\u00a0[pb_glossary id=\"5933\"]central nervous system[\/pb_glossary]\u00a0(CNS) and the\u00a0[pb_glossary id=\"3009\"]peripheral nervous system[\/pb_glossary]\u00a0(PNS). The CNS\u00a0includes\u00a0the [pb_glossary id=\"5915\"]brain[\/pb_glossary] and [pb_glossary id=\"3010\"]spinal cord[\/pb_glossary], and the PNS consists mainly of [pb_glossary id=\"3011\"]nerves[\/pb_glossary]\u00a0that connect the CNS with the rest of the body.<\/li>\r\n \t
- The PNS\u00a0can be subdivided into\u00a0two major divisions: the [pb_glossary id=\"3014\"]somatic nervous system[\/pb_glossary] and the [pb_glossary id=\"5899\"]autonomic nervous system[\/pb_glossary].The somatic system controls activities that are under voluntary control. The autonomic system controls activities that are not under voluntary control. The autonomic nervous system is further divided into the [pb_glossary id=\"3015\"]sympathetic division[\/pb_glossary] (which controls the fight-or-flight response), the [pb_glossary id=\"3016\"]parasympathetic division[\/pb_glossary] (which controls most routine involuntary responses),\u00a0and the [pb_glossary id=\"5987\"]enteric division[\/pb_glossary] (which provides local control of the digestive system).<\/li>\r\n \t
- Electrical signals sent by the nervous system are called\u00a0[pb_glossary id=\"5697\"]nerve impulses[\/pb_glossary]. They are transmitted by special\u00a0cells\u00a0called [pb_glossary id=\"2984\"]neurons[\/pb_glossary]. Nerve impulses can travel to specific target cells very rapidly.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n8.2 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- List the general steps through which the nervous system generates\u00a0an appropriate response to information from the internal and external environments.<\/li>\r\n \t
- What are neurons?<\/li>\r\n \t
- Compare and contrast the central and peripheral nervous systems.<\/li>\r\n \t
- [h5p id=\"553\"]<\/li>\r\n \t
- Which major division of the peripheral nervous system allows you to\u00a0walk to class? Which major division of the peripheral nervous system\u00a0controls your\u00a0heart\u00a0rate?<\/li>\r\n \t
- Identify the functions of the three\u00a0main\u00a0divisions of the autonomic nervous system.<\/li>\r\n \t
- [h5p id=\"554\"]<\/li>\r\n \t
- What is an axon, and what is its function?<\/li>\r\n \t
- Define nerve impulses.<\/li>\r\n \t
- Explain generally how the brain and spinal cord can interact with and control the rest of the body.<\/li>\r\n \t
- How are nerves and neurons related?<\/li>\r\n \t
- What type of information from the outside environment do you think is detected by sensory receptors in your ears?<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
\r\n8.2 Explore More<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=qPix_X-9t7E\r\nThe Nervous System, Part 1: Crash Course A&P #8, CrashCourse, 2015.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=Nsxw5_Iz7mY&feature=emb_logo\r\n
Engineering the Human Nervous System: Megan Moynahan at TEDxBrussels,\r\nTEDx Talks, 2013.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n \r\n\r\n<\/div>\r\n
Attributions<\/h2>\r\nFigure 8.2.1<\/strong>\r\n\r\nSkateboard_1613<\/a> by Autoria propia on Wikimedia Commons is released into the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain) (Derivative work of this file:\u00a0\u00a0SkateboardinDog.jpg)<\/a>\r\n\r\nFigure 8.2.2<\/strong>\r\n\r\nNervous_system_diagram.svg<\/a>\u00a0by\u00a0<\/span>The Emirr<\/a> on Wikimedia Commons is used under a\u00a0CC BY 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0\/deed.en) license.\r\n\r\nFigure 8.2.3<\/strong>\r\n\r\nMultipolarNeuron<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0\/deed.en) license.\r\n\r\nFigure 8.2.4<\/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 8.2.5<\/strong>\r\n\r\nDivisions of the Nervous System<\/a>\u00a0by CK-12 Foundation<\/a> is used under the CC BY-NC 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-nc\/3.0\/) license.\r\n \u00a9<\/span>CK-12 Foundation<\/a> Licensed under\u00a0<\/span><\/a>\u00a0\u2022\u00a0<\/span>Terms of Use<\/a>\u00a0\u2022\u00a0<\/span>Attribution<\/a><\/div>\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, April 25). Figure\u00a0<\/span>12.2<\/span>\u00a0<\/span>Central and peripheral nervous system <\/span>[digital image].\u00a0 In Anatomy and Physiology<\/em> (Section 12.1). OpenStax. https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/12-1-basic-structure-and-function-of-the-nervous-system<\/p>\r\nBrainard, J\/ CK-12 Foundation. (2016). Figure 5\u00a0 [digital image]. In CK-12 College Human Biology<\/em> (Section 10.2) [online Flexbook]. CK12.org. https:\/\/www.ck12.org\/book\/ck-12-college-human-biology\/section\/10.2\/<\/p>\r\nCrashCourse. (2015, February 23). The nervous system, Part 1: Crash Course A&P #8. YouTube. https:\/\/www.youtube.com\/watch?v=qPix_X-9t7E&feature=youtu.be<\/p>\r\n
TEDx Talks. (2013, November 3). Engineering the human nervous system: Megan Moynahan at TEDxBrussels. YouTube. https:\/\/www.youtube.com\/watch?v=Nsxw5_Iz7mY&feature=youtu.be<\/p>","rendered":"
<\/p>\nFigure 8.2.1 What would you do if this skateboarder suddenly appeared in front of your moving car?\u00a0<\/em><\/figcaption><\/figure>\nIn the Blink of an Eye<\/h1>\n
As you drive into a parking lot, a boy on a skateboard suddenly flies in front of your car across your field of\u00a0vision. You see the boy in the nick of time and react immediately. You slam on the brakes and steer sharply to the right \u2014 all in the blink of an eye. You avoid a collision, but just barely. You\u2019re shaken up, but thankful that no one was hurt. How did you respond so quickly? Rapid responses like this are controlled by your nervous system.<\/p>\n
\nOverview of the Nervous System<\/h1>\n<\/div>\n
The\u00a0nervous system<\/a><\/strong>, illustrated in the sketch below, is the human organ system that coordinates all of the body\u2019s voluntary<\/a> and involuntary<\/a> actions, by transmitting electrical signals to and from different parts of the body. Specifically, the nervous system extracts information from the internal and external environments, using sensory receptors<\/a>. Usually, it then\u00a0sends signals encoding this information to the brain<\/a>, which processes the information to determine an appropriate response. Finally, the brain sends signals to\u00a0muscles, organs<\/a>, or glands to bring about the response. In the example above, your\u00a0eyes\u00a0detected the boy, the information traveled to your brain, and your brain\u00a0told\u00a0your body to act so as to avoid a collision.<\/p>\nFigure 8.2.2 The human nervous system consists of the brain and spinal cord (central nervous system) and a network of branching nerves that travel throughout the body (peripheral nervous system). Some of the major nerves in the peripheral system are identified in this drawing.<\/em><\/figcaption><\/figure>\n\nSignals of the Nervous System<\/h2>\n<\/div>\n
The signals sent by the nervous system are electrical signals called\u00a0nerve impulses<\/a><\/strong>, and they are transmitted by special nervous system\u00a0cells called\u00a0neurons<\/a><\/strong> (or nerve cells), like the one in Figure 8.2.3. Long projections (called axons) from neurons carry nerve impulses directly to specific target cells. A cell that receives nerve impulses from a neuron (typically a muscle or a gland) may be excited to perform a function, inhibited from carrying out an action, or otherwise controlled. In this way, the information transmitted by the nervous system is specific to particular cells and is transmitted very rapidly. In fact, the fastest nerve impulses travel at speeds greater than 100 metres per second! Compare this to the chemical messages carried by the hormones that are secreted into the blood by endocrine glands. These hormonal messages are \u201cbroadcast\u201d to all the cells of the body, and they can travel only as quickly as the blood flows through the cardiovascular system.<\/p>\nFigure 8.2.3 This model of a nerve cell shows part of its long axon which carries nerve impulses to other cells. The multiple shorter projections are called dendrites, and they receive nerve impulses from other cells.<\/em><\/figcaption><\/figure>\n\nThis simple model of a nerve cell shows part of its long axon which carries nerve impulses to other cells. The multiple shorter projections are called dendrites, and they receive nerve impulses from other cells.<\/p>\n<\/div>\n
Organization of the Nervous System<\/h2>\n
As you might predict, the human nervous system<\/a> is very complex. It has multiple divisions, beginning with its two main parts, the central nervous system<\/a> (CNS) and the peripheral nervous system<\/a> (PNS), as shown in the diagram below (Figure 8.2.4). The CNS includes the brain<\/a> and spinal cord<\/a>, and the PNS consists mainly of nerves<\/a><\/strong>, which are bundles of axons<\/a> from neurons. The nerves of the PNS connect the CNS to the rest of the body.<\/p>\nFigure 8.2.4 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.<\/figcaption><\/figure>\n\nThe PNS can be further subdivided into two divisions, known as the autonomic <\/a>and somatic nervous system<\/a>s (Figure 8.2.5<\/span>).\u00a0These divisions control different types of functions,\u00a0and they often interact with the CNS to carry out these functions. The somatic nervous system controls activities that are under voluntary<\/a> control, such as turning a steering wheel. The autonomic nervous system controls activities that are not under voluntary control<\/a>, such as digesting a meal. The autonomic nervous system has\u00a0three\u00a0main\u00a0divisions: the sympathetic division<\/a> (which controls the fight-or-flight response during emergencies), the parasympathetic division<\/a> (which controls the routine \u201chousekeeping\u201d functions of the body at other times),\u00a0and the enteric division<\/a> (which provides local control of the digestive system).\u00a0<\/span><\/p>\n<\/div>\nFigure 8.2.5 Divisions of the Nervous System. <\/em><\/figcaption><\/figure>\n <\/p>\n
\n\n\n8.2 Summary<\/span><\/h1>\n<\/header>\n\n\n- The nervous system<\/a> is the human organ system that coordinates all of the body\u2019s voluntary<\/a> and involuntary<\/a> actions, by transmitting signals to and from different parts of the body.<\/li>\n
- The nervous system has two major divisions, called the\u00a0central nervous system<\/a>\u00a0(CNS) and the\u00a0peripheral nervous system<\/a>\u00a0(PNS). The CNS\u00a0includes\u00a0the brain<\/a> and spinal cord<\/a>, and the PNS consists mainly of nerves<\/a>\u00a0that connect the CNS with the rest of the body.<\/li>\n
- The PNS\u00a0can be subdivided into\u00a0two major divisions: the somatic nervous system<\/a> and the autonomic nervous system<\/a>.The somatic system controls activities that are under voluntary control. The autonomic system controls activities that are not under voluntary control. The autonomic nervous system is further divided into the sympathetic division<\/a> (which controls the fight-or-flight response), the parasympathetic division<\/a> (which controls most routine involuntary responses),\u00a0and the enteric division<\/a> (which provides local control of the digestive system).<\/li>\n
- Electrical signals sent by the nervous system are called\u00a0nerve impulses<\/a>. They are transmitted by special\u00a0cells\u00a0called neurons<\/a>. Nerve impulses can travel to specific target cells very rapidly.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n
\n8.2 Review Questions<\/span><\/h1>\n<\/header>\n\n\n- List the general steps through which the nervous system generates\u00a0an appropriate response to information from the internal and external environments.<\/li>\n
- What are neurons?<\/li>\n
- Compare and contrast the central and peripheral nervous systems.<\/li>\n
- \n\n
Figure 8.2.5 Divisions of the Nervous System. <\/em>[\/caption]\r\n\r\n \r\n8.2 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- The [pb_glossary id=\"2908\"]nervous system[\/pb_glossary] is the human organ system that coordinates all of the body\u2019s [pb_glossary id=\"3004\"]voluntary[\/pb_glossary] and [pb_glossary id=\"3005\"]involuntary[\/pb_glossary] actions, by transmitting signals to and from different parts of the body.<\/li>\r\n \t
- The nervous system has two major divisions, called the\u00a0[pb_glossary id=\"5933\"]central nervous system[\/pb_glossary]\u00a0(CNS) and the\u00a0[pb_glossary id=\"3009\"]peripheral nervous system[\/pb_glossary]\u00a0(PNS). The CNS\u00a0includes\u00a0the [pb_glossary id=\"5915\"]brain[\/pb_glossary] and [pb_glossary id=\"3010\"]spinal cord[\/pb_glossary], and the PNS consists mainly of [pb_glossary id=\"3011\"]nerves[\/pb_glossary]\u00a0that connect the CNS with the rest of the body.<\/li>\r\n \t
- The PNS\u00a0can be subdivided into\u00a0two major divisions: the [pb_glossary id=\"3014\"]somatic nervous system[\/pb_glossary] and the [pb_glossary id=\"5899\"]autonomic nervous system[\/pb_glossary].The somatic system controls activities that are under voluntary control. The autonomic system controls activities that are not under voluntary control. The autonomic nervous system is further divided into the [pb_glossary id=\"3015\"]sympathetic division[\/pb_glossary] (which controls the fight-or-flight response), the [pb_glossary id=\"3016\"]parasympathetic division[\/pb_glossary] (which controls most routine involuntary responses),\u00a0and the [pb_glossary id=\"5987\"]enteric division[\/pb_glossary] (which provides local control of the digestive system).<\/li>\r\n \t
- Electrical signals sent by the nervous system are called\u00a0[pb_glossary id=\"5697\"]nerve impulses[\/pb_glossary]. They are transmitted by special\u00a0cells\u00a0called [pb_glossary id=\"2984\"]neurons[\/pb_glossary]. Nerve impulses can travel to specific target cells very rapidly.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n8.2 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- List the general steps through which the nervous system generates\u00a0an appropriate response to information from the internal and external environments.<\/li>\r\n \t
- What are neurons?<\/li>\r\n \t
- Compare and contrast the central and peripheral nervous systems.<\/li>\r\n \t
- [h5p id=\"553\"]<\/li>\r\n \t
- Which major division of the peripheral nervous system allows you to\u00a0walk to class? Which major division of the peripheral nervous system\u00a0controls your\u00a0heart\u00a0rate?<\/li>\r\n \t
- Identify the functions of the three\u00a0main\u00a0divisions of the autonomic nervous system.<\/li>\r\n \t
- [h5p id=\"554\"]<\/li>\r\n \t
- What is an axon, and what is its function?<\/li>\r\n \t
- Define nerve impulses.<\/li>\r\n \t
- Explain generally how the brain and spinal cord can interact with and control the rest of the body.<\/li>\r\n \t
- How are nerves and neurons related?<\/li>\r\n \t
- What type of information from the outside environment do you think is detected by sensory receptors in your ears?<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
\r\n8.2 Explore More<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=qPix_X-9t7E\r\nThe Nervous System, Part 1: Crash Course A&P #8, CrashCourse, 2015.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=Nsxw5_Iz7mY&feature=emb_logo\r\n
Engineering the Human Nervous System: Megan Moynahan at TEDxBrussels,\r\nTEDx Talks, 2013.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n \r\n\r\n<\/div>\r\n
Attributions<\/h2>\r\nFigure 8.2.1<\/strong>\r\n\r\nSkateboard_1613<\/a> by Autoria propia on Wikimedia Commons is released into the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain) (Derivative work of this file:\u00a0\u00a0SkateboardinDog.jpg)<\/a>\r\n\r\nFigure 8.2.2<\/strong>\r\n\r\nNervous_system_diagram.svg<\/a>\u00a0by\u00a0<\/span>The Emirr<\/a> on Wikimedia Commons is used under a\u00a0CC BY 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0\/deed.en) license.\r\n\r\nFigure 8.2.3<\/strong>\r\n\r\nMultipolarNeuron<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0\/deed.en) license.\r\n\r\nFigure 8.2.4<\/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 8.2.5<\/strong>\r\n\r\nDivisions of the Nervous System<\/a>\u00a0by CK-12 Foundation<\/a> is used under the CC BY-NC 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-nc\/3.0\/) license.\r\n \u00a9<\/span>CK-12 Foundation<\/a> Licensed under\u00a0<\/span><\/a>\u00a0\u2022\u00a0<\/span>Terms of Use<\/a>\u00a0\u2022\u00a0<\/span>Attribution<\/a><\/div>\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, April 25). Figure\u00a0<\/span>12.2<\/span>\u00a0<\/span>Central and peripheral nervous system <\/span>[digital image].\u00a0 In Anatomy and Physiology<\/em> (Section 12.1). OpenStax. https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/12-1-basic-structure-and-function-of-the-nervous-system<\/p>\r\nBrainard, J\/ CK-12 Foundation. (2016). Figure 5\u00a0 [digital image]. In CK-12 College Human Biology<\/em> (Section 10.2) [online Flexbook]. CK12.org. https:\/\/www.ck12.org\/book\/ck-12-college-human-biology\/section\/10.2\/<\/p>\r\nCrashCourse. (2015, February 23). The nervous system, Part 1: Crash Course A&P #8. YouTube. https:\/\/www.youtube.com\/watch?v=qPix_X-9t7E&feature=youtu.be<\/p>\r\n
TEDx Talks. (2013, November 3). Engineering the human nervous system: Megan Moynahan at TEDxBrussels. YouTube. https:\/\/www.youtube.com\/watch?v=Nsxw5_Iz7mY&feature=youtu.be<\/p>","rendered":"
<\/p>\nFigure 8.2.1 What would you do if this skateboarder suddenly appeared in front of your moving car?\u00a0<\/em><\/figcaption><\/figure>\nIn the Blink of an Eye<\/h1>\n
As you drive into a parking lot, a boy on a skateboard suddenly flies in front of your car across your field of\u00a0vision. You see the boy in the nick of time and react immediately. You slam on the brakes and steer sharply to the right \u2014 all in the blink of an eye. You avoid a collision, but just barely. You\u2019re shaken up, but thankful that no one was hurt. How did you respond so quickly? Rapid responses like this are controlled by your nervous system.<\/p>\n
\nOverview of the Nervous System<\/h1>\n<\/div>\n
The\u00a0nervous system<\/a><\/strong>, illustrated in the sketch below, is the human organ system that coordinates all of the body\u2019s voluntary<\/a> and involuntary<\/a> actions, by transmitting electrical signals to and from different parts of the body. Specifically, the nervous system extracts information from the internal and external environments, using sensory receptors<\/a>. Usually, it then\u00a0sends signals encoding this information to the brain<\/a>, which processes the information to determine an appropriate response. Finally, the brain sends signals to\u00a0muscles, organs<\/a>, or glands to bring about the response. In the example above, your\u00a0eyes\u00a0detected the boy, the information traveled to your brain, and your brain\u00a0told\u00a0your body to act so as to avoid a collision.<\/p>\nFigure 8.2.2 The human nervous system consists of the brain and spinal cord (central nervous system) and a network of branching nerves that travel throughout the body (peripheral nervous system). Some of the major nerves in the peripheral system are identified in this drawing.<\/em><\/figcaption><\/figure>\n\nSignals of the Nervous System<\/h2>\n<\/div>\n
The signals sent by the nervous system are electrical signals called\u00a0nerve impulses<\/a><\/strong>, and they are transmitted by special nervous system\u00a0cells called\u00a0neurons<\/a><\/strong> (or nerve cells), like the one in Figure 8.2.3. Long projections (called axons) from neurons carry nerve impulses directly to specific target cells. A cell that receives nerve impulses from a neuron (typically a muscle or a gland) may be excited to perform a function, inhibited from carrying out an action, or otherwise controlled. In this way, the information transmitted by the nervous system is specific to particular cells and is transmitted very rapidly. In fact, the fastest nerve impulses travel at speeds greater than 100 metres per second! Compare this to the chemical messages carried by the hormones that are secreted into the blood by endocrine glands. These hormonal messages are \u201cbroadcast\u201d to all the cells of the body, and they can travel only as quickly as the blood flows through the cardiovascular system.<\/p>\nFigure 8.2.3 This model of a nerve cell shows part of its long axon which carries nerve impulses to other cells. The multiple shorter projections are called dendrites, and they receive nerve impulses from other cells.<\/em><\/figcaption><\/figure>\n\nThis simple model of a nerve cell shows part of its long axon which carries nerve impulses to other cells. The multiple shorter projections are called dendrites, and they receive nerve impulses from other cells.<\/p>\n<\/div>\n
Organization of the Nervous System<\/h2>\n
As you might predict, the human nervous system<\/a> is very complex. It has multiple divisions, beginning with its two main parts, the central nervous system<\/a> (CNS) and the peripheral nervous system<\/a> (PNS), as shown in the diagram below (Figure 8.2.4). The CNS includes the brain<\/a> and spinal cord<\/a>, and the PNS consists mainly of nerves<\/a><\/strong>, which are bundles of axons<\/a> from neurons. The nerves of the PNS connect the CNS to the rest of the body.<\/p>\nFigure 8.2.4 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.<\/figcaption><\/figure>\n\nThe PNS can be further subdivided into two divisions, known as the autonomic <\/a>and somatic nervous system<\/a>s (Figure 8.2.5<\/span>).\u00a0These divisions control different types of functions,\u00a0and they often interact with the CNS to carry out these functions. The somatic nervous system controls activities that are under voluntary<\/a> control, such as turning a steering wheel. The autonomic nervous system controls activities that are not under voluntary control<\/a>, such as digesting a meal. The autonomic nervous system has\u00a0three\u00a0main\u00a0divisions: the sympathetic division<\/a> (which controls the fight-or-flight response during emergencies), the parasympathetic division<\/a> (which controls the routine \u201chousekeeping\u201d functions of the body at other times),\u00a0and the enteric division<\/a> (which provides local control of the digestive system).\u00a0<\/span><\/p>\n<\/div>\nFigure 8.2.5 Divisions of the Nervous System. <\/em><\/figcaption><\/figure>\n <\/p>\n
\n\n\n8.2 Summary<\/span><\/h1>\n<\/header>\n\n\n- The nervous system<\/a> is the human organ system that coordinates all of the body\u2019s voluntary<\/a> and involuntary<\/a> actions, by transmitting signals to and from different parts of the body.<\/li>\n
- The nervous system has two major divisions, called the\u00a0central nervous system<\/a>\u00a0(CNS) and the\u00a0peripheral nervous system<\/a>\u00a0(PNS). The CNS\u00a0includes\u00a0the brain<\/a> and spinal cord<\/a>, and the PNS consists mainly of nerves<\/a>\u00a0that connect the CNS with the rest of the body.<\/li>\n
- The PNS\u00a0can be subdivided into\u00a0two major divisions: the somatic nervous system<\/a> and the autonomic nervous system<\/a>.The somatic system controls activities that are under voluntary control. The autonomic system controls activities that are not under voluntary control. The autonomic nervous system is further divided into the sympathetic division<\/a> (which controls the fight-or-flight response), the parasympathetic division<\/a> (which controls most routine involuntary responses),\u00a0and the enteric division<\/a> (which provides local control of the digestive system).<\/li>\n
- Electrical signals sent by the nervous system are called\u00a0nerve impulses<\/a>. They are transmitted by special\u00a0cells\u00a0called neurons<\/a>. Nerve impulses can travel to specific target cells very rapidly.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n
\n8.2 Review Questions<\/span><\/h1>\n<\/header>\n\n\n- List the general steps through which the nervous system generates\u00a0an appropriate response to information from the internal and external environments.<\/li>\n
- What are neurons?<\/li>\n
- Compare and contrast the central and peripheral nervous systems.<\/li>\n
- \n\n
- \r\n \t
- The [pb_glossary id=\"2908\"]nervous system[\/pb_glossary] is the human organ system that coordinates all of the body\u2019s [pb_glossary id=\"3004\"]voluntary[\/pb_glossary] and [pb_glossary id=\"3005\"]involuntary[\/pb_glossary] actions, by transmitting signals to and from different parts of the body.<\/li>\r\n \t
- The nervous system has two major divisions, called the\u00a0[pb_glossary id=\"5933\"]central nervous system[\/pb_glossary]\u00a0(CNS) and the\u00a0[pb_glossary id=\"3009\"]peripheral nervous system[\/pb_glossary]\u00a0(PNS). The CNS\u00a0includes\u00a0the [pb_glossary id=\"5915\"]brain[\/pb_glossary] and [pb_glossary id=\"3010\"]spinal cord[\/pb_glossary], and the PNS consists mainly of [pb_glossary id=\"3011\"]nerves[\/pb_glossary]\u00a0that connect the CNS with the rest of the body.<\/li>\r\n \t
- The PNS\u00a0can be subdivided into\u00a0two major divisions: the [pb_glossary id=\"3014\"]somatic nervous system[\/pb_glossary] and the [pb_glossary id=\"5899\"]autonomic nervous system[\/pb_glossary].The somatic system controls activities that are under voluntary control. The autonomic system controls activities that are not under voluntary control. The autonomic nervous system is further divided into the [pb_glossary id=\"3015\"]sympathetic division[\/pb_glossary] (which controls the fight-or-flight response), the [pb_glossary id=\"3016\"]parasympathetic division[\/pb_glossary] (which controls most routine involuntary responses),\u00a0and the [pb_glossary id=\"5987\"]enteric division[\/pb_glossary] (which provides local control of the digestive system).<\/li>\r\n \t
- Electrical signals sent by the nervous system are called\u00a0[pb_glossary id=\"5697\"]nerve impulses[\/pb_glossary]. They are transmitted by special\u00a0cells\u00a0called [pb_glossary id=\"2984\"]neurons[\/pb_glossary]. Nerve impulses can travel to specific target cells very rapidly.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n 8.2 Review Questions<\/span><\/h1>\r\n<\/header>\r\n
\r\n- \r\n \t
- List the general steps through which the nervous system generates\u00a0an appropriate response to information from the internal and external environments.<\/li>\r\n \t
- What are neurons?<\/li>\r\n \t
- Compare and contrast the central and peripheral nervous systems.<\/li>\r\n \t
- [h5p id=\"553\"]<\/li>\r\n \t
- Which major division of the peripheral nervous system allows you to\u00a0walk to class? Which major division of the peripheral nervous system\u00a0controls your\u00a0heart\u00a0rate?<\/li>\r\n \t
- Identify the functions of the three\u00a0main\u00a0divisions of the autonomic nervous system.<\/li>\r\n \t
- [h5p id=\"554\"]<\/li>\r\n \t
- What is an axon, and what is its function?<\/li>\r\n \t
- Define nerve impulses.<\/li>\r\n \t
- Explain generally how the brain and spinal cord can interact with and control the rest of the body.<\/li>\r\n \t
- How are nerves and neurons related?<\/li>\r\n \t
- What type of information from the outside environment do you think is detected by sensory receptors in your ears?<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
\r\n 8.2 Explore More<\/span><\/h1>\r\n<\/header>\r\n
\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=qPix_X-9t7E\r\nThe Nervous System, Part 1: Crash Course A&P #8, CrashCourse, 2015.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=Nsxw5_Iz7mY&feature=emb_logo\r\n
Engineering the Human Nervous System: Megan Moynahan at TEDxBrussels,\r\nTEDx Talks, 2013.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n \r\n\r\n<\/div>\r\n
Attributions<\/h2>\r\nFigure 8.2.1<\/strong>\r\n\r\nSkateboard_1613<\/a> by Autoria propia on Wikimedia Commons is released into the public domain<\/a> (https:\/\/en.wikipedia.org\/wiki\/Public_domain) (Derivative work of this file:\u00a0\u00a0SkateboardinDog.jpg)<\/a>\r\n\r\nFigure 8.2.2<\/strong>\r\n\r\nNervous_system_diagram.svg<\/a>\u00a0by\u00a0<\/span>The Emirr<\/a> on Wikimedia Commons is used under a\u00a0CC BY 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0\/deed.en) license.\r\n\r\nFigure 8.2.3<\/strong>\r\n\r\nMultipolarNeuron<\/a> by BruceBlaus<\/a> on Wikimedia Commons is used under a CC BY 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/3.0\/deed.en) license.\r\n\r\nFigure 8.2.4<\/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 8.2.5<\/strong>\r\n\r\nDivisions of the Nervous System<\/a>\u00a0by CK-12 Foundation<\/a> is used under the CC BY-NC 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-nc\/3.0\/) license.\r\n
\u00a9<\/span>CK-12 Foundation<\/a> Licensed under\u00a0<\/span><\/a>\u00a0\u2022\u00a0<\/span>Terms of Use<\/a>\u00a0\u2022\u00a0<\/span>Attribution<\/a><\/div>\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, April 25). Figure\u00a0<\/span>12.2<\/span>\u00a0<\/span>Central and peripheral nervous system <\/span>[digital image].\u00a0 In Anatomy and Physiology<\/em> (Section 12.1). OpenStax. https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/12-1-basic-structure-and-function-of-the-nervous-system<\/p>\r\n
Brainard, J\/ CK-12 Foundation. (2016). Figure 5\u00a0 [digital image]. In CK-12 College Human Biology<\/em> (Section 10.2) [online Flexbook]. CK12.org. https:\/\/www.ck12.org\/book\/ck-12-college-human-biology\/section\/10.2\/<\/p>\r\n
CrashCourse. (2015, February 23). The nervous system, Part 1: Crash Course A&P #8. YouTube. https:\/\/www.youtube.com\/watch?v=qPix_X-9t7E&feature=youtu.be<\/p>\r\n
TEDx Talks. (2013, November 3). Engineering the human nervous system: Megan Moynahan at TEDxBrussels. YouTube. https:\/\/www.youtube.com\/watch?v=Nsxw5_Iz7mY&feature=youtu.be<\/p>","rendered":"
<\/p>\n
Figure 8.2.1 What would you do if this skateboarder suddenly appeared in front of your moving car?\u00a0<\/em><\/figcaption><\/figure>\n In the Blink of an Eye<\/h1>\n
As you drive into a parking lot, a boy on a skateboard suddenly flies in front of your car across your field of\u00a0vision. You see the boy in the nick of time and react immediately. You slam on the brakes and steer sharply to the right \u2014 all in the blink of an eye. You avoid a collision, but just barely. You\u2019re shaken up, but thankful that no one was hurt. How did you respond so quickly? Rapid responses like this are controlled by your nervous system.<\/p>\n
\nOverview of the Nervous System<\/h1>\n<\/div>\n
The\u00a0nervous system<\/a><\/strong>, illustrated in the sketch below, is the human organ system that coordinates all of the body\u2019s voluntary<\/a> and involuntary<\/a> actions, by transmitting electrical signals to and from different parts of the body. Specifically, the nervous system extracts information from the internal and external environments, using sensory receptors<\/a>. Usually, it then\u00a0sends signals encoding this information to the brain<\/a>, which processes the information to determine an appropriate response. Finally, the brain sends signals to\u00a0muscles, organs<\/a>, or glands to bring about the response. In the example above, your\u00a0eyes\u00a0detected the boy, the information traveled to your brain, and your brain\u00a0told\u00a0your body to act so as to avoid a collision.<\/p>\n
Figure 8.2.2 The human nervous system consists of the brain and spinal cord (central nervous system) and a network of branching nerves that travel throughout the body (peripheral nervous system). Some of the major nerves in the peripheral system are identified in this drawing.<\/em><\/figcaption><\/figure>\n \nSignals of the Nervous System<\/h2>\n<\/div>\n
The signals sent by the nervous system are electrical signals called\u00a0nerve impulses<\/a><\/strong>, and they are transmitted by special nervous system\u00a0cells called\u00a0neurons<\/a><\/strong> (or nerve cells), like the one in Figure 8.2.3. Long projections (called axons) from neurons carry nerve impulses directly to specific target cells. A cell that receives nerve impulses from a neuron (typically a muscle or a gland) may be excited to perform a function, inhibited from carrying out an action, or otherwise controlled. In this way, the information transmitted by the nervous system is specific to particular cells and is transmitted very rapidly. In fact, the fastest nerve impulses travel at speeds greater than 100 metres per second! Compare this to the chemical messages carried by the hormones that are secreted into the blood by endocrine glands. These hormonal messages are \u201cbroadcast\u201d to all the cells of the body, and they can travel only as quickly as the blood flows through the cardiovascular system.<\/p>\n
Figure 8.2.3 This model of a nerve cell shows part of its long axon which carries nerve impulses to other cells. The multiple shorter projections are called dendrites, and they receive nerve impulses from other cells.<\/em><\/figcaption><\/figure>\n \nThis simple model of a nerve cell shows part of its long axon which carries nerve impulses to other cells. The multiple shorter projections are called dendrites, and they receive nerve impulses from other cells.<\/p>\n<\/div>\n
Organization of the Nervous System<\/h2>\n
As you might predict, the human nervous system<\/a> is very complex. It has multiple divisions, beginning with its two main parts, the central nervous system<\/a> (CNS) and the peripheral nervous system<\/a> (PNS), as shown in the diagram below (Figure 8.2.4). The CNS includes the brain<\/a> and spinal cord<\/a>, and the PNS consists mainly of nerves<\/a><\/strong>, which are bundles of axons<\/a> from neurons. The nerves of the PNS connect the CNS to the rest of the body.<\/p>\n
Figure 8.2.4 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.<\/figcaption><\/figure>\n \nThe PNS can be further subdivided into two divisions, known as the autonomic <\/a>and somatic nervous system<\/a>s (Figure 8.2.5<\/span>).\u00a0These divisions control different types of functions,\u00a0and they often interact with the CNS to carry out these functions. The somatic nervous system controls activities that are under voluntary<\/a> control, such as turning a steering wheel. The autonomic nervous system controls activities that are not under voluntary control<\/a>, such as digesting a meal. The autonomic nervous system has\u00a0three\u00a0main\u00a0divisions: the sympathetic division<\/a> (which controls the fight-or-flight response during emergencies), the parasympathetic division<\/a> (which controls the routine \u201chousekeeping\u201d functions of the body at other times),\u00a0and the enteric division<\/a> (which provides local control of the digestive system).\u00a0<\/span><\/p>\n<\/div>\n
Figure 8.2.5 Divisions of the Nervous System. <\/em><\/figcaption><\/figure>\n <\/p>\n
\n\n\n 8.2 Summary<\/span><\/h1>\n<\/header>\n
\n- \n
- The nervous system<\/a> is the human organ system that coordinates all of the body\u2019s voluntary<\/a> and involuntary<\/a> actions, by transmitting signals to and from different parts of the body.<\/li>\n
- The nervous system has two major divisions, called the\u00a0central nervous system<\/a>\u00a0(CNS) and the\u00a0peripheral nervous system<\/a>\u00a0(PNS). The CNS\u00a0includes\u00a0the brain<\/a> and spinal cord<\/a>, and the PNS consists mainly of nerves<\/a>\u00a0that connect the CNS with the rest of the body.<\/li>\n
- The PNS\u00a0can be subdivided into\u00a0two major divisions: the somatic nervous system<\/a> and the autonomic nervous system<\/a>.The somatic system controls activities that are under voluntary control. The autonomic system controls activities that are not under voluntary control. The autonomic nervous system is further divided into the sympathetic division<\/a> (which controls the fight-or-flight response), the parasympathetic division<\/a> (which controls most routine involuntary responses),\u00a0and the enteric division<\/a> (which provides local control of the digestive system).<\/li>\n
- Electrical signals sent by the nervous system are called\u00a0nerve impulses<\/a>. They are transmitted by special\u00a0cells\u00a0called neurons<\/a>. Nerve impulses can travel to specific target cells very rapidly.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n
\n\n 8.2 Review Questions<\/span><\/h1>\n<\/header>\n
\n- \n
- List the general steps through which the nervous system generates\u00a0an appropriate response to information from the internal and external environments.<\/li>\n
- What are neurons?<\/li>\n
- Compare and contrast the central and peripheral nervous systems.<\/li>\n
- \n\n
- The nervous system has two major divisions, called the\u00a0central nervous system<\/a>\u00a0(CNS) and the\u00a0peripheral nervous system<\/a>\u00a0(PNS). The CNS\u00a0includes\u00a0the brain<\/a> and spinal cord<\/a>, and the PNS consists mainly of nerves<\/a>\u00a0that connect the CNS with the rest of the body.<\/li>\n
- The nervous system<\/a> is the human organ system that coordinates all of the body\u2019s voluntary<\/a> and involuntary<\/a> actions, by transmitting signals to and from different parts of the body.<\/li>\n
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