Concept Practice
Divisions of the Nervous System

Chapter 111. Divisions of the Nervous System

autonomic nervous system
the part of the peripheral nervous system that regulates the internal organs
brain
largest part of the central nervous system; consists of about 80 billion neurons organized into networks for processing sensory information, storing memories, and controlling behavior
central nervous system (CNS)
the spinal cord and the brain
nerves
bundles of axons from thousands of neurons; make up the peripheral nervous system
nervous system
the body’s fast communication system, consisting of billions of neurons; divided into the peripheral and central nervous systems
neuron
a single nerve cell, forming the basis of the nervous system
parasympathetic division
the part of the autonomic nervous system that calms the body after a stressful event has passed
peripheral nervous system (PNS)
the sensory and motor neurons outside the brain and spinal cord
somatic nervous system
the part of the peripheral nervous system that carries sensory information and controls body movements
spinal cord
the part of the central nervous system that extends downward from the brain through the spine
sympathetic division
the part of the autonomic nervous system that arouses the body for action
Divisions of the Nervous System
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The image includes two human figures and a flow chart. The figure on the left is labeled Peripheral Nervous System and has the nerves of the body colored. The figure on the right is labeled Central Nervous System and has the brain and spinal cord colored. The flow chart starts with the nervous system and is represented by the following bulleted list: Nervous system the first level central nervous system - includes the spinal cord and brain the first level peripheral nervous system - includes the rest of the body the second level somatic nervous system - includes bodily sensations and control of movements the second level autonomic nervous system - includes self-regulated control of internal organs the third level parasympathetic nervous system - calms the body the third level sympathetic nervous system - arouses the body.
Learning Objectives:

Describe the relationships among the divisions and subdivisions of the nervous system.

Identify the main functions of each portion of the nervous system.

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The image is a human figure with the brain, spinal cord, and nerves of the body colored. The Central Nervous System is colored brown, which includes the brain and spinal cord. The Peripheral Nervous System is colored blue and red, which includes the nerves throughout the body.

1. The nervous system is the human body’s fast communication system. It consists of the central nervous system (brain and spinal cord) and the peripheral nervous system (all the other nerves in the body). In all, the nervous system contains around 85 billion individual nerve cells called neurons.

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The image is a simple flow chart. The Nervous System is comprised of two systems, the central nervous system and peripheral nervous systems. These two systems are joined by a double-headed arrow.

2. The central nervous system (often referred to as the CNS) includes most of the neurons in the body. It handles the information-processing and decision-making tasks. Sensory information from the outside world and from inside the body is channeled through the peripheral nervous system (PNS) and gets analyzed in the CNS. If some action is required, the CNS organizes a response and communicates the message through the peripheral nervous system to the appropriate muscles or internal organs.

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The image is a human figure with the brain, spinal cord, and nerves of the body colored. The Somatic Divison is colored blue and includes the nerves connecting the skin and muscles to the spinal cord and brain. The Autonomic Division is colored red and includes the nerves connecting the major bodily organs to the spinal cord and brain.

3. The peripheral nervous system is subdivided into the somatic nervous system (which carries sensory messages from skin and muscles, and controls the body’s movements) and the autonomic nervous system (which communicates with and regulates the internal organs, largely outside conscious awareness).

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The image includes a figure of a man's body with his brain and spinal cord visible. There are lines coming from different areas on the spinal cord corresponding to different parts of the body. On the left side of the man is a list of body parts relating to the sympathetic division. This list includes the following body parts dispersed between the upper and lower back on the spinal cord: eye, heart, stomach and pancreas, liver, adrenal gland and kidney, bladder, and genitals. On the right side of the man is a list of body parts relating to the parasympathetic division. This list includes the following body parts linked to the top of the spinal cord: eye, heart, stomach and pancreas, and liver. The bladder and genitals are linked to the bottom of the spinal cord.

4. The autonomic nervous system (sometimes referred to as the ANS) controls the glands and muscles of our internal organs. It regulates the automatic behaviors necessary for survival. (Autonomic means "self-regulating.") The autonomic nervous system has two subdivisions, one responsible for mobilizing us during stressful situations, and the other for calming us when the emergency has passed.

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The image includes a figure of a man's body with his brain and spinal cord visible. There are lines coming from different areas on the spinal cord corresponding to different parts of the body. On the left side of the man is a list of body parts relating to the sympathetic division. This list includes the following body parts dispersed between the upper and lower back on the spinal cord: eye, heart, stomach and pancreas, liver, adrenal gland and kidney, bladder, and genitals. On the right side of the man is a list of body parts relating to the parasympathetic division. This list includes the following body parts linked to the top of the spinal cord: eye, heart, stomach and pancreas, and liver. The bladder and genitals are linked to the bottom of the spinal cord.

5. The sympathetic division of the autonomic nervous system arouses the body during emergencies by accelerating heartbeat, slowing digestion, raising blood sugar, dilating arteries, and creating perspiration. This prepares the body for an energetic physical response to a threat or challenge, including the challenge of sexual intercourse.

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The image includes a figure of a man's body with his brain and spinal cord visible. There are lines coming from different areas on the spinal cord corresponding to different parts of the body. On the left side of the man is a list of body parts relating to the sympathetic division. This list includes the following body parts dispersed between the upper and lower back on the spinal cord: eye, heart, stomach and pancreas, liver, adrenal gland and kidney, bladder, and genitals. On the right side of the man is a list of body parts relating to the parasympathetic division. This list includes the following body parts linked to the top of the spinal cord: eye, heart, stomach and pancreas, and liver. The bladder and genitals are linked to the bottom of the spinal cord.

6. The parasympathetic division of the autonomic nervous system relaxes the body after the emergency has passed, by producing the opposite effects—slowing the heartbeat, stimulating digestion, lowering blood sugar, contracting the arteries, and shutting down perspiration. The parasympathetic system is also responsible for the localized sexual arousal of the genitals in both females and males. Although this connection to sexual arousal may seem an exception to the usual tendency of the parasympathetic division to calm the body, it makes sense in terms of survival—having engorged genitals would not be a useful response in the presence of danger, when the sympathetic division is activated.

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The image includes a figure of a man's body with his brain and spinal cord visible. There are lines coming from different areas on the spinal cord corresponding to different parts of the body. On the left side of the man is a list of body parts relating to the sympathetic division. This list includes the following body parts dispersed between the upper and lower back on the spinal cord: eye, heart, stomach and pancreas, liver, adrenal gland and kidney, bladder, and genitals. On the right side of the man is a list of body parts relating to the parasympathetic division. This list includes the following body parts linked to the top of the spinal cord: eye, heart, stomach and pancreas, and liver. The bladder and genitals are linked to the bottom of the spinal cord.

7. Here’s a memory aid—a sentence that may help you remember the general functions (except for sexual responses) of the two parts of the autonomic nervous system: The sympathetic division makes you sizzle (arouses you for action); the parasympathetic division pacifies you (calms you down).

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Practice: Exploring the Nervous System

Roll over each part of the nervous system to see a brief description.

nervous system

central nervous system (CNS)

brain

spinal cord

peripheral nervous system (PNS)

somatic nervous system

autonomic nervous system

sympathetic division

parasympathetic division

Description:

nervous system: the body’s fast communication system, consisting of billions of neurons; divided into the peripheral and central nervous systems

central nervous system (CNS): the spinal cord and the brain

brain: largest part of the central nervous system; consists of about 80 billion neurons organized into networks for processing sensory information, storing memories, and controlling behavior

spinal cord: the part of the central nervous system that extends downward from the brain through the spine

peripheral nervous system (PNS): the sensory and motor neurons outside the brain and spinal cord

somatic nervous system: the part of the peripheral nervous system that carries sensory information and controls body movements

autonomic nervous system: the part of the peripheral nervous system that regulates the internal organs

sympathetic division: the part of the autonomic nervous system that arouses the body for action

parasympathetic division: the part of the autonomic nervous system that calms the body after a stressful event has passed

dnd_test

Quiz 1

Drag the label for each of the parts of the nervous system into the correct location on this chart. When all the labels have been placed, select the CHECK ANSWER button.

Select the NEXT button and move to Quiz 2.
Perhaps you should go back to review the divisions of the nervous system.
Nervous system
Central nervous system
Peripheral nervous system
Brain
Spinal cord
Somatic nervous system
Autonomic nervous system
Sympathetic division
Parasympathetic division
matching_test

Quiz 2

Match the parts of the nervous system with their descriptions by dragging each colored circle to the appropriate gray circle. When all the circles have been placed, select the CHECK ANSWER button.

Select the NEXT button and move to the Conclusion.
Perhaps you should go back to review the divisions of the nervous system.
peripheral nervous system (PNS)
parasympathetic division
autonomic nervous system
sympathetic division
nervous system
somatic nervous system
central nervous system (CNS)
neuron
the part of the peripheral nervous system that regulates the internal organs
the spinal cord and the brain
the body’s fast communication system, consisting of billions of neurons; divided into the peripheral and central nervous systems
a single nerve cell, forming the basis of the nervous system
the part of the autonomic nervous system that calms the body after a stressful event has passed
the sensory and motor neurons outside the brain and spinal cord
the part of the peripheral nervous system that carries sensory information and controls body movements
the part of the autonomic nervous system that arouses the body for action
end_slide
The image includes two human figures and a flow chart. The figure on the left is labeled Peripheral Nervous System and has the nerves of the body colored. The figure on the right is labeled Central Nervous System and has the brain and spinal cord colored. The flow chart starts with the nervous system and is represented by the following bulleted list: Nervous system the first level central nervous system - includes the spinal cord and brain the first level peripheral nervous system - includes the rest of the body the second level somatic nervous system - includes bodily sensations and control of movements the second level autonomic nervous system - includes self-regulated control of internal organs the third level parasympathetic nervous system - calms the body the third level sympathetic nervous system - arouses the body.
Congratulations!
You have completed the activity Divisions of the Nervous System.