1. Section 1: Structures of the Nervous System
Preview
Bellringer
Key Ideas
Central Nervous System
Peripheral Nervous System
The Spinal Reflex
Summary

2. Bellringer
Make a list of behaviors that you think are reflexive behaviors.
Which of these behaviors, if any, do you think require conscious thought?

3. Key Ideas What is the function of the central nervous system?
What are the two components of the peripheral nervous system?
How is a spinal reflex generated?

4. Central Nervous System
The nervous system is an organized network of nerve cells called neurons which communicate with each other and with muscles and glands.
The signals of the nervous system are both electrical and chemical.
The nervous system is divided into two main systems called the central nervous system and the peripheral nervous system.

5. Central Nervous System, continued
The central nervous system (CNS) contains the brain and spinal cord and is considered the main control network of the body.
The central nervous system responds to internal and external information.
The peripheral nervous system (PNS) branches throughout the body and contains all of the parts of the nervous system except the brain and spinal cord.

6. Central Nervous System, continued
The PNS has sensory neurons and motor neurons which are responsible for communicating between the CNS and the rest of the body.
Sensory neurons send information from the sense organs, such as the skin, to the CNS.
Motor neurons send commands from the CNS to muscles and other organs, such as glands.

7. Visual Concept: Anatomy of the Human Nervous System

8. Central Nervous System, continued
The brain contains about 100 billion neurons and is the main processing center of the entire nervous system.
The brain is divided into several parts including the cerebrum, the thalamus, the hypothalamus, the brainstem, and the cerebellum.
The large upper part of the brain is called the cerebrum. The cerebrum controls movement and receives sensations.

9. The Cerebrum

10. Central Nervous System, continued
The folded outer surface of the cerebrum is called the cerebral cortex, or simply the cortex.
The cerebrum is divided into two hemispheres which communicate through a connecting band of nerves called the corpus callosum.
The left cerebral hemisphere receives sensations from and controls movements of the right side of the body. The right cerebral hemisphere receives sensations from and controls movements of the left side of the body.

11. Visual Concept: Cerebrum

12. Central Nervous System, continued
The thalamus and hypothalamus are two structures in the brain located below the cerebrum.
The thalamus is a critical site for processing and relaying sensory information from all parts of the body.
The hypothalamus controls feelings of hunger and thirst and regulates body temperature. The hypothalamus also helps regulate the endocrine system by controlling the secretion of many hormones.

13. Visual Concept: Parts of the Human Brain

14. Central Nervous System, continued
At the base of the brain is a stemlike structure called the brainstem which connects the two cerebral hemispheres with the spinal cord.
The brainstem consists of the midbrain, the pons, and the medulla oblongata. These structures maintain homeostasis by regulating heart rate and breathing rate.
Located behind the brainstem is the cerebellum which regulates balance, posture, and movement.

15. Visual Concept: Cerebellum

16. Central Nervous System, continued
The spinal cord is a column of nerve tissue that runs from the base of the brain through the vertebral column and links the brain to most of the PNS.
Information travels up and down through the spinal cord to maintain and control the body.
The spinal cord is linked to the PNS through paired spinal nerves. Each spinal nerve has a dorsal (back) root and a ventral (front) root.

17. Visual Concept: Comparing Sensory and Motor Neurons

18. The Spinal Cord

19. Peripheral Nervous System
The peripheral nervous system contains sensory and motor neurons that carry information between the central nervous system and the rest of the body.
The peripheral nervous system is divided into two independent systems called the autonomic nervous system and the somatic nervous system.
The autonomic nervous system controls muscles which do not require our conscious control. This system is subdivided into the parasympathetic and sympathetic divisions.

20. Peripheral Nervous System, continued
The parasympathetic division restores normal conditions after a change, such as stimulating digestion after a meal or slowing the heart rate after exercise.
The sympathetic division controls the “fight-or-flight” response that occurs in a stressful situation.
The somatic nervous system controls muscles which are under conscious control, such as the leg muscles used to walk across a room.

21. Visual Concept: Comparing the Somatic and Autonomic Nervous Systems

22. The Spinal Reflex
A reflex is a very fast, involuntary movement in response to a stimulus.
A spinal reflex is an involuntary movement triggered by sensory input and produced by neural circuitry limited to the spinal cord.
The knee-jerk reflex is a familiar example of a spinal reflex.

23. Visual Concept: Reflex

24. Summary
The central nervous system responds to internal and external information.
The peripheral nervous system contains sensory and motor neurons that carry information between the central nervous system and the rest of the body.
A spinal reflex is an involuntary movement triggered by sensory input and produced by neural circuitry limited to the spinal cord.