1. What helps you remember your part in a play?
The Nervous System
What helps you remember your part in a play?
Your nervous system.
It is a complex network that allows communication between the brain and all other areas of the body.

2. In this lesson, you will learn to:
Lesson Objectives
In this lesson, you will learn to:
Describe the structure and function of neurons
Examine the central nervous system, including the areas of the brain and the function of each
Examine the peripheral nervous system, including the steps of a reflex action

3. Function and Structure of the Nervous System
Your nervous system coordinates all of the activities in your body.
The nervous system has two main divisions, the central nervous system (CNS) and the peripheral nervous system (PNS).

4. Function and Structure of the Nervous System
Two Main Divisions of the Nervous System
The central nervous system consists of the brain and spinal cord.
It receives messages from the nerves in the peripheral nervous system, interprets them, and sends out a response.
CNS
PNS

5. Classification of Neurons
Messages are transmitted to and from the spinal cord and
brain by neurons.
Neurons are classified by their function into:
Sensory neurons
Motor neurons
Interneurons

6. Neurons
The Nerve Impulse
Click image to view animation.

7. Parts of a Neuron Neurons
A neuron consists of three main parts: the cell body, dendrites, and axons.
Cell Body
Dendrites
Axons
The cell body of a neuron contains the nucleus, the control center of the cell.
The nucleus regulates the production of proteins within the cell.
Neurons have limited ability to repair damage or replace destroyed cells.

8. The Central Nervous System
The Spinal Cord
The spinal cord is a long column of nerve tissue extending down your back.
Vertebrae are the bones that make up your spine.
Connective tissue called the spinal meninges, along with the vertebrae, help protect the spinal cord.
The spinal cord is also bathed in cerebrospinal fluid that absorbs shock and nourishes nerve tissue.

9. The Central Nervous System
Structure and Parts of the Spinal Cord

10. The Central Nervous System
The Brain
The brain integrates and controls the activities of the nervous system. It is involved in emotions and all of your senses.
The brain sits in the protective cavity formed by the bones of the skull.
It is covered with layers of cranial meninges and surrounded by cerebrospinal fluid. Both help protect the tissues of the brain from injury.
The brain has three main divisions: the cerebrum, the cerebellum, and the brain stem.

11. The Central Nervous System
Structure and Parts of the Brain

12. The Central Nervous System
The Cerebrum
The cerebrum is divided into two hemispheres that communicate with each other.
The left hemisphere is the center for language and reasoning; the right hemisphere is the center for processing music and art.
Each hemisphere has four lobes: the frontal lobe, the parietal lobe, the occipital lobe, and the temporal lobe.

13. The Central Nervous System
The Cerebellum
The cerebellum’s principal function is to coordinate the movement of skeletal muscles.
This area of the brain continually receives messages from sensory neurons in the inner ear and muscles, and it uses this information to maintain the body’s posture and balance.

14. The Central Nervous System
The Brain Stem
Incoming sensory impulses and outgoing motor impulses pass through the brain stem.
It consists of three main parts—the medulla oblongata, the pons, and the midbrain—and two smaller regions—the thalamus and the hypothalamus.

15. The Central Nervous System
Main Parts of the Brain Stem
Medulla oblongata: The medulla oblongata has centers that regulate heartbeat and respiratory rates as well as reflexes.
Pons: The pons is the pathway connecting nerve impulses to other areas of the brain.
Midbrain: The midbrain is involved in such functions as controlling eyeball movement and pupil size.

16. The Central Nervous System
Smaller Regions of the Brain Stem
Thalamus: The thalamus is an important relay center for incoming sensory impulses.
Nerve cells within the thalamus receive information from different sense organs.
Hypothalamus: The hypothalamus controls and balances various body processes to regulate body temperature, stimulate appetite for food and drink, and regulate sleep.
The hypothalamus also controls secretions from the pituitary gland.

17. The Peripheral Nervous System
What Is the PNS?
The peripheral nervous system (PNS) consists of all of the nerves that are not part of the CNS.
The PNS carries messages between the CNS and the rest of the body.
The PNS can be divided into two categories, the autonomic nervous system and the somatic nervous system.

18. The Peripheral Nervous System
The Autonomic Nervous System
The autonomic nervous system (ANS) controls many involuntary functions. The ANS consists of a network of nerves divided into two smaller networks: the sympathetic nervous system and the parasympathetic nervous system.
Sympathetic
Parasympathetic
This is the “fight or flight” response that prepares your body to react to a dangerous situation.
You also have experienced a reflex, when a doctor tests the knee-jerk reflex by tapping the ligament below the knee.

19. The Peripheral Nervous System
Steps of a Reflex Action
Click image to view animation.

20. The Peripheral Nervous System
Somatic Nervous System
The somatic nervous system consists of sensory neurons that relay messages from receptors to the CNS and motor neurons that carry impulses from the CNS to skeletal muscles.

21. Quick Review
Choose the appropriate option.
Q. The main function of the brain is to integrate and control the activities of the nervous system.
True
False

22. Quick Review - Answer
A. False. Every physical activity session should include a warm-up, a workout, and a cool-down.
Click Next to attempt another question.

23. Q. The parts of a neuron include:
Quick Review
Choose the appropriate option.
Q. The parts of a neuron include:
Cell Body
Dendrites
Axons
All of the above

24. A. 4. All of the above Quick Review - Answer
Neurons, or nerve cells, transmit messages from the brain to the spinal cord.
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25. Q. A reflex is a spontaneous response of the body to a stimulus.
Quick Review
Choose the appropriate option.
Q. A reflex is a spontaneous response of the body to a stimulus.
True
False

26. A. True. Reflexes allow you to withdraw from dangerous situations.
Quick Review - Answer
A. True. Reflexes allow you to withdraw from dangerous situations.
Click Next to attempt another question.

27. End of Lesson 4
Click Home to view the Main menu.

28. Function and Structure of the Nervous System
Two Main Divisions of the Nervous System
The peripheral nervous system gathers information from inside and outside your body.
It includes nerves that extend from the brain, spinal cord, and sensory receptors, such as those in the skin that sense pressure, temperature, or pain.
CNS
PNS

29. Parts of a Neuron Neurons
A neuron consists of three main parts: the cell body, dendrites, and axons.
Cell Body
Dendrites
Axons
Dendrites are branched structures that extend from the cell body in most neurons.
Dendrites receive information from other neurons or sensory receptors and transmit impulses toward the cell body.

30. Parts of a Neuron Neurons
A neuron consists of three main parts: the cell body, dendrites, and axons.
Cell Body
Dendrites
Axons
Axons transmit impulses away from the cell body and toward another neuron, muscle cell, or gland.
Some axons are surrounded by a covering called a myelin sheath and can transmit impulses more quickly than axons without coverings.

31. The Peripheral Nervous System
The Autonomic Nervous System
The autonomic nervous system (ANS) controls many involuntary functions. The ANS consists of a network of nerves divided into two smaller networks: the sympathetic nervous system and the parasympathetic nervous system.
Sympathetic Nervous System
Sympathetic
Parasympathetic
During periods of rest and relaxation, the parasympathetic system opposes the action of the sympathetic system by slowing body functions.
It slows down the heartbeat, opens blood vessels, and lowers blood pressure.
This is the “fight or flight” response that
prepares your body to react to a dangerous
situation.
You also have experienced a reflex, when a
doctor tests the knee-jerk reflex by tapping
the ligament below the knee.

32. Classification of Neurons
Messages are transmitted to and from the spinal cord and
brain by neurons.
Neurons are classified by their function into:
Sensory neurons
Motor neurons
Interneurons
A neuron is a nerve cell.

33. The Central Nervous System
The Brain
The brain integrates and controls the activities of the nervous system. It is involved in emotions and all of your senses.
The brain sits in the protective cavity formed by the bones of the skull.
It is covered with layers of cranial meninges and surrounded by cerebrospinal fluid. Both help protect the tissues of the brain from injury.
The brain has three main divisions: the cerebrum, the cerebellum, and the brain stem.
The cerebrum is the largest and most complex part of the brain.

34. The Central Nervous System
The Brain
The brain integrates and controls the activities of the nervous system. It is involved in emotions and all of your senses.
The brain sits in the protective cavity formed by the bones of the skull.
It is covered with layers of cranial meninges and surrounded by cerebrospinal fluid. Both help protect the tissues of the brain from injury.
The brain has three main divisions: the cerebrum, the cerebellum, and the brain stem.
The cerebellum is the second largest part of the brain.

35. The Central Nervous System
The Brain
The brain integrates and controls the activities of the nervous system. It is involved in emotions and all of your senses.
The brain sits in the protective cavity formed by the bones of the skull.
It is covered with layers of cranial meninges and surrounded by cerebrospinal fluid. Both help protect the tissues of the brain from injury.
The brain has three main divisions: the cerebrum, the cerebellum, and the brain stem.
The brain stem is a three-inch stalk of nerve cells and fibers that connects the spinal cord to the rest of the brain.

36. The Peripheral Nervous System
The Autonomic Nervous System
The autonomic nervous system (ANS) controls many involuntary functions. The ANS consists of a network of nerves divided into two smaller networks: the sympathetic nervous system and the parasympathetic nervous system.
A reflex is a spontaneous response of the body to a stimulus.
Sympathetic
Parasympathetic
This is the “fight or flight” response that prepares your body to react to a dangerous situation.
You also have experienced a reflex, when a doctor tests the knee-jerk reflex by tapping the ligament below the knee.

37. Quick Review - Answer
A. Correct! The brain helps you receive and process messages; think, remember, and reason; and coordinate muscle movements.
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38. Quick Review - Answer
You have answered the question incorrectly. Go back to try again, or click Next to view the correct answer.

39. Quick Review - Answer
A. Correct! Neurons, or nerve cells, transmit messages from the brain to the spinal cord.
Click Next to attempt another question.

40. Quick Review - Answer
You have answered the question incorrectly. Go back to try again, or click Next to view the correct answer.

41. A. Correct! Reflexes allow you to withdraw from dangerous situations.
Quick Review - Answer
A. Correct! Reflexes allow you to withdraw from dangerous situations.
Click Next to attempt another question.

42. Quick Review - Answer
You have answered the question incorrectly. Go back to try again, or click Next to view the correct answer.