The Nervous System
Lesson 4
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.
Lesson Objectives
Lesson 4
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
Function and Structure of the Nervous System
Lesson 4
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).
Function and Structure of the Nervous System
Lesson 4
Two Main Divisions of the Nervous System
The central nervous system
consists of the brain and spinal
CNS cord.
It receives messages from
the nerves in the peripheral
nervous system, interprets
them, and sends out a
PNS response.
Neurons
Lesson 4
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
Neurons
Lesson 4
The Nerve Impulse
Click image to view animation.
Neurons
Lesson 4
Parts of a Neuron
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.
The Central Nervous System
Lesson 4
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.
The Central Nervous System
Lesson 4
Structure and Parts of the Spinal Cord
The Central Nervous System
Lesson 4
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 Central Nervous System
Lesson 4
Structure and Parts of the Brain
The Central Nervous System
Lesson 4
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.
The Central Nervous System
Lesson 4
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.
The Central Nervous System
Lesson 4
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.
The Central Nervous System
Lesson 4
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.
The Central Nervous System
Lesson 4
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.
The Peripheral Nervous System
Lesson 4
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.
The Peripheral Nervous System
Lesson 4
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.
The Peripheral Nervous System
Lesson 4
Steps of a Reflex Action
Click image to view animation.
The Peripheral Nervous System
Lesson 4
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.
Quick Review
Lesson 4
Choose the appropriate option.
Q. The main function of the brain is True
to integrate and control the
activities of the nervous system. False
Quick Review - Answer
Lesson 4
A. False. Every physical activity session should include a
warm-up, a workout, and a cool-down.
Click Next to attempt another question.
Quick Review
Lesson 4
Choose the appropriate option.
Q. The parts of a neuron include: 1. Cell Body
2. Dendrites
3. Axons
4. All of the above
Quick Review - Answer
Lesson 4
A. 4. All of the above
Neurons, or nerve cells, transmit messages from the
brain to the spinal cord.
Click Next to attempt another question.
Quick Review
Lesson 4
Choose the appropriate option.
Q. A reflex is a spontaneous True
response of the body to a
stimulus.
False
Quick Review - Answer
Lesson 4
A. True. Reflexes allow you to withdraw from dangerous
situations.
Click Next to attempt another question.
Lesson 4
End of Lesson 4
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Function and Structure of the Nervous System
Lesson 4
Two Main Divisions of the Nervous System
The peripheral nervous system
gathers information from inside
CNS 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
PNS pressure, temperature, or pain.
Neurons
Lesson 4
Parts of a Neuron
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.
Neurons
Lesson 4
Parts of a Neuron
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.
The Peripheral Nervous System
Lesson 4
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
Sympathetic Parasympathetic
Nervous System
During “fight or flight” response that
This is the periods of rest and relaxation,
the parasympathetic system dangerous
prepares your body to react to aopposes
the action of the sympathetic system by
situation.
slowing body functions.
You also have experienced a reflex, when a
It slows the knee-jerk reflex by tapping
doctor testsdown the heartbeat, opens
theblood vessels, and lowers blood
ligament below the knee.
pressure.
Neurons
Lesson 4
Classification of Neurons
Messages are transmitted to and from the spinal cord and
brain by neurons.
A
Neurons are classified by their function into:
neuron is a
nerve
• Sensory neurons cell.
• Motor neurons
• Interneurons
The Central Nervous System
Lesson 4
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. The
cerebrum is the
• It is covered with layers of cranial meninges and surrounded
largest and most
by cerebrospinal fluid. Both help protect the tissues of the
complex part of
brain from injury. the brain.
• The brain has three main divisions: the cerebrum, the
cerebellum, and the brain stem.
The Central Nervous System
Lesson 4
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.
The
cerebellum is
• It is covered with layers of cranial meninges and surrounded
the second
by cerebrospinal fluid. Both help protect the tissues of the
largest part ofinjury.
brain from
the brain.
• The brain has three main divisions: the cerebrum, the
cerebellum, and the brain stem.
The Central Nervous System
Lesson 4
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 brain stem
the skull.
is a three-inch stalk
• It isof nerve cells and
covered with layers of cranial meninges and surrounded
fibers that connects
by cerebrospinal fluid. Both help protect the tissues of the
the spinal cord
brain from injury. to
the rest of the brain.
• The brain has three main divisions: the cerebrum, the
cerebellum, and the brain stem.
The Peripheral Nervous System
Lesson 4
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
Sympathetic Parasympathetic
spontaneous
response of the
This is the “fight or flight” response that
body to a
prepares your body to react to a dangerous
situation. stimulus.
You also have experienced a reflex, when
a doctor tests the knee-jerk reflex by
tapping the ligament below the knee.
Quick Review - Answer
Lesson 4
A. Correct! The brain helps you receive and process
messages; think, remember, and reason; and coordinate
muscle movements.
Click Next to attempt another question.
Quick Review - Answer
Lesson 4
You have answered the question incorrectly. Go back to try
again, or click Next to view the correct answer.
Quick Review - Answer
Lesson 4
A. Correct! Neurons, or nerve cells, transmit messages from
the brain to the spinal cord.
Click Next to attempt another question.
Quick Review - Answer
Lesson 4
You have answered the question incorrectly. Go back to try
again, or click Next to view the correct answer.
Quick Review - Answer
Lesson 4
A. Correct! Reflexes allow you to withdraw from dangerous
situations.
Click Next to attempt another question.
Quick Review - Answer
Lesson 4
You have answered the question incorrectly. Go back to try
again, or click Next to view the correct answer.