Section 11.3 Your Nervous System
Your Nervous System
I can…
Describe the roles of the central nervous
system and the peripheral nervous system.
Identify the most important thing you can do to
keep your nervous system healthy.
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Section 11.3 Your Nervous System
Health Stats This graph compares bicycle-helmet use and seatbelt use among teens.
Why do you think many more teens wear seat belts
than bicycle helmets?
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Section 11.3 Your Nervous System
What Is the Nervous System?
• Your nervous system receives information about
what is going on inside and outside of your body.
• Then it processes the information and forms a
response to it.
• *The basic unit of the nervous system is a type of
cell called a neuron (NOOR ahn).
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Section 11.3 Your Nervous System
Neuron Structure
• Neurons carry messages, or impulses, from one part
of your body to another.
• A neuron has three basic parts.
• dendrites
• a cell body
• an axon
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Section 11.3 Your Nervous System
Types of Neurons
• Sensory Neurons Information about your external
and internal environment is gathered by sensory
neurons through your sense organs or other parts of
your body.
• Interneurons Located only in the brain and spinal
cord, interneurons pass impulses from one neuron to
another.
• Motor Neurons Motor neurons send nerve
impulses to muscles and glands.
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Section 11.3 Your Nervous System
Dendrite
Dendrites carry nerve
impulses toward a
neuron’s cell body.
Cell Body
The cell body controls
the cell’s basic functions.
Axon
Impulses travel along
axons toward other cells.
Myelin Sheath
Some axons are covered
by a myelin sheath
that increases the speed
of an impulse.
Neuron Structure
Synapse
The junction between
an axon and another
cell is a synapse.
Chemicals called
neurotransmitters pass
the impulse from the
sending neuron to the
receiving cell.
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Section 11.3 Your Nervous System
Central Nervous System
• The nervous system consists of two major
divisions—the central nervous system and the
peripheral nervous system.
• *The central nervous system is the control center of
the body. It includes the brain and spinal cord.
• *The peripheral nervous system includes all the
other parts of the nervous system.
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Section 11.3 Your Nervous System
The Brain
• The cerebrum consists of several specialized
regions that receive messages from sense organs,
and control movement, memory, communication, and
reasoning.
• The cerebellum (sehr uh BEL um) coordinates your
body’s movements and helps you keep your
balance.
• The brain stem consists of three structures—the
midbrain, pons, and medulla. These structures
control many of your body’s involuntary actions.
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Section 11.3 Your Nervous System
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Section 11.3 Your Nervous System
Mixed Messages
Test how well your brain can handle conflicting messages.
Material
watch or clock with second hand
Try This
Read the list of words while your partner times how long
it takes you.
Notice that the words in the list are written in different
colors. This time you should say the color of each word
as your partner times you. Do not read the words,
rather, identify their colors.
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Section 11.3 Your Nervous System
Mixed Messages
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Section 11.3 Your Nervous System
Mixed Messages
Think and Discuss
Did it take you more time to read the words or say the colors?
Describe the experience of saying the colors.
Which part of your brain most likely works hardest during this
activity? Which task is your brain better at—reading the words
or identifying their colors?
Once people master basic skills such as tying shoes or
reading, they perform them with little thought. How do you
think this fact affected your results in this activity?
What do you think would happen if you asked a young child
who has just learned to read to do this activity? Explain.
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Section 11.3 Your Nervous System
The Spinal Cord
• *The spinal cord is a thick column of nerve tissue
that links the brain to most of the nerves in the
peripheral nervous system.
• The spinal cord extends from the brain down the
back.
• Spinal nerves are part of the peripheral nervous
system.
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Section 11.3 Your Nervous System
Reflexes
• An automatic response to your environment is called
a reflex.
• In some reflex actions, the actions of the skeletal
muscles are controlled by the spinal cord only—not
the brain.
• Reflexes help protect your body from harm because
they enable you to react very quickly.
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Section 11.3 Your Nervous System
Sensory neurons in your
hand send impulses
to your spinal cord.
A Reflex Action
Neurons in your spinal
cord process the
information and send
commands directly
to motor neurons that
control muscles in your
arm and hand.
Your muscles contract and
you quickly withdraw your hand.
Meanwhile, messages of pain travel
to the brain. Shortly after your arm
moves, you feel pain.
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Section 11.3 Your Nervous System
Peripheral Nervous System
• *The peripheral nervous system includes the network
of nerves that links the rest of your body to your
brain and spinal cord.
• *The peripheral nervous system carries information
to the central nervous system, and then carries
responses from the central nervous system to the
rest of the body.
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Section 11.3 Your Nervous System
Sensory Division
• Some nerves in the sensory division carry
information about your outside environment from
your ears, eyes, and other sense organs.
• Other sensory nerves carry information about
internal body conditions such as blood pressure and
heart rate.
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Section 11.3 Your Nervous System
Motor Division
• Somatic Nervous System Motor nerves in the
somatic nervous system carry signals that control
voluntary actions.
• Autonomic Nervous System Motor nerves in the
autonomic nervous system regulate actions that
happen automatically.
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Section 11.3 Your Nervous System
1
2
1) Brain
2) Spinal cord
3) Peripheral nerves
3
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Section 11.3 Your Nervous System
Keeping Healthy
• Rest, good nutrition, and daily exercise can help
keep your nervous system functioning properly.
• *The most important step you can take to care for
your nervous system is to protect it from injury.
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Section 11.3 Your Nervous System
Avoiding Head Injuries
• A bruiselike injury to the brain is known as a
concussion.
• A coma is a prolonged period of deep
unconsciousness.
• Head injuries can be avoided.
• Wear a helmet when you play contact sports.
• Fasten your seat belt.
• Before diving into water be sure that it is deep
enough and that there are no underwater
hazards.
• Avoid drugs and alcohol.
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Section 11.3 Your Nervous System
Avoiding Spinal Cord Injuries
• Paralysis is the loss of the ability to move and feel
some part of the body.
• Spinal cord injuries can be avoided
• Fasten your seat belt.
• Take care when diving.
• Avoid drugs and alcohol.
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Section 11.3 Your Nervous System
Avoiding Nerve Injuries
• Individual peripheral nerves also can be injured.
• To help prevent carpal tunnel syndrome and similar
nerve injuries, it is important to take breaks from
repetitive motions and to maintain good posture.
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Section 11.3 Your Nervous System
Preventing Infections
• Nervous system infections are rare because its
tissues are well protected.
• Meningitis (men in JY tis) causes inflammation of the
membranes surrounding the brain and spinal cord.
• The most serious form of meningitis can be
prevented with a vaccine.
• A bite from an infected animal can transmit rabies,
an infection of the central nervous system.
• Avoid contact with animals that act sick or behave
strangely.
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Section 11.3 Your Nervous System
Living with Epilepsy
• Sudden, uncontrolled nerve impulses in the brain
can lead to a seizure.
• People with a disorder called epilepsy are prone to
seizures.
• Epileptic seizures include facial twitching, loss of
awareness, and muscle spasms.
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Section 11.3 Your Nervous System
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Section 11.3 Your Nervous System
Preventing Headaches
• The most common problem of the nervous system
that people experience are headaches.
• Proper diet, exercise, and sleep can help prevent
headaches.
• If you can identify certain foods or odors that trigger
headaches, you may be able to avoid those triggers.
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Section 11.3 Your Nervous System
Vocabulary
neuron
cerebrum
The basic unit of the nervous system that
carries nerve impulses.
A part of the brain that contains several
specialized regions that receive messages from
sense organs, and control movement, memory,
communication, and reasoning.
cerebellum
A part of the brain that coordinates movements
and balance.
brain stem
The area of the brain between the cerebellum and
the spinal cord; it controls automatic functions such
as heartbeat and blood pressure.
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Section 11.3 Your Nervous System
Vocabulary
spinal cord
reflex
A thick column of nerve tissue in the central
nervous system that links the brain to most of
the nerves in the peripheral nervous system.
An automatic response of the nervous system to
the environment.
concussion
A bruiselike injury to the brain caused by brain
tissue hitting the skull during a collision.
coma
A prolonged period of deep unconsciousness.
paralysis
The loss of the ability to move and feel some
part of the body.
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Section 11.3 Your Nervous System
Vocabulary
meningitis
seizure
epilepsy
An infection that causes inflammation of the
membranes surrounding the brain and spinal
cord.
An episode of erratic nerve impulses in the brain
that may lead to loss of consciousness, muscle
spasms, and other uncontrollable symptoms.
A condition in which a person is prone to
seizures.
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Section 11.3 Your Nervous System
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Section 11.3 Your Nervous System
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Section 11.3 Your Nervous System
End of Section 11.3
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