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The Nervous System
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The nervous system sends messages
through the nerves to coordinate all
the body’s activities.
neurons
cerebrum
cerebellum
brain stem
epilepsy
cerebral palsy
How the Nervous System Works
The nervous system coordinates all of the
activities in the body.
Your nervous system is a complex network that
allows communication between the brain and
parts of the body.
How the Nervous System Works
The brain, spinal cord, and nerves work together,
transmitting messages between organs, tissues,
and cells.
How the Nervous System Works
The central nervous system (CNS) consists of the
brain and spinal cord.
The peripheral nervous system (PNS) gathers
information from inside and outside your body.
How the Nervous System Works
The PNS includes nerves that extend from the
brain, spinal cord, and sensory receptors, such as
those in the skin.
The CNS receives messages from the nerves in
the PNS, interprets them, and sends out a
response.
Understanding Neurons
Neurons transmit messages from the brain
and spinal cord to the rest of the body.
Understanding Neurons
Neurons transmit messages to and from the spinal
cord and brain.
Neurons
Nerve cells
Understanding Neurons
The Three Types of Neurons
Sensory
Neurons
Carry messages from receptors in the body
to the CNS.
Motor
Neurons
Carry messages from the CNS back to
muscles or glands in response to an impulse.
Interneurons
Communicate with and connect other
neurons.
Understanding Neurons
The Three Main Parts of a Neuron
Cell Body
Dendrites
Axons
Understanding Neurons
The cell body of a neuron contains the nucleus,
which regulates the production of proteins within
the cell.
Understanding Neurons
Dendrites are branched structures that extend from
the cell body in most neurons.
Dendrites receive information and transmit
impulses toward the cell body.
Understanding Neurons
Axons transmit impulses away from the cell body
and toward another neuron, muscle cell, or gland.
Understanding Neurons
A nerve impulse begins when a sensory receptor is
stimulated. The impulse travels to the CNS and is
interpreted with the help of an interneuron.
Then an impulse is sent to a muscle cell or gland in
response to the stimulus.
The Central Nervous System
The central nervous system is made up of
the brain and spinal cord.
The brain and spinal cord send and receive
impulses to and from nerves in the body.
Sections of the Brain
The brain coordinates and controls the activities of
the nervous system.
Your brain helps you to receive and process
messages; to think, remember, reason, and feel
emotions; and to coordinate muscle movements.
Sections of the Brain
Three Main Divisions of the Brain
The
Cerebrum
The
Cerebellum
The
Brain Stem
The Cerebrum
Billions of neurons in the cerebrum are the center
of conscious thought, learning, and memory.
cerebrum
The largest and most
complex part of the brain
The Cerebrum
The cerebrum’s right and left sides, or
hemispheres, communicate with each other to
coordinate movement.
The right hemisphere controls the left side of the
body, and the left hemisphere controls the right
side of the body.
The Cerebrum
Left
Hemisphere
Right
Hemisphere
The center of
language,
reasoning, and
critical thinking
skills.
The center for
processing music
and art and
comprehending
spatial
relationships.
The Cerebrum
Each hemisphere of the brain has four lobes.
The Frontal
Lobe
Controls voluntary movements and has a role in use of
language. Possibly involved with intellect and personality.
The Parietal
Lobe
Involved with sensory information, including feelings of
heat, cold, pain, touch, and body position in space.
The Occipital
Lobe
Controls the sense of sight.
The Temporal
Lobe
Contains the sense of hearing and smell, as well as
memory, thought, and judgment.
The Cerebellum
The cerebellum coordinates the movement of
skeletal muscles and maintains the body’s posture
and balance.
Cerebellum
The second largest part of
the brain
The Brain Stem
Incoming sensory impulses and outgoing motor
impulses pass through the brain stem.
Brain stem
A 3-inch-long stalk of nerve cells
and fibers that connects the spinal
cord to the rest of the brain
The Brain
The Brain Stem
Parts of the Brain Stem
The medulla
oblongata
Regulates heartbeat, respiratory rate, and reflexes
such as coughing and sneezing.
The pons
Helps regulate breathing and controls the muscles
of the eyes and face.
The midbrain
Controls eyeball movement, pupil size, and the
reflexive response of turning your head.
The thalamus
Relays incoming sensory impulses from the eyes,
the ears, and from pressure receptors in the skin.
The
hypothalamus
Regulates body temperature, appetite, sleep, and
controls secretions from the pituitary gland.
The Peripheral Nervous System
The peripheral nervous system is made up of
the nerves that are not in the brain and spinal
cord.
The PNS carries messages between the CNS
and part of the body, signaling internal and
external changes.
The Peripheral Nervous System
The PNS is made up of:
the autonomic nervous system
the somatic nervous system
The Autonomic Nervous System
The autonomic nervous system controls such
involuntary functions as digestion and heart rate.
The Autonomic Nervous System
The autonomic nervous system consists of a
network of nerves divided into two smaller
networks:
the sympathetic nervous system
the parasympathetic nervous system
The Autonomic Nervous System
The sympathetic nervous system causes a reflex
when you are startled, sending messages that
cause your heart rate to increase.
Blood vessels in your muscles dilate, allowing
greater blood flow and preparing you to react in a
dangerous situation.
The Autonomic Nervous System
A reflex is the body’s spontaneous response to a
stimulus.
Reflexes can prevent injuries such as a burn from
a hot stove.
The Autonomic Nervous System
How Your Reflexes Work
The Autonomic Nervous System
The parasympathetic nervous system slows body
functions during periods of rest to conserve
energy.
It also stimulates production of saliva and stomach
secretions to promote the digestion of food.
The Somatic Nervous System
The somatic nervous system involves voluntary
responses that are under your control.
Sensory neurons relay messages from the eyes,
ears, nose, tongue, and skin to the CNS, and
motor neurons carry impulses from the CNS to
skeletal muscles.
Caring for Your Nervous System
Making healthful choices can protect your
nervous system from injury.
Making healthful choices keeps a nervous
system functioning properly.
Caring for Your Nervous System
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Eat a well-balanced diet
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Do not use drugs and alcohol, which can permanently
damage nerve cells.
Exercise regularly
Get enough sleep
Wear a safety belt when in a motor vehicle.
Never dive into shallow water
Wear a helmet and other protective gear while riding a
bicycle, motorcycle, or other open vehicle, or when
enjoying a contact sport.
Problems of the Nervous System
Headaches
Injury to the nervous
system affects the
immediate tissues, and
may lead to other
problems, including:
Head Injuries
Spinal Injuries
Meningitis
Problems of the Nervous System
Headaches can be caused by muscle tension,
eyestrain, exposure to fumes, a sinus infection,
dehydration, or food allergies.
Migraines are recurrent headaches that may be
accompanied by sensitivity to light.
Problems of the Nervous System
Each year, 435,000 American children and teens
sustain brain injuries.
Concussion
Contusion
Coma
a temporary loss
of consciousness
a bruising of the
brain tissues that
causes swelling
caused by major
trauma
Problems of the Nervous System
Spinal cord injuries require medical care.
Swelling of the spinal cord or the tissue around it
can result in temporary loss of nerve function. If the
spinal cord is severed, paralysis results.
Problems of the Nervous System
Meningitis is an inflammation of the spinal and
cranial meninges caused by bacterial or viral
infection.
Meningitis is very serious and can result in death.
Problems of the Nervous System
Degenerative nervous system diseases occur over
time as cells break down.
Multiple
Sclerosis
Parkinson’s
Disease
Alzheimer’s
Problems of the Nervous System
Causes of epilepsy include brain damage at birth,
infections, head injury, or exposure to toxins.
Epilepsy
A disorder of the nervous system that is
characterized by recurrent seizures—
sudden episodes of uncontrolled electrical
activity in the brain
Problems of the Nervous System
Physical therapy and medication help patients
cope with cerebral palsy.
Cerebral palsy
A group of neurological disorders that are
the result of damage to the brain before,
during, or just after birth or in early
childhood
After You Read
Reviewing Facts and Vocabulary
1. Where is the nucleus of a neuron
located?
The nucleus is located in the cell body.
After You Read
Reviewing Facts and Vocabulary
2. How can a reflex prevent injury?
A reflex is a spontaneous response of the
body to a stimulus. Reflexes allow a person
to respond to and avoid danger.
After You Read
Reviewing Facts and Vocabulary
3. What are some causes of nervous
diseases and disorders?
Some diseases of the nervous system are
degenerative, while others may result from
head injury or neurological problems.