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Essential Question: What are the major
functions of the central nervous system?
Basic Idea
• The nervous system contains billions of cells called
neurons. Neurons communicate with one another
through the central and peripheral nervous
systems.
Basic Vocab
Central Nervous System-brain and spinal cord
Peripheral Nervous System-nerve cells that send
messages between the central nervous system and
other parts of the body
2
Neurons-nerve cells that run through our entire
bodies and communicate with each other
Neurons
The nervous system has two parts. The central nervous system consists of
the brain and spinal cord. The peripheral nervous system is made up of
nerve cells that send messages between the central nervous system and
other parts of the body. Nerve cells are called neurons.
Components of a Neuron
Components of a Neuron (con’t)
• The cell body produces energy
that fuels the neuron’s activity.
• Dendrites receive information
from other neurons and pass the
message through the cell body.
• An axon transmits information
away from the cell body.
• Myelin is a white, fatty substance
that covers the axon, insulating
and protecting it. The myelin
sheath helps to speed up the
work of neurons.
• Axon terminals branch out at the
end of the axon.
Essential Question: What are the major
functions of the central nervous system?
The Communication Process
• Messages are sent from the axon terminals of one neuron to
the dendrites of other neurons
• In order for this process to happen, the message must cross
a synapse.
• A synapse is a junction between the axon terminals of one
neuron and the dendrites of another.
• Messages travel in only one direction. Messages:
– enter the dendrites
– travel through the cell body and axon to the axon
terminals
– cross the synapses to the dendrites of other neurons
Neural Transmission
Domino Metaphor
The process involved in the transmission of
messages between neurons is similar to the
chain reaction of a row of falling dominoes.
Neurons, like the dominoes, transmit messages
in only one direction
Neurons always transmit messages at the same
strength—just as the dominoes do not gain
speed as they fall down.
Visual of Neural Transmission
The Synapse
Locate the synapse in the big picture on pg 67
The synapse is a small gap-less than a millionth of
an inch wide-and is filled with fluid that transmits
the chemicals from one neuron to another.
Locate the synapse in the smaller picture on pg 67
The neurotransmitters travel from the axon
terminals, across the synapse, to the dendrites of
the receiving neuron.
Animated visual of the synapse with a neuron
firing (release neurotransmitters)
Neurotransmitters…
Neurons send messages across synapses through
the release of neurotransmitters.
Are chemicals that are stored in sacs in the axon
terminals
Are a way to communicate messages: a neuron fires
by releasing neurotransmitters
There are several types
Have different functions
Are involved in everything you do
Can cause diseases or psychological disorders if you
have too many or too few neurotransmitters
Neurotransmitters-Application
Endorphins are neurotransmitters that naturally reduce pain
and boost mood.
Flooding the brain with painkillers, antidepressants, or other
drugs may cause the brain to stop producing endorphins.
When such drug(s) is discontinued, a person may experience
a period of discomfort—ranging from mild to agonizing—
until the brain resumes production of endorphins.
What are other possible ramifications of taking
antidepressants or painkillers?
Do you believe the benefits outweigh the potential harm?
Neurotransmitters:
Norepinephrine and Serotonin
People who have too much or too little of norepinephrine
and/or serotonin often suffer from depression.
Doctors may prescribe antidepressant drugs to regulate these
neurotransmitters in their patients’ bodies.
Although sales of these drugs total in the billions of dollars,
their total effect is variable and their side effects can cause
additional issues.
Cost vs. Benefit
Is it a possibility to treat depression through psychological
therapy as an alternative to drug therapy?
(You’ll learn more about depression in Chapter 18 & 19)
The Central Nervous System Visualpage 69
The central nervous systems consists of the neurons of
the spinal cord and the brain.
The brain is the most complex part of the nervous system
The spinal cord is a column of nerves about as thick as a
thumb that extends from the brain down the back.
The spinal cord transmits messages between the brain
and the muscles and glands in the body.
The spinal cord sends messages to specific muscles.
The spinal cord is involved in spinal reflexes.
Damage to the Spinal Cord: Paralysis
Paraplegia
Paralysis of the legs
Usually from damage to the spinal cord below the
neck
Quadriplegia
Paralysis of the arms and legs
Usually from damage in the neck region
The Peripheral Nervous System
Responsible for transmitting messages between the central
nervous system and all parts of the body
Is made up of the somatic nervous system and autonomic
nervous system
The Somatic Nervous System
The Autonomic Nervous System
• The somatic nervous system
transmits sensory messages to the
central nervous system.
• It carries messages from the
voluntary muscles and sense organs.
• It is activated by touch, pain, changes
in temperature, and changes in body
position.
• The autonomic nervous system regulates
the body’s vital functions, such as
heartbeat, breathing, digestion, and
blood pressure.
• It has two divisions.
• The sympathetic nervous system reacts to
stress.
• The parasympathetic nervous system
restores peace to the body’s systems
Essential Question: What are the major
functions of the central nervous system?
FUNCTIONS OF THE PERIPHERAL NERVOUS SYSTEM
The autonomic nervous system has two parts:
The Sympathetic nervous system
Reacts to Stress
Fight or flight-prepares the body for making the decision to fight or run away
Digestion suppressed, heart & respiration rates increase, elevates blood
pressure
The Parasympathetic nervous system
Restores Peace
Rest and digest-restores the body’s reserves of energy after intense activity
Heart rate, blood pressure, & digestion return to normal, breathing slows down