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HOW THE NERVOUS SYSTEM
FUNCTIONS!
SIMPLE EDITION
By Brad Zeller
The Nervous System
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The nervous system is one of many systems used
within our bodies
This system is one of the most intricately organized
aggregate of matter on the face of this planet
Its unique ability to send and receive specific signals
from specific parts of the body using nerve cells,
chemicals, and electrical impulses is simply amazing
Different Pathways
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Afferent nerves – (sensory nerves) are nerves that
carry information about the external environment to the
brain and spinal cord
Efferent nerves – (motor nerves) are the nerves which
do the opposite and carry information out of the brain
and spinal cords to regions of the body where work can
be done
Most of the information will move through and be
processed by neural networks, which integrate sensory
input and motor output
The Main Divisions
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The central nervous system (CNS) is made up of the
brain and spinal cord
More than 99% of all nerves
cells in our body are located
here

The peripheral nervous
system (PNS) is the network
of nerves which connects the
brain and spinal cord to the
rest of the body
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Subdivisions of the PNS
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1) The somatic nervous system
consist of the sensory nerves, whose
function is to convey information
from the skin and muscles to the
CNS that report pain or
temperature, and also contains
motor nerves, which tell muscles
what to do
2) The autonomic nervous system
takes messages to and from the
body’s internal organs (processes
like breathing, heart rate, and
digestion)
Subdivisions of the Autonomic Nervous System
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1) The sympathetic nervous system is the system
that arouses the body to mobilize it for action
 System
that gives you the “fight or flight” reaction
 Also involved in stress
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2) The parasympathetic nervous system calms the
body
The Cellular Level
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In each system a lot of work is being done at a
much smaller scale where the nerve cells, chemicals,
and electrical impulses work together to send
messages at a rate of 330 miles per hour
 Because
of these speeds,
information can travel from the
brain to your hands (or vice
versa) within a matter of
milliseconds!
The Two Main Types of Cells Associated
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Neurons – nerve cells from the nervous system that
handle the information processing function
The typical human brain contains above 100 BILLION
neurons!
 ALSO, the average neuron is a complex structure with as
many as 10,000 physical connections with other cells!
 This explains how a message can be sent so friggin fast!

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Glial cells – cells in the nervous system that provide
support, nutrients, and other functions and keep neurons
running smoothly
Specialized Cell Structure!
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As every cell does a neuron has a cell body. The cell
body contains the nucleus, which directs the
manufacture of substances that the neuron needs for
growth and maintenance.
There are also dendrites. Dendrites are treelike
fibers that project from a neuron. They will receive
information and direct it toward the nucleus of the
cell.
 Having
numerous dendrites helps increase the surface
area so when a signal is sent out, more neurons will be
able to receive it.
Specialized Cell Structure!
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Another portion called the axon carries information
away from the neuron to other neurons
 Axons
are extremely thin, but can run extreme distances
as well. In fact, some axons extend 3 feet in length!
 Encasing and insulating most axons is a myelin sheath,
which consist of a layer of cells containing fat.
Specialized Cell Structure!
Cell Body
Dendrites
Vesicle
Nucleus
Myelin Sheath
around Axon
Synapses
Axon
Terminal
Button
Axon Terminals
Different Cell
The Neural Impulse
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The way these neurons send information from one to
another is through brief electrical impulses
Each neuron will send the impulse to the next
through the axon electrically because the membrane
of an axon is very unique
Each axon has thousands of tiny gates that can
open making the membrane semi permeable
These gates are known as ion channels
The Neural Impulse
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The ion channels will open and close allowing ions to
pass in and out of the cell
When a cell is resting (not transmitting information) the
ion channels are closed creating a slight negative
charge. Outside the cell, the charge is positive making
the resting neuron become what is known as polarized.
The resting potential (the stable, negative charge of an
inactive neuron) has a potential between -60 and -75
millivolts, meaning each cell maintains the potential for
about 75,000 volts of electricity!
The Neural Impulse
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So because opposite charges attract the ions inside and
outside the cell will rush to each other when given the
chance
So when the impulses run down the neuron by opening
and closing ion channels, this allows the ions to flow in
and out
As certain ions move in and out of the neuron, the
neuron becomes positively charged making it
depolarized. Once negative ions rush back in the neuron
will return to a negative charge.
Then the same process occurs as the next group of
channels flips open briefly
Synaptic Transmission
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As the impulse goes all the way
down the axon, it will eventually
reach what is known as a
synapses. These are small gaps
between neurons, which are
referred to as synaptic gaps.
Before an impulse can cross a
synaptic gap, it must be converted
into a chemical signal
Each axon branches out into
numerous fibers that end in a
structure called terminal buttons
Within each terminal button are
chemical substances known as
neurotransmitters
Synaptic Transmission
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Neurotransmitters will carry the information across
the synaptic gap to the next neuron to continue the
transmission of the message
The neurotransmitters will flood the synaptic gap
when the impulse reaches them. Their movement is
random allowing some of them to bump into
receptor sites of the next neuron (they can be
interpreted as a lock and key).
There are several neurotransmitters in our body and
all have major effects on behavior
Common Neurotransmitters
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Acetylcholine – involved in action of muscles, learning, and
memory
GABA – keeps neurons from firing
Norepinephrine – stress stimulates the release of
norepinephrine
Dopamine – helps to control voluntary movement and
affects sleep, mood, attention, learning, and reward
recognition
Serotonin – involved in regulation of sleep, mood, attention,
and learning
Endorphins – shields the body from pain and elevates
feelings of pleasure
Oxytocin – plays an important role in the experience of
love and social bonding
In Conclusion…
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…all of these mechanisms work together within our
nervous system so that we are able to live our lives
happily.
They help to keep us safe and sense danger, and at the
same time allows us to feel the special feeling of love.
The nervous system is just another magnificent portion
of our body that all of us need in order to live our long,
happy lives!
Works Cited
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Pictures
 http://pdginnovates.wordpress.com/2010/05/11/the-
science-of-simulation-mirror-neurons/
 http://www.democraticunderground.com/discuss/dubo
ard.php?az=view_all&address=222x51167
 http://www.tutorbene.com/index.aspx?PageID=85
 A bunch of clip arts from Microsoft Powerpoint
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Information
 All
from the book: Experience Psychology by Laura A.
King. (all info was between pages 40-49)