The Nervous System
Medical Biology
Mission Hills High School
Functions of the Nervous
System
Sensory
 Integrative
 Motor

Divisions of the Nervous System

The nervous system is
divided into
- Central Nervous System
(CNS), containing the brain
and spinal cord
- The Peripheral Nervous
System (PNS), containing the
nerves and ganglia
The Peripheral Nervous System
contains…
cranial nerves
which arise from
the brain
 Spinal nerves
which arise from
the spinal cord as
well as many
branches

Nerve Tissue

The nerve tissue
is composed of
two types of cells:
-neurons, which
conduct impulses,
and…
-neuroglia which
support the
neurons
Neurons


Structural and functional units
of the nerve system
Perform sensory, integrative
and motor functions
-sensory: ability to sense
(receive) information
-Integrative: ability to process
the information received and
arrive at a desire to respond.
-Motor: ability to initiate a
response with body movement
or secretion of a product.
Lots of types of neurons
Structure of neurons
Each contain a cell body
with a nucleus
 Numerous dendrites:
receive and send
information to the cell
body
 A single axon: moves
impulse from dendrites
and body to dendrites or
body of other neurons.

5
3
1
2
4
1. Cell Body

Part of the neuron
that contains the
nucleus
2. Nucleus

The nucleus is the
control center of the
cell and contains the
genetic information in
the form of DNA
3. Dendrites

Dendrites carry
impulses (from
another cell’s axon
tips) toward the cell
body
4. Axon

The axon carries
impulses away from
the cell body.
5. Axon Tip(s)

The axon tips release
chemicals that enable
the impulse to cross
the synapse
Axon
Tips
6. Synapse

The space between
the axon tip and the
next dendrite. It is
also called the
synaptic cleft.
Label and tell the function of
each neuron part
Myelin in PNS and CNS



Axons in large
peripheral nerves
contain a fatty,
supportive sheath
called myelin sheath
Presence of myelin
makes nerve tissue
appear white (white
matter)
In CNS spinal cord,
unmyelinated nerve
tissue appear gray
(grey matter)
What makes up the brain, the spinal cord
or your peripheral nerves?







Neurons are “the cell”
Cell body
Nucleus
Axon
Dendrite
What do you think
surrounds the cell?
What other organelles
would be needed?
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
How are neurons connected?

Synapses!!
Why are neurons connected?
More neuron connections!
Close up look at your synapse (The Gray Matter)
AXON
What is this
in the
membrane?
The synapse where the action
happens
The next cell’s plasma
membrane
Transport
protein
How does the Synapse carry the
signal?
1.
2.
3.
4.
impulse travels down the axon (The White Matter)
Vesicles with neurotransmitters move toward the
membrane
Neurotransmitters are released and diffuse toward the
next cell’s plasma membrane
The chemicals open up the transport proteins and allow
the signal to pass to the next cell
The synapse carries a signal from cell to cell
1
2
3
4
There are lots of proteins and chemicals in
your body to do the work
Why is it important that it is an electrical current?
How many synapses
are in one neuron?
1,000 to 10,000!!
What do you think can change
neurons and their connections?

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Accidents
Drugs
Alcohol
Disease
Drugs and alcohol bind important receptors on neurons
Repeated binding causes the neuron to die
Drugs = neuron death
Alcohol damages dendrites - can
repair after abstinence
Alcohol blocks
receptors and slows
down transmission
100 Billion or so neurons - what’s the
problem with some of them dying?
•Cells multiply all the time
- will your neurons?
•Does everyone react the
same way to accidents, or
drugs and alcohol?
•Do all organisms react the
same to all stimulus?
•Which of your activities
use your neurons?
What if
neurons die
here?
or here
or here
or here
or here