The Nervous
System
The human nervous system….
1.
2.
3.
4.
Receives
Processes
Stores
Transmits
- stimulus from inter/exter. environ.
- message sent
- brain remembers stimulus
- brain sends reactive message
….information that comes from the various
parts of the body (internal) and the external
world.
The Nervous System has 2 main parts
The Peripheral
Nervous System
(PNS)
_________________
The Central Nervous
System (CNS)
________________
Which is made up of:
Which is made up of
Sensory Motor
Nerves
(All over your body)
The Brain and
The Spinal Cord
What is the Nervous System made of?
Neurons! (Nerve Cells)
– All of the organs and nerves of the nervous system
are made of approximately 100 billion Neurons.
 Neurons are special cells that can
send, receive and transmit electrical
Messages called nerve impulses
 Each neuron is made of:
–
–
–
–
Dendrites
A Cell Body
An Axon
Axon Terminals
Neurons
Real Neuron Images
Anatomy of a Neuron

Dendrites:
these are “branched” processes
are specialized to receive input
and carry information toward
the cell body.

The Cell Body:
- is the metabolic center of the
neuron (where energy is made).
- contains the nucleus (center) of the cell
- most proteins needed for functioning are made
here
- incoming signals from dendrites meet here.
Anatomy of a Neuron

Axon:
•
is larger in diameter than dendrites.
is specialized to carry information away from
the cell body.
may be very long, up to 1 meter!

Axon Terminals
•
•
•
•
the end of the axon.
Sends the signal on to other
neurons.
Draw your own picture of a neuron
here and label the 4 parts
Characteristics of Neurons
1) Neurons can be stimulated: they react to
chemical signals by transforming them
into electrical signals.
2) Neurons are conductive: they transmit
nerve impulses to other cells.
3) Neurons are needy: they require great
amounts of glucose and oxygen to
function (20% of body’s energy goes to
cells. Neurons will die within minutes
without oxygen).
Neurotransmission
How do neurons communicate?
•
•
Neurons interact with other neurons through
synapses.
The axon terminals of one neuron will end near
(but do not touch) the dendrites of another neuron.
• Presynaptic neuron: sends out information
• Postsynaptic neuron: receives information

Note: There is no physical connection
between the two neurons!
Synapse and Neurotransmitter Intro Video
Nerve Impulses
When a neuron registers an
internal stimulus (from
another neuron or a
hormone) or an external
stimulus (such as a sound,
touch, heat, electrical
shock, pain, odour) it will
produce an electric current
known as a nerve impulse
or an action potential (AP).
The nerve impulse travels
down the axon to the
axon terminals at speeds up
to 430 km/h.
Delay reaction Ruler Test: Delay from sight to brain to finger muscles.
Fill in the blanks with the following
words:
Relayed, Received, Transmitted, or
Processed,
Nerve impulses are:
1)
2)
3)
4)
___Received ___by the dendrites;
__Processed____ by the cell body;
__Transmitted__ through the axon;
___Relayed___ by the axon terminals.
Review Questions
1) What is the main function of the nervous
system?
2) What are the 2 main parts of the nervous
system and how do they differ?
3) What is the nervous system made up of?
4) What are the 4 main parts of the neuron
and what are their specialized functions?
5) What is a synapse?
6) Draw a picture of a synapse including pre
and postsynaptic neurons. Make sure to
label all structures in your diagram.
7) What are two names for the electric
current that travels down a neuron?
8) What is the name of the chemical
messengers found at inside the axon
terminal?
9) What part of the neuron receives the
nerve impulse?
Question Answers
Answers to HW Review Questions
1) What is the main function of the nervous
system?
The nervous system receives, processes,
stores and transmits information that comes
from parts of the body and the external
world.
2) What are the 2 main parts of the nervous
system and how do they differ?
The central nervous system is composed of
the brain and the spinal cord.
The peripheral nervous system is composed of
the nerves (motor and sensory) all over your
body.
3) What is the nervous system made up of?
The nervous system is composed of more than a
billion nerve cells or neurons.
4) What are the 4 main parts of the neuron and
what are their specialized functions?
Dendrites: receive inputs from other neurons
and carry messages to towards the cell
body.
Cell Body: Makes energy and proteins for the
neuron, processes the inputs from the
dendrites.
Axon: transmits the nerve impulse away from
the cell body.
Axon Terminals: relays (passes on) the nerve
impulse to another neuron.
5) What is a synapse?
The connection between 2 neurons rough which they
interact.
6) Draw a picture of a synapse including pre and
postsynaptic neurons. Make sure to label all
structures in your diagram.
7) What are two names for the electric current
that travels down a neuron?
-Nerve impulse, action potential (AP)
8) What is the name of the chemical
messengers found at inside the axon terminal?
-Neurotransmitters
9) What part of the neuron receives the nerve
impulse?
- the dendrite
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