Nervous System: Part I
The Nervous System
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Your body’s communication’s network &
control center
Peripheral Nervous System (PNS)-gathers info
from inside & outside the body
Central Nervous System (CNS)-receives this
info & initiates a response-composed of the
brain & spinal cord
Messengers & receivers of these
transmissions are NEURONS (nerve cell)
Three Types of Neurons
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Sensory-carry from
sense receptors to
CNS (5 senses)
Motor-carry signals
from CNS to muscles
or glands
Interneurons-carry
electrical
connections within
the CNS
Functions of Neurons
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Cell body-contains nucleus & cell membrane
Dendrites-branching projections of the cell
body, carry impulses into the cell.
Axon-Threadlike extension carries impulses to
& from the cell, at the end of axon is the
axon terminal
Myelin Sheath-Insulates the axon & speeds
up transmission of the impulses
Synapse-point of contact at which impulses
are passed from one cell to another
Electrical impulse
The Nerve Impulse
Let’s draw neurons!
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Look at the drawing on page
517 of your health book.
You will need 4 different colors
markers/pencils, for the:
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cell body
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dendrites
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axon/terminal
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synapse
Draw your neuron on a piece of
paper
color and label the parts
Right Brain--- Left Brain
Sitting at your desk, lift your right foot off
the floor and make clockwise circles
Now, while doing this, draw the number
"6" in the air with your right hand.
[Your foot will likely change direction,
and there's nothing you can actually do
about it.]
Reflex Action (Unconscious)
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If the safety of our body
requires a very quick
response, the signals may
pass directly to a motor
neuron for instant,
unthinking action. This is
a reflex action. Signals
sent via the spinal cord
List as many examples of
a reflex action as you can:
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http://www.bbc.co.u
k/schools/gcsebitesi
ze/biology/humansa
sorganisms/4nervou
ssystemrev4.shtml
Part II: Nervous System
Voluntary Actions (Conscious
Act)
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Impulses passed via the
brain
What is the chain of
events that happens from
the instant you hear the
phone ring until you pick
up the phone?
Every time a stimulus—
such as a ringing
telephone—is detected,
the body's three kinds of
neurons send a nerve
impulse through the
nervous system.
Nerve Impulse Activity
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In groups put the following path of
a nerve impulse in the correct
order:
1.The nerve impulses pass to
interneurons in the brain.
2.Receptors in your ear pick the
sound of a ringing phone
3.Muscles in the arm carry out the
response and you reach to pick up
the phone
4. Impulses travel along motor
neurons to the muscles
5. Receptors trigger nerve impulses
in sensory neurons
6. Your brain interprets the impulses
from many interneurons and you
realize the phone is ringing. Your
brain also decides that you should
answer the phone.
Correct order…
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2. Receptors in your ear pick the sound of a ringing
phone
5. Receptors trigger nerve impulses in sensory
neurons
1. The nerve impulses pass to interneurons in the
brain.
6. Your brain interprets the impulses from many
interneurons and you realize the phone is ringing.
Your brain also decides that you should answer the
phone.
4. Impulses travel along motor neurons to the
muscles
3. Muscles in the arm carry out the response and you
reach to pick up the phone
The Brain
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Largest, most complex part of the
nervous system
Weighs 3 pounds, contains billions of
neurons
Without oxygen it can only last 4-5
minutes
Cerebrum
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Forms our intellect & personality
Divided into two hemispheres
Left-language & logic
Right-imagination & emotional
responses
Does not fully develop until late teens
or early-mid 20s!!!
Phineas Gage
If an explosion sent a steel rod
through your head, would you
be able to get up? Would you
be able to walk and talk? Could
you tell your doctor what
happened to you? Amazingly,
Phineas Gage did! But, could he
make a complete recovery with
a big hunk of his brain missing?