Transcript Regents Biology - Nick Williams` San Marin Science

Nervous System
Chapter 35
AP Biology
2010
Why do animals need a nervous system?
 Because the world
is always coming
at you!
Remember…
Poor
thinkbunny!
about
the bunny…
Regents Biology
2010
Nervous System
cerebrum
cerebellum
spinal cord
 Divided into:

Central nervous system
 brain & spinal chord

Peripheral nervous system
 nerves from senses
 nerves to muscles
cervical
nerves
thoracic
nerves
lumbar
nerves
femoral
nerve
sciatic
nerve
tibial
nerve
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2010
Nervous system cells
 Neuron
signal

direction
a nerve cell
dendrites
cell body
axon
signal direction
synapse
Regents Biology
2010
Fun facts about neurons
 Most specialized cell in
animals
 Longest cell

blue whale neuron
 10-30 meters

giraffe axon
 5 meters

human neuron
 1-2 meters
Nervous system allows for
1Regents
millisecond
Biologyresponse time
2010
Myelin coating
signal
direction
 Axon coated with insulation
made of myelin cells

speeds signal
 signal hops from node to node

330 mph vs. 11 mph
myelin coating
Multiple Sclerosis
 immune system (T cells) attacks myelin coating
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 loss of signal
2010
Transmission of a signal
 Think dominoes!

start the signal
 knock down line of dominoes by tipping 1st one
 trigger the signal

propagate the signal
 do dominoes move down the line?
 no, just a wave through them!

re-set the system
 before you can do it again,
have to set up dominoes again
 reset the axon
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Transmission of a nerve signal
 Neuron has similar system
protein channels are set up
 once first one is opened, the rest open
in succession

 all or nothing response
a “wave” action travels along neuron
 have to re-set channels so neuron can
react again

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How does a nerve impulse travel?
 Wave: nerve impulse travels down neuron

change in charge opens
the gates down the line
 “voltage-gated” channels
Gate
+
+ –
channel
closed

The rest
of the
dominoes
fall!
+
channel
open
“wave” moves down neuron = action potential
– – – + + + + + + + + + + + +
+ + + – – – – – – – – – – – –
Na+
+ + + – – – – – – – – – – – –
– – – + + + + + + + + + + + +
Regents Biologywave

How does a nerve impulse travel?
 Action potential
wave = nerve impulse, or action potential
 brain  finger tips in milliseconds!

In the
blink of
an eye!
K+
+ + + + + + + – – – – + + + +
– – – – – – – + + + + – – – –
Na+
– – – – – – – + + + + – – – –
+ + + + + + + – – – – + + + +
Regents Biologywave

Synapse
Junction between nerve cells


1st cell releases chemical to trigger
next cell
where drugs affect nervous system
synapse
Regents Biology
2010
Types of neurons
sensory neuron
(from senses)
interneuron
(brain & spinal chord)
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motor neuron
(to muscle)
2010