Download Dr. Melanie D. Osterhouse presents Action potentials and

Neuron
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4 regions:
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Cell body
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Presynaptic terminals
Dentrites
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Contains nucleus
Metabolic center
Receive incoming signals
from other nerve cells
Axon
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Transports signals away to
other neurons
What is an Action Potential?
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Defn. Electrical signal conveyed down an axon
What causes it?
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An environmental stimulus (ex. Light, pressure,
odor, mechanical contact, etc.)
These stimuli cause the axon hillock (start of
the axon) to create an action potential
The action potential continues to the end of the
axon
Action Potential Properties
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Travel small or large distances (.1mm-3m)
Rapid and transient (duration of about 1ms)
Constant amplitude (100mV)
All or none nerve impulse
Travels in one direction (principle of dynamic
polarization)
(Dominos display)
Action Potential Overview
environmental stimulus
Axon hillock
(initial segment)
resting membrane potential (-70mV)
threshold (-55mV)
Na+ influx thru open Na+ channel activation gates (+30mV)
depolarization
Repolarization K+ outflow thru open voltage-gated K+ channels
Na+ channel inactivation gates close
hyperpolarization
membrane more permeable to K+ than normal
K+ channel closes
returns to resting potential
adjacent membrane voltage gated Na+ channels open
depolarization propagated (aka conduction)
How does the action potential
impact the neuromuscular junction?
action potential
axon terminals
synaptic end bulbs
synaptic vesicles
binds to plasma membrane
ACh binds to receptors at the muscle moter endplate
located in mid-muscle
cation (Na+) channel opens changing the resting membrane potential
muscle action potential created
muscle contraction