comparative vertebrate physiology action potentials
TRANSCRIPT
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Comparative Vertebrate Physiology
Action potentials
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Neuron anatomy and signaling
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Action potential
DepolarizationRepolarizationHyperpolarization
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Action potential Phases
Resting membrane potential Depolarization Repolarization Hyperpolarization
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Nernst equation Measures equilibrium potential Depends on:
absolute temperature valence ratio of concentration gradients
Ex =RTzF
In[X]I[X]II
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Nernst equation
If [K]o = 0.01M and [K]I = 0.1M
Ex =0.058z
log[X]I[X]II
Ex =0.0581
log0.010.1
=−58mV
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Action potential Hodgkin and Huxley theory
Resting membrane potential
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Action potential Resting membrane potential
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Action potential Hodgkin and Huxley theory
Depolarization: rising phase Na+ (5,000x)
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Action potential Hodgkin and Huxley theory
Repolarization : falling phase K+ (10x)
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Action potential Hodgkin and Huxley theory
Hyperpolarization
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Membrane permeability
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Protein gates Types
Chemical Occur between neurons
Voltage Occur within neurons
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Voltage gates
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Refractory period Absolute
Na+ activation gate open
Relative Na+ activation gate closed
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Channel toxins TTX (tetradotoxin)
Japanese puffer fish decreases Na+conductance increases K+conductance
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Channel toxins TEA (tetraethylammonium)
Synthetic organic compound increases Na+conductance decreases K+conductance
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Channel toxins
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Threshold An all-or-none event
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Threshold
Factors effecting Magnitude Duration
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Excitation curve
Volts
Milliseconds
1
1
2
2
3
3
4
4 5X
Chronaxie
A
B
C
Rheobase
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Impulse conduction
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Impulse conduction
Schwann cell secrete myelin
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Conduction velocity
Mylenated: 15 - 40 msec-1
Unmylenated: 0.4 - 0.5 msec-1