Transcript Comparative Vertebrate Physiology

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