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