Comparative Vertebrate Physiology Action potentials
Neuron anatomy and signaling
Action potential Depolarization Repolarization Hyperpolarization
Action potential Phases Resting membrane potential Depolarization Repolarization Hyperpolarization
Nernst equation Measures equilibrium potential Depends on: absolute temperature valence ratio of concentration gradients
Nernst equation If [K]o = 0.01M and [K]I = 0.1M
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
Impulse conduction
Schwann cell secrete myelin
Conduction velocity Mylenated: msec -1 Unmylenated: msec -1