Comparative Vertebrate Physiology Action potentials.

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Presentation transcript:

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