Comparative vertebrate physiology
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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.

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Comparative Vertebrate Physiology

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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


Impulse conduction

  • Schwann cell secrete myelin


Conduction velocity

  • Mylenated: 15 - 40 msec-1

  • Unmylenated: 0.4 - 0.5 msec-1


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