Comparative Vertebrate Physiology

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Comparative Vertebrate Physiology

• Action potentials

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Neuron anatomy and signaling
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Action potential
Depolarization Repolarization Hyperpolarization
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Action potential

• Phases
• Resting membrane potential
• Depolarization
• Repolarization
• Hyperpolarization

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Nernst equation

• Measures equilibrium potential
• Depends on
• absolute temperature
• valence
• ratio of concentration gradients

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Nernst equation

• If Ko 0.01M and KI 0.1M

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Action potential

• Hodgkin and Huxley theory
• Resting membrane potential

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Action potential

• Resting membrane potential

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Action potential

• Hodgkin and Huxley theory
• Depolarization rising phase Na (5,000x)

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Action potential

• Hodgkin and Huxley theory
• Repolarization falling phase K (10x)

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Action potential

• Hodgkin and Huxley theory
• Hyperpolarization

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Membrane permeability
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Protein gates

• Types
• Chemical
• Occur between neurons

• Voltage
• Occur within neurons

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Voltage gates
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Refractory period

• Absolute
• Na activation gate open

• Relative
• Na activation gate closed

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Channel toxins

• TTX (tetradotoxin)
• Japanese puffer fish
• decreases Naconductance
• increases Kconductance

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Channel toxins

• TEA (tetraethylammonium)
• Synthetic organic compound
• increases Naconductance
• decreases Kconductance

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Channel toxins
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Threshold

• An all-or-none event

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Threshold

• Factors effecting
• Magnitude
• Duration

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Excitation curve
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Impulse conduction
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Impulse conduction

• Schwann cell secrete myelin

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Conduction velocity

• Mylenated 15 - 40 msec-1
• Unmylenated 0.4 - 0.5 msec-1