velocity summary Jan21

velocity summary Jan21 - recall the copper wire analogy....

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conduction velocity – summary Jan 21, 2012 how fast can spikes travel? (i.e., how fast is conduction velocity )? 6-100 mph (6 in optic nerve, 100 in skeletal muscle proprioreceptors) why isn’t this faster? because the charge that enters at point “A” can not depolarize the entire length of axon -- imagine a small number of charges and a very long axon. what determines conduction velocity? charge spreads quickly. therefore, the question is whether the charge that enters at segment “A” can depolarize a long or short segment of axon (at point “B”). what determines the length of this axon segment? diameter
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Unformatted text preview: recall the copper wire analogy. leak will positive charge leak out of the axon before it moves from point A to B, B to C, etc.? capacitance e.g., the amount of charge needed to depolarize segment B to spike threshold. if the capacitance is low then only a small amount of charge is needed to depolarize segment B, and residual charge can spread to (& depolarize) segment C. .. conduction will be fast if the capacitance is high then a large amount of charge is needed to depolarize segment B, and this leaves little or no residual charge to depolarize segment C conduction will be slow...
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This note was uploaded on 04/05/2012 for the course NPB NPB 101 taught by Professor Weidner/wingfield during the Spring '08 term at UC Davis.

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