Ellipsoidal Insupportable Essay.docx

Ellipsoidal Insupportable Essay.docx - fibers are similar...

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fibers are similar, sensory fibers have significantly longer strength-duration time constants. As a result, sensory nerves have a longer strength-duration time constant and a lower rheobase than motor nerves.Many studies have suggested that differences in the expression of threshold channels could account for the sensory-motor differences in strength-duration time constant. The differences in strength-duration time constant and rheobase of normal sensory and motor axons are thought to reflect differences in expression of a persistent Na+ conductance. Additionally, sensory axons accommodate more to long-lasting hyperpolarizing currents than do motor axons, suggesting a greater expression of the hyperpolarization-activated inward rectifier channels. Finally, the electrogenic Na+/K+-ATPase is more active in sensory nerves, which have a greater dependence on this pump to maintain resting membrane potential than do motor nerves.Increases in the strength-duration time constant are observed when this conductance is activated by depolarization, or by hyperventilation. However, demyelination, which exposes internodal membrane with a higher membrane time constant than that of the original node, can also increase strength-duration time constant.The strength-duration time constant of
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  • Fall '17
  • Delois Cook

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