“Stationary” Fluctuations of Na Current in Myelinated Nerve
Current in Na channels of nerve or muscle is transient. Its activation upon a depolarizing stimulus is followed by a spontaneous inactivation. Study of Na current fluctuations with methods that require stationarity is nevertheless possible: inactivation tends to be incomplete, so that a measurable Na current persists over hundreds of milliseconds, long enough for recordings in a nearly stationary state. While this sustained current is small and unimportant for the propagation of the nervous impulse, it allows us to analyze gating at just those membrane voltages where the Na channels are most sensitive to the electric field.
KeywordsSodium Channel Open Probability Slow Inactivation Current Fluctuation Myelinated Nerve Fibre
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