In the formation of an action potential, the neuronal membrane first exhibits a

Question

In the formation of an action potential, the neuronal membrane first exhibits a resting potential in which only the [_____] are open and the membrane voltage is approximately -70 mV. In the depolarization phase, the membrane depolarizes beyond the threshold value, opening the [_____] sodium gates, leading to an influx of Na+. The increased Na+ permeability causes the membrane voltage to temporarily reverse itself, reaching a value of approximately +40 mV. It is this reversal of membrane potential that constitutes the [_____]. In the depolarization phase, the sodium gates are [_____] and the potassium gates open, allowing potassium ions to diffuse across the membrane and establish a negative potential at that location. Almost as soon as they open, the potassium gates close, leaving the potassium leak channels as the primary path of ion movement across the membrane and re-establishing the [_____].

(1) K+ leak channels; voltage-regulated; action potential; inactivated; resting potential

(2) active K+ channels; closed; resting potential; closed; membrane potential

(3) inactivated K+ channels; uninhibited; nerve impulse; closed and inactivated; original state

(4) passive K+ channels; activated; membrane depolarization; inhibited; action potential

(5) passive Na+ channels; voltage-regulated; membrane potential; activated; original potential

Explanation / Answer

(1) K+ leak channels; voltage-regulated; action potential; inactivated; resting potential

In the formation of an action potential, the neuronal membrane first exhibits a resting potential in which only the [_K+ leak channels____] are open and the membrane voltage is approximately -70 mV. In the depolarization phase, the membrane depolarizes beyond the threshold value, opening the [__voltage-regulated___] sodium gates, leading to an influx of Na+. The increased Na+ permeability causes the membrane voltage to temporarily reverse itself, reaching a value of approximately +40 mV. It is this reversal of membrane potential that constitutes the [_action potential___]. In the depolarization phase, the sodium gates are [__inactivated___] and the potassium gates open, allowing potassium ions to diffuse across the membrane and establish a negative potential at that location. Almost as soon as they open, the potassium gates close, leaving the potassium leak channels as the primary path of ion movement across the membrane and re-establishing the [__resting potential___].

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