The first event to occur when an adequate stimulus is applied to a neuron is:
A) the membrane potential moves immediately to a value of +30 mV.
B) the potassium channels open.
C) the sodium channels are inactivated.
D) some of the sodium channels at the point of stimulation open.

Question

Quizplus · Accepted Answer

When an adequate stimulus is applied to a neuron, some of the sodium channels at the point of stimulation open. This allows a rapid influx of sodium ions, which causes depolarization of the membrane potential. As a result, an action potential is initiated and propagated down the axon. Choice A is incorrect because the membrane potential does not immediately move to +30 mV; rather, it gradually depolarizes to a peak value of approximately +40 mV. Choice B is incorrect because potassium channels do not open until later in the action potential, during the repolarization phase. Choice C is incorrect because the sodium channels are activated, not inactivated, during the initial depolarization phase of the action potential.

The First Event to Occur When an Adequate Stimulus Is