You arrive at class late, and walk in during the part of the lecture describing how action potentials work. The professor says, "the channels that allow sodium to flow into the neuron have just closed and the channels that allow potassium to flow out have opened." You can conclude that the cell is

Question

Quizplus · Accepted Answer

This description matches the repolarization phase of an action potential, where sodium channels close and potassium channels open to allow potassium to flow out, returning the neuron to its resting state.  When the inside of the neuron becomes positive because sodium has rushed into it, the neuron is depolarized. The channels that allow sodium in then close and the channels that allow potassium to flow out open. The outflow of potassium allows the cell to return to a resting state. This progression happens successively down the axon until all of the axon has depolarized and then been returned to the resting state.

You Arrive at Class Late, and Walk in During the Part