Which of the following statements about the phases of a neuronal action potential is TRUE?
A) During the after-hyperpolarization phase, the permeability of the membrane to sodium ions is greater than its permeability to potassium ions.
B) During the after-hyperpolarization phase, the permeability of the membrane to potassium ions is greater than its permeability at rest.
C) During the repolarizing phase, the permeability of the membrane to sodium ions is greater than its permeability to potassium ions.
D) Potassium channels inactivate during the depolarization phase.
E) Repolarizing to negative membrane potentials causes the sodium channels to inactivate.

Question

Quizplus · Accepted Answer

During the after-hyperpolarization phase, the membrane potential becomes more negative than at rest due to a high permeability to potassium ions, which causes an efflux of K+ out of the cell. The permeability to sodium ions is very low during this phase. Option A is incorrect because during the after-hyperpolarization phase, the permeability to sodium ions is very low. Option C is incorrect because during the repolarizing phase, the permeability to potassium ions is greater than its permeability to sodium ions. Option D is incorrect because potassium channels do not inactivate during the depolarization phase but rather contribute to repolarization. Option E is incorrect because it is the inactivation of sodium channels that contributes to repolarization by preventing further influx of Na+ ions.

Which of the Following Statements About the Phases of a Neuronal