Repolarization of an axon during an action potential is...

Repolarization of an axon during an action potential is produced by
a. inward diffusion of $\mathrm{Na}^{+}$.
b. active extrusion of $\mathrm{K}^{+}$.
c. outward diffusion of $\mathrm{K}^{+}$.
d. inward active transport of $\mathrm{Na}^{+}$.

Key Concepts

Action Potential

An action potential is a rapid, temporary change in the electrical membrane potential of a cell, primarily found in neurons and muscle cells. It involves a sequence of events where the membrane potential sharply rises (depolarization) and then falls (repolarization), which allows the transmission of electrical signals along the cell. This process is fundamental to nervous system function and communication between cells.

Repolarization

Repolarization is the phase of the action potential in which the membrane potential returns to its resting negative value after depolarization. This phase is marked by the closing of voltage-gated sodium channels and the opening of potassium channels, leading to the efflux of positive potassium ions out of the cell, thereby restoring the negative internal environment.

Potassium Ion Diffusion

Potassium ion diffusion refers to the passive movement of potassium ions down their concentration gradient out of the cell during repolarization. This movement is crucial in reducing the positive charge inside the cell after the initial depolarization caused by sodium influx, helping to restore the resting membrane potential.

Voltage-Gated Ion Channels

Voltage-gated ion channels are specialized proteins in the cell membrane that open or close in response to changes in membrane potential. They play a critical role in generating and propagating action potentials by regulating the flow of ions such as sodium and potassium, with specific channels activating at different phases of the action potential.

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