What ions are responsible for depolarization and repolarization, respectively?

The correct answer identifies sodium (Na) ions as essential for depolarization and potassium (K) ions for repolarization in the context of action potentials in neurons.

During depolarization, when a neuron is stimulated, the permeability of the cell membrane changes, allowing sodium channels to open. As sodium ions rush into the cell, they create a positive charge within the neuron, leading to depolarization. This influx of sodium alters the membrane potential, moving it from a negative value toward zero and then into the positive range.

Following the depolarization phase, repolarization occurs, primarily through the outflow of potassium ions. After the peak of the action potential, potassium channels open, allowing potassium to exit the neuron. This efflux of positively charged potassium ions helps restore the negative membrane potential, effectively repolarizing the cell and returning it to its resting state.

Understanding this sequence of ion movements is crucial as it underlies the mechanism of electrical signaling in neurons, making it central to neural communication and function.