Which sequence best describes the events that initiate and terminate an action potential in a neuron?

• A. Resting potential (~ -70 mV); depolarization to threshold triggers rapid Na+ influx; Na+ channels inactivate and K+ channels open; repolarization with K+ efflux; membrane hyperpolarizes briefly before the Na+/K+ pump and channels restore the resting potential.
• B. Depolarization to threshold occurs via outward K+ movement followed by plateau, then return to baseline without hyperpolarization.
• C. Depolarization only occurs after hyperpolarization; Ca2+ influx drives the process with no Na+ involvement.
• D. Resting potential gradually increases toward zero without any ionic changes.

Answer: (A)