What is the characteristic of the period occurring at the end of phase 3 in the non-pacemaker action potential?

At the end of phase 3 in a non-pacemaker action potential, the characteristic identified is the relative refractory period. This phase occurs after the action potential has peaked and repolarization is underway, where the membrane potential is returning toward its resting state. During this time, the cell is still able to propagate another action potential, but a stronger-than-normal stimulus is necessary to initiate it.

The key aspect of the relative refractory period is that some sodium channels are still inactivated while others recover from inactivation, making it possible for a greater stimulus to cause depolarization again. This feature is critical for understanding how action potentials work and how excitability varies with time following an action potential.

The effective refractory period, conversely, refers to a time when no new action potential can be initiated, regardless of stimulus strength. This period corresponds with the earlier phases of repolarization. Resting membrane potential describes the state of the cell during non-activity, which is not a characteristic of the end of phase 3. The term "action refractory period" is not commonly used in standard electrophysiological literature; hence, it does not accurately describe the situation being asked about. Thus, the relative refractory period is the appropriate answer in the context of