What happens to the neuron during the relative refractory period?

During the relative refractory period, the neuron can fire again, but only with a stronger-than-normal stimulus. This phase occurs right after the absolute refractory period, when the neuron has just completed an action potential and is in the process of returning to its resting state. During this time, not all of the sodium channels have returned to their resting state, and the neuron is still hyperpolarized due to the continued outward movement of potassium ions.

Because of this hyperpolarization, a stimulus that might normally be sufficient to trigger an action potential is not enough. However, if the stimulus is strong enough, it can overcome the altered threshold of excitability and result in another action potential. This characteristic is crucial in ensuring that action potentials are distinct events and that there’s a controlled sequence of activation and recovery in neuronal signaling.

This understanding underscores why the other options are not accurate representations of the relative refractory period. The neuron is not completely unresponsive (which would occur in the absolute refractory period), nor is it in the process of depolarization in the way implied, and it is not merely completing action potentials without the possibility of new firing. The focus on the requirement for a stronger stimulus is key to understanding this specific phase of neuronal activity.