What is the defining characteristic of a strong impulse during the relative refractory period?

A strong impulse during the relative refractory period can indeed trigger depolarization. The relative refractory period occurs after the absolute refractory period in the cardiac action potential cycle. During this time, some cardiac cells have partially recovered from the previous action potential and are in a state where they can respond to a stimulus. However, the threshold for generating another action potential is higher than during resting conditions.

This means that if a sufficiently strong impulse is applied during this period, it can reach the threshold necessary to trigger depolarization. This characteristic is crucial in understanding how the heart can be susceptible to arrhythmias, as it indicates a point where abnormal impulses can lead to potentially dangerous electrical activity in the heart. Other options do not accurately describe the condition of the cardiac cells during this specific phase of the action potential, as they either mischaracterize the ability to initiate depolarization or describe conditions that are not inherently linked to the relative refractory period.