Long Refractory period - Properties of a Beating Heart

Refractory period is the period during which a stimulus fails to evoke a response. In a beating heart, if an external stimulus is applied during contraction, there is no response irrespective of how strong the stimulus is. This is because the cardiac muscle is refractory throughout the contraction.  The reason why cardiac muscle has a long refractory period is t3at the duration of its action potential is almost as long as that of its mechanical activity. The fact that the heart sleeps and does not reacts when exposed to day-to-day exciting and stressful situations without missing a heartbeat every now and then ensures its smooth functioning hundred long years.