What is the duration of the refractory period in milliseconds during the action potential of cardiac muscle cells?

The refractory period in cardiac muscle cells is a critical phase during which the cells are unable to respond to a second stimulus after an initial action potential. This period is essential for maintaining a proper rhythmic contraction of the heart, as it prevents tetany, which is a sustained contraction that can occur if the muscle fibers are stimulated too frequently.

The refractory period lasts approximately 250 milliseconds in cardiac muscle cells. This duration allows for adequate time for the muscle to contract and relax completely, ensuring effective pumping of blood. Moreover, the prolonged refractory period contributes to the unique functionality of cardiac tissue, allowing for the heart to fill with blood before the next contraction occurs, thereby supporting efficient circulation.

Understanding this duration is essential for comprehending how electrical signals in the heart control its rhythm and overall function. The other durations listed do not align with the physiological characteristics of cardiac cells, as they either fall below or exceed the typical refractory period observed in cardiac tissues.