During which phase of the cardiac cycle does the heart muscle relax?

The heart muscle relaxes during diastole, which is the phase of the cardiac cycle that follows contraction. During diastole, the heart chambers fill with blood as the pressure in the atria becomes greater than in the ventricles. This relaxation allows the cardiac muscle fibers to return to their resting state, enabling efficient filling of the heart with blood. Proper relaxation during this phase is essential to maintain an effective cardiac output and ensure that enough blood is available to pump to the body during the next contraction.

Systole, atrial contraction, and ventricular contraction all refer to phases of the cardiac cycle when the heart muscle is actively contracting to pump blood out of the heart or into the ventricles. In contrast, diastole is specifically characterized by the relaxation of the heart muscle. Understanding this distinction is crucial for recognizing the dynamics of blood flow and heart function during each phase of the cycle.