In the cardiac cycle, which term describes the phase of active contraction of the heart muscle?

The term that describes the phase of active contraction of the heart muscle is systole. During systole, the heart muscle contracts to pump blood out of the chambers—first from the atria into the ventricles during atrial systole, and then from the ventricles into the arteries during ventricular systole. This contraction is crucial for maintaining effective blood circulation throughout the body.

In contrast, diastole refers to the relaxation phase of the cardiac cycle when the heart fills with blood. Atrial contraction pertains specifically to the contraction of the atrial chambers, which occurs within the systolic phase but does not encompass the entire contraction process of the heart muscle. Ventricular dilation describes the chamber’s capacity to fill with blood when it is relaxed, which occurs during diastole and is not related to the contraction phase.