HESI A2 Anatomy and Physiology Practice Exam 2025 – Comprehensive All-in-One Guide to Exam Success!

The relaxation phase of the cardiac cycle is referred to as diastole. During diastole, the heart muscles relax, allowing the chambers of the heart, specifically the atria and ventricles, to fill with blood. This phase is crucial for effective circulation, as it prepares the heart to pump blood efficiently during the subsequent contraction phase, known as systole.

At this stage, the heart experiences a decrease in pressure allowing the mitral and tricuspid valves to open, enabling blood to flow from the atria to the ventricles. In contrast, systole refers to the contraction phase where the heart pumps blood out to the body. Isovolumetric relaxation is a specific aspect of diastole but does not encompass the entire relaxation phase of the cardiac cycle. The term "atria phase" is not a recognized phase in the standard terminology of the cardiac cycle. Thus, diastole aptly captures the entire process of relaxation that is critical for the heart's function.