Which of the following terms describes the heart's relaxation phase?

The term that describes the heart's relaxation phase is 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 proper cardiovascular function as it ensures there is enough blood in the heart to be pumped out during the following contraction phase, known as systole.

In the context of the other terms, systole refers to the contraction phase of the heart where blood is forcefully expelled from the heart chambers, which is the opposite of relaxation. Cardiac arrest is a medical emergency that occurs when the heart stops beating effectively, preventing blood flow throughout the body. Arrhythmia describes irregular heartbeats and variations in the heart's rhythm, which is not directly related to the relaxation phase itself. Understanding these terms helps clarify the cyclical nature of the cardiac cycle, which involves alternating phases of contraction and relaxation to maintain effective blood circulation.