What is the definition of diastole?

The correct definition of diastole refers to the phase of the heartbeat when the heart muscle relaxes. During this phase, the chambers of the heart fill with blood. After the contraction or systole, which propels blood out of the heart, the muscle fibers of the heart (myocardium) relax, allowing for the chambers to expand and receive blood from the returning veins. This relaxation phase is crucial for ensuring that there is adequate blood volume for subsequent contractions and for maintaining an efficient and effective circulation.

In contrast, the other options relate to different aspects of cardiac physiology. The contraction phase of the heart, known as systole, refers specifically to when the heart muscles are actively pushing blood out. The terms for maximum and minimum arterial pressure are not directly related to diastole itself, but rather to the concepts of systolic and diastolic blood pressure, which describe the highest and lowest pressures in the arteries thought to be associated with heartbeats. Understanding the phases of the cardiac cycle, including diastole and systole, is essential for comprehending how the heart functions and maintains circulation.