What does systole refer to in cardiac physiology?

Systole refers specifically to the contraction phase of the heart cycle. During systole, the heart's ventricles contract to pump blood out of the heart; the left ventricle pushes oxygen-rich blood into the aorta and out to the body, while the right ventricle sends deoxygenated blood to the lungs for oxygenation. This contraction is a vital part of maintaining effective blood circulation throughout the body.

Understanding systole in this context is important for grasping the overall function of the cardiac cycle, which alternates between contraction (systole) and relaxation (diastole). It's essential for students studying cardiac physiology to recognize that systole is primarily concerned with the action of the heart contracting rather than any other processes such as filling the heart chambers or the electrical stimulation.

In contrast, filling of the heart chambers occurs during diastole, when the heart muscle relaxes and allows blood to flow into the atria and subsequently into the ventricles. Relaxation of the heart, also part of diastole, is necessary for the chambers to refill with blood. Electrical stimulation refers to the heart's electrical conduction system that initiates the contraction, but it does not define systole itself; rather, it triggers it. Therefore,