systol

Systol is not a standard term in English medical nomenclature. In most texts, the contraction phase of the cardiac cycle is called systole. When used, systol is often an informal or abbreviated form of systole. Systole refers to the period during which the heart muscle contracts to pump blood. The cardiac cycle includes systole and diastole, the latter being the relaxation phase when the heart fills with blood.

During ventricular systole, the ventricles contract. This raises the pressure inside the ventricles, closing the atrioventricular valves and opening the semilunar valves, allowing ejection of blood into the aorta and pulmonary artery. Atrial systole does occur earlier but is typically considered separate; it finishes ventricular filling and contributes to end-diastolic volume.

Systolic blood pressure is the maximum arterial pressure during systole and is recorded as the top number in a blood pressure reading (for example, 120/80 mmHg). Diastolic pressure is the minimum arterial pressure during diastole. Normal resting systolic pressure typically ranges around 90 to 120 mmHg in adults, with higher values indicating potential hypertension, and lower values potentially indicating hypotension.

The term is used in various contexts including cardiology, physiology, and medical imaging. In clinical practice, abnormalities in systolic function include impaired ventricular contraction, reduced ejection fraction, and systolic heart failure. Etymology: from Greek systole meaning "constriction, contraction." The opposite term is diastole.