What does systole refer to?

Systole refers specifically to the phase of the cardiac cycle when the heart muscles contract, which in turn increases the pressure within the arteries as blood is pumped out from the heart. During systole, the ventricles contract, ejecting blood into the aorta and pulmonary arteries, which is crucial for maintaining blood circulation throughout the body.

Understanding systole is important in the context of cardiovascular health, as elevated pressure during this phase can indicate conditions such as hypertension. This phase is contrasted with diastole, during which the heart relaxes and fills with blood, leading to the opposite state of pressure in the arteries. The other provided options do not accurately describe systole; for instance, the reference to pressure during rest pertains to diastolic pressure, while blood flow to the lungs is related to the right side of the heart during various phases of the cardiac cycle.