Systole is defined as which of the following?

Systole refers to the phase of the cardiac cycle during which the heart muscle contracts and pumps blood out of the chambers. This contraction occurs first in the atria, propelling blood into the ventricles, followed by ventricular contraction, which sends blood from the heart to the lungs and the rest of the body. This process is vital for maintaining circulation and ensuring that all tissues receive oxygenated blood.

The understanding of systole is critical in neonatal care, as the heart's ability to contract effectively influences the overall hemodynamic status of the newborn. Monitoring systolic blood pressure and heart function is essential for assessing the baby's cardiac output and stability.

In contrast, the other options describe different aspects of the cardiac cycle or physiological processes. The period of heart relaxation is known as diastole, the time between heartbeats refers to the heart rate intervals, and the closure of the aortic valve occurs at the end of ventricular systole but does not define the contraction itself. This distinction underscores the importance of terminology in understanding cardiac physiology.