Definitions for "Cardiac cycle"
One complete heartbeat, seen on the ECG as a P wave, a QRS complex and a T wave. In a normal cardiac cycle, the atria depolarize and contract, delivering blood into the relaxed ventricles (P wave); the atria repolarize and relax while the ventricles, now filled to capacity with blood, contract and pump blood into the systemic and pulmonary circulation systems (QRS complex). After the ventricular contraction, the ventricles repolarize and relax (T wave). The cycle begins again at the end of ventricular repolarization with the onset of passive ventricular filling.
one complete cycle of the three stages of heart action.
describes all the activities of the heart through one complete heartbeat - that is, through one contraction and relaxation of both the atria and the ventricles.