The  cardiac cycle  is the performance of the  human heart  from the beginning of one heartbeat to the beginning of the next. It consists of two periods: one during which the heart muscle relaxes and refills with blood, called  diastole  ( / d aɪ ˈ æ s t ə l i / ), followed by a period of robust contraction and pumping of blood, dubbed  systole  ( / s ɪ s ˈ t ə l i / ). After emptying, the heart immediately relaxes and expands to receive another influx of blood  returning from  the lungs and other systems of the body, before again contracting to  pump blood to  the lungs and those systems. A normally performing heart must be fully expanded before it can efficiently pump again. Assuming a healthy heart and a typical rate of 70 to 75 beats per minute, each cardiac cycle, or heartbeat, takes about 0.8 seconds to complete the cycle. [2]   Cardiac cycle   Organisms Animalia *  Biological system Circulatory system  Health Beneficia...