Each part of the cardiac cycle consists of several phases characterized by either a strong pressure change with constant volume or a volume change with a relatively small change in pressure.
4.Rapid ventricular filling.
5.Slow ventricular filling (diastasis).
The duration of the cardiac cycle is inversely proportional to the heart rate. The cardiac cycle duration increases with a decrease in the heart rate and on the other hand it shortens with increasing heart rate. At a normal heart rate of 75 beats per minute, one cardiac cycle lasts 0.8 second. Under resting conditions, systole occupies ⅓ and diastole ⅔ of the cardiac cycle duration. At an increasing heart rate (e.g. during an intensive muscle work), the duration of diastole decreases much more then the duration of systole.