The cardiac cycle consists of two phases; a period where the heart muscle is relaxed, called diastole, and a period of contraction, called systole.
These are then divided into four stages. These are;
1. Ventricular Filling Period (VPF)
2. Isovolumetric Contraction Period (ICP)
3. Ventricular Ejection Period (VEP)
4. Isovolumetric Relaxation Period (IRP)
At rest, cardiac diastole lasts for approximately 0.5 seconds, and cardiac systole lasts approximately 0.3 seconds to complete. However, during exercise, when the heart rate is increased the time period of diastole , especially, is reduced.
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