The Cardiac Cycle

The Cardiac Cycle - The Cardiac Cycle

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The Cardiac Cycle The cardiac cycle describes all the activities of the heart through one complete heartbeat—that is,  through one contraction and relaxation of both the atria and ventricles. A contraction event (of either  the atria or ventricles) is referred to as  systole,  and a relaxation event is referred to as  diastole.  The  cardiac cycle includes a description of the systolic and diastolic activities of the atria and ventricles,  the blood volume and pressure changes within the heart, and the action of the heart valves. A  description of each period of the cardiac cycle follows:  The isovolumetric ventricular relaxation is the period during which the ventricles are relaxed  and both AV and semilunar valves are still closed. The volume of the ventricles remains  unchanged (isovolumetric) during this period. Ventricular filling begins as the AV valves open and blood fills the ventricles. The 
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The Cardiac Cycle - The Cardiac Cycle

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