Cardiac Cycle - Stages of The Cardiac Cycle

Stages of The Cardiac Cycle

	AV valves*	Semilunar valves†	Status of ventricles and atria
1. early diastole	open	closed	• whole heart is relaxed • ventricles are expanding and filling
2. atrial systole	open	closed	• atria contract and pump blood • additional 10–40% filling of ventricles
3. isovolumic ventricular contraction	closed	closed	• ventricular myocytes begin to contract • ventricle volume unchanged
4. ventricular ejection	closed	open	• ventricles fully contract • pump blood to rest of body
5. Isovolumic ventricular relaxation	closed	closed	• ventricles relax • ventricle volume unchanged • atria expand and are filling

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