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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