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# Cardiac Cycle The text describes the three stages of the cardiac cycle: ## Three Stages of Cardiac Cycle * **Atrial Systole** * Atria contract, pumping blood into ventricles. * AV valves are open, ventricles are relaxed. * **Ventricular Systole** * Ventricles contract, pushing AV v...

# Cardiac Cycle The text describes the three stages of the cardiac cycle: ## Three Stages of Cardiac Cycle * **Atrial Systole** * Atria contract, pumping blood into ventricles. * AV valves are open, ventricles are relaxed. * **Ventricular Systole** * Ventricles contract, pushing AV valves closed. * Semilunar valves open. * Blood is pumped to the pulmonary artery and aorta. * **Diastole** * Brief period where both atria and ventricles are relaxed. * Blood flows into the atria; some passively flows into ventricles. * Diastole is the filling period. ### Definitions: * **Systole:** Contraction of heart muscle, forcing blood out of the chamber. * **Diastole:** Relaxation of heart muscle, allowing the chamber to fill with blood.