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The cardiac cycle
Member rating: No Rating | Words: | Submitted: Tue Aug 12 2003
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The cardiac cycle The cardiac cycle is the sequence of events that occur when the heart beats. There are two phases of this cycle: * Diastole - Ventricles are relaxed. * Systole - Ventricles contract. During the diastole phase the atria and ventricles are relaxed and the atrioventricular valves are open. De-oxygenated blood from the superior and inferior vena cava flows into the right atrium. The open atrioventricular valves allow blood to pass through to the ventricles. The SA node contracts triggering the atria to contract. The right atrium empties its contents into the right ventricle. The tricuspid valve prevents the blood from flowing back into the right atrium. During the systole phase the right ventricle receives impulses from the Purkinje fibers and contracts. The atrioventricular valves close and the semilunar valves open. The de-oxygenated blood is pumped into the pulmonary artery. The pulmonary valve prevents the blood from flowing back into...
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