Briefly discuss the cardiac cycle. Include the time of the phases and what occurs in the atria and the ventricles. Define and use the terms systole and diastole.
What will be an ideal response?
Systole refers to the contraction of the heart chambers and diastole refers to the relaxation of heart chambers. In the cardiac cycle, first the atria contract while the ventricles relax. Next, the ventricles contract while the atria relax. This is followed by all chambers relaxing. The heart is in diastole almost half the time, about 0.4 seconds. The short systole of the atria, about 0.15 seconds, is appropriate, since the atria only pump blood to the ventricles. However, the systole of the ventricle is longer, about 0.30 seconds, since the ventricles actually pump the blood out of the heart into the rest of the cardiovascular system. A normal cardiac cycle, or heartbeat, takes about 0.85 seconds.
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