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Unformatted text preview: flows into the aorta. Heart Sounds The first heart sound results from closure of the tricuspid and bicuspid valves. The second heart sound results from closure of the aortic and pulmonary semilunar valves. Abnormal heart sounds are called murmurs. They can result from incompetent (leaky) valves or stenosed (narrowed) valves. Regulation of Heart Function Cardiac output (volume of blood pumped per ventricle per minute) is equal to the stroke volume (volume of blood ejected per beat) times the heart rate (beats per minute). Intrinsic Regulation of the Heart o Intrinsic regulation refers to regulation that is contained in the heart. o As venous return to the heart increases, the heart wall is stretched, and the increased stretch of the ventricular walls is called preload. o An increase in preload causes the stroke volume to increase (Starling's law of the heart) and heart rate to increase. o Afterload is the pressure against which the ventricles must pump blood....
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- Fall '10