The Hear2 - flows into the aorta Heart Sounds • The first...

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The Heart Electrocardiogram o The ECG is a record of electrical events within the heart. o The ECG can be used to detect abnormal heart rates or rhythms, conduction pathways, hypertrophy or atrophy of the heart, and the approximate location of damaged cardiac muscle. o The normal ECG consists of a P wave (atrial depolarization), a QRS complex (ventricular depolarization), and a T wave (ventricular repolarization). o Atrial contraction occurs during the P-Q interval, and the ventricles contract and relax during the Q-T interval. Cardiac Cycle Atrial systole is contraction of the atria, and ventricular systole is contraction of the ventricles. Atrial diastole is relaxation of the atria, and ventricular diastole is relaxation of the ventricles. During atrial systole, filling of the right ventricle is completed. During ventricular systole, the tricuspid valve closes, and blood forces open the pulmonary semilunar valve; blood flows into the pulmonary trunk. Also, the bicuspid valve closes, and blood forces open the aortic semilunar valve; blood
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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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