Describe the way in which high blood pressure and a defective semilunar valve can make it more difficult for the heart to pump blood into the systemic circulation and how these factors can decrease cardiac output. Include the following in your answer : afterload, period of isovolumetric contraction, stenosis, and blood flow resistance
What will be an ideal response?
High blood pressure means that the afterload on the heart is higher than normal, which means the ventricles must pump more forcefully to open the semilunar valves. When the ventricle begins systole, the higher afterload will cause the semilunar valves to stay closed longer, which means the period of isovolumetric contraction will last longer. This leaves less time for ventricular ejection to occur when the semilunar valve finally opens; consequently, the cardiac output can decrease. Stenosis means that a valve does not open completely, which means that during ventricular ejection the total amount of blood ejected will be less than what would occur if the valve openly freely and all the way.
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