Physiology MCQ Answer 98

The Right Answer is A

Pulse pressure = SP - DP. The pulse pressure is felt as a throb at the wrist or neck, and the rate of these (pulse rate) gives a measure of heart rate, since each pulse corresponds to a heart beat. Heart rhythm and the pulse magnitude can also be assessed by ‘taking someone’s pulse’.

The rise in aortic pressure from its diastolic to systolic value is determined by the compliance of the aorta as well as the ventricular stroke volume. In the arterial system, the aorta has the highest compliance, due in part to a relatively greater proportion of elastin fibers versus smooth muscle and collagen. This serves the important function of dampening the pulsatile output of the left ventricle, thereby reducing the pulse pressure (systolic minus diastolic arterial pressure). If the aorta were a rigid tube, the pulse pressure would be very high. Because the aorta is compliant, as blood is ejected into the aorta, the walls of the aorta expand to accommodate the increase in blood volume. As the aorta expands, the increase in pressure is determined by the compliance of the aorta at that particular range of volumes. The more compliant the aorta, the smaller the pressure change during ventricular ejection (i.e., smaller pulse pressure). Therefore, aortic compliance is a major determinant, along with stroke volume, of the pulse pressure.

Category: Physiology MCQs