To Evaluate Cardiac Function, Scientists and Physicians Measure Both the Pressure

question 71

Multiple Choice

To evaluate cardiac function, scientists and physicians measure both the pressure and the volume inside the heart. When both pressure and volume data are plotted on the same graph, the resulting graph is called a pressure-volume loop. To create a pressure-volume loop, a catheter (a thin tube) is inserted into the vessels of the heart, and measurements of both left ventricular pressure and left ventricular volume are taken. The data are plotted on a graph, and cardiac function can then be evaluated from the distribution of the data and the shape of the loop.
The following figure shows a typical left ventricle pressure-volume loop for a healthy young adult. The cardiac cycle proceeds counterclockwise. Each complete turn around the loop (for example, starting at point A and ending back at point A) represents one complete cardiac cycle.

-At what point on the diagram does the aortic valve (the semilunar valve that separates the left ventricle and the aorta) open?

• A) point A
• B) point B
• C) point C
• D) point D

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