Multiple Choice
Which two values are required to calculate cardiac output (CO) for a ventricle?
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18. The Heart
Cardiac Cycle
Multiple Choice
During the isovolumetric relaxation phase of the cardiac cycle, which of the following occurs?
A
The atrioventricular valves are open and blood flows into the ventricles.
B
The semilunar valves are open and blood is ejected from the ventricles.
C
All heart valves are closed and ventricular pressure is decreasing.
D
Ventricular pressure is increasing as the ventricles contract.
Verified step by step guidance1
Understand the cardiac cycle phases: The cardiac cycle consists of systole (contraction) and diastole (relaxation). Isovolumetric relaxation occurs during early diastole, right after ventricular systole.
Define isovolumetric relaxation: During this phase, the ventricles are relaxing, but the volume of blood within them remains constant because all heart valves are closed.
Analyze the pressure changes: As the ventricles relax, the pressure inside them decreases. This is a key characteristic of the isovolumetric relaxation phase.
Evaluate the state of the valves: During isovolumetric relaxation, both the atrioventricular (AV) valves and semilunar valves are closed. This prevents blood flow into or out of the ventricles during this phase.
Confirm the correct description: Based on the above analysis, the correct description of the isovolumetric relaxation phase is 'All heart valves are closed and ventricular pressure is decreasing.'
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