Figure 18-2 Cardiac Cycle
Use Figure 18-2 to answer the following questions:
-What occurs at the circled label "4" on the graph?
A) peak systolic pressure
B) isovolumetric systole
C) isovolumetric contraction
D) ventricular refilling
E) increased heart rate

Question

Figure 18-2 Cardiac Cycle
Use Figure 18-2 to answer the following questions:
-What occurs at the circled label "4" on the graph?
A) peak systolic pressure 
B) isovolumetric systole 
C) isovolumetric contraction 
D) ventricular refilling 
E) increased heart rate

Quizplus · Accepted Answer

The circled label "4" on the graph represents isovolumetric contraction, which is the phase in the cardiac cycle where the ventricles are contracting but the volume of blood in the chambers is not changing. This occurs after the mitral valve closes and before the aortic valve opens. Option A is incorrect because peak systolic pressure occurs during ventricular ejection, which is represented by the rise in pressure after the aortic valve opens. Option B is incorrect because isovolumetric systole occurs between labels "2" and "3," when the ventricles are contracting but the semilunar valves are closed, causing an increase in pressure but no change in volume. Option D is incorrect because ventricular refilling occurs during diastole and is represented by the drop in pressure and increase in volume after the aortic valve closes. Option E is incorrect because increased heart rate is not represented or indicated on this graph.