Cardiac Cycle Quiz: Valves, Pressures and Heart Sounds

Follow one heartbeat from ventricular filling through ejection and relaxation. Use pressure differences to explain when valves open and close, then connect those events with normal heart sounds.

8 questions · Estimated 6–8 minutes. Select your answer mentally, then open the explanation to check your reasoning.

1. During normal left ventricular isovolumetric contraction, what is the state of the mitral and aortic valves?

  1. Both valves are open
  2. Mitral open; aortic closed
  3. Both valves are closed
  4. Mitral closed; aortic open
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Answer: C. Both valves are closed

Both valves are closed. The mitral valve has closed because left ventricular pressure exceeds left atrial pressure, but ventricular pressure has not yet risen enough to open the aortic valve. Pressure rises while ventricular volume remains approximately constant.

2. In a normal heart, what pressure relationship opens the aortic valve and begins left ventricular ejection?

  1. Left ventricular pressure exceeds aortic pressure
  2. Left atrial pressure exceeds aortic pressure
  3. Aortic pressure exceeds left ventricular pressure
  4. Right ventricular pressure exceeds left atrial pressure
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Answer: A. Left ventricular pressure exceeds aortic pressure

The aortic valve opens when left ventricular pressure exceeds aortic pressure. Valves respond passively to pressure gradients; they do not open through their own muscular contraction.

3. Immediately after the aortic valve closes, before the mitral valve opens, what normally happens in the left ventricle?

  1. Pressure rises while volume falls
  2. Pressure and volume both rise
  3. Volume rises while pressure remains fixed
  4. Pressure falls while volume remains approximately constant
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Answer: D. Pressure falls while volume remains approximately constant

This is isovolumetric relaxation. Both the aortic and mitral valves are closed, so ventricular volume remains approximately constant while myocardial relaxation lowers ventricular pressure. Filling begins after the mitral valve opens.

4. Which pressure relationship normally opens the mitral valve at the start of left ventricular filling?

  1. Left ventricular pressure exceeds aortic pressure
  2. Left atrial pressure exceeds left ventricular pressure
  3. Aortic pressure exceeds left atrial pressure
  4. Right atrial pressure exceeds left ventricular pressure
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Answer: B. Left atrial pressure exceeds left ventricular pressure

As the left ventricle relaxes, its pressure falls below left atrial pressure. This gradient opens the mitral valve and drives blood into the ventricle. The aortic valve remains closed during normal ventricular filling.

5. The first heart sound, S1, is primarily associated with which event?

  1. Opening of the aortic and pulmonary valves
  2. Opening of the mitral and tricuspid valves
  3. Closure of the mitral and tricuspid valves
  4. Closure of the aortic and pulmonary valves
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Answer: C. Closure of the mitral and tricuspid valves

S1 is associated with AV valve closure at the beginning of ventricular systole. The sound reflects vibrations of the valve apparatus, blood and surrounding cardiac structures. Semilunar valve closure is associated with S2.

6. The second heart sound, S2, is primarily associated with which event?

  1. Closure of the aortic and pulmonary valves
  2. Opening of the aortic and pulmonary valves
  3. Closure of the mitral and tricuspid valves
  4. Atrial contraction opening the AV valves
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Answer: A. Closure of the aortic and pulmonary valves

S2 is associated with aortic and pulmonary valve closure at the end of ventricular ejection, marking the transition to ventricular diastole. Normal valve opening is generally silent.

7. When does the left ventricle normally contain its end-diastolic volume?

  1. At the end of ventricular ejection
  2. Only while the aortic valve is open
  3. At the start of rapid ventricular filling
  4. At the end of filling, just before ventricular systole
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Answer: D. At the end of filling, just before ventricular systole

End-diastolic volume is the blood volume in the ventricle after filling is complete, just before systole. That volume is maintained during isovolumetric contraction until ejection begins. End-systolic volume is the volume remaining after ejection.

8. In a healthy adult at rest, most ventricular filling normally occurs:

  1. During ventricular ejection
  2. Passively during diastole, before atrial contraction
  3. Only during atrial contraction
  4. During isovolumetric contraction
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Answer: B. Passively during diastole, before atrial contraction

Most resting ventricular filling occurs passively after the AV valves open. Atrial contraction adds blood late in diastole. Its contribution becomes more important when ventricular relaxation or compliance is impaired and can vary with heart rate.

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