Cardiac Cycle

Multiple Choice Questions (MCQs)

1. What is the total duration of the cardiac cycle at a heart rate of 75 beats/min?
   a) 0.5 seconds
   b) 0.8 seconds
   c) 1.0 seconds
   d) 1.2 seconds
   Answer: b) 0.8 seconds
2. During ventricular systole, the atria are in which phase?
   a) Systole
   b) Diastole
   c) Isovolumetric contraction
   d) Reduced ejection
   Answer: b) Diastole
3. Which event corresponds to the ‘a’ wave in atrial pressure changes?
   a) Ventricular ejection
   b) Atrial systole
   c) Ventricular relaxation
   d) Closure of semilunar valves
   Answer: b) Atrial systole
4. What is the primary event during isovolumetric contraction?
   a) AV valves open, allowing ventricular filling.
   b) Ventricular pressure rises with no volume change.
   c) Rapid ejection of blood into the aorta.
   d) Opening of semilunar valves.
   Answer: b) Ventricular pressure rises with no volume change.
5. What happens during the protodiastole phase?
   a) Rapid ventricular filling occurs.
   b) Atrial contraction begins.
   c) Semilunar valves close as ventricular pressure drops.
   d) AV valves open, allowing blood to flow into ventricles.
   Answer: c) Semilunar valves close as ventricular pressure drops.
6. Which ventricular pressure is higher during systole?
   a) Right ventricle
   b) Left ventricle
   c) Both are equal
   d) Neither has pressure during systole
   Answer: b) Left ventricle
7. What is the duration of atrial systole in a cardiac cycle at 75 beats/min?
   a) 0.1 seconds
   b) 0.3 seconds
   c) 0.5 seconds
   d) 0.7 seconds
   Answer: a) 0.1 seconds
8. What occurs during the maximum ejection phase of the cardiac cycle?
   a) AV valves open.
   b) Rapid outflow of blood from ventricles.
   c) Ventricular pressure drops below atrial pressure.
   d) Semilunar valves close.
   Answer: b) Rapid outflow of blood from ventricles.
9. What is the peak systolic pressure range of the left ventricle?
   a) 20–40 mmHg
   b) 60–80 mmHg
   c) 100–160 mmHg
   d) 180–200 mmHg
   Answer: c) 100–160 mmHg
10. What marks the end of the isovolumetric relaxation phase?
    a) Opening of AV valves
    b) Closure of semilunar valves
    c) Onset of ventricular contraction
    d) Peak intraventricular pressure
    Answer: a) Opening of AV valves

Fill in the Blanks

1. The ________ valves close during isovolumetric contraction.
   Answer: AV
2. Atrial systole contributes an additional ________% of blood to ventricular filling.
   Answer: 20–30
3. The ________ wave in atrial pressure occurs due to bulging of the AV valves during ventricular systole.
   Answer: ‘c’
4. Protodiastole is the phase during which the semilunar valves ________.
   Answer: close
5. The ________ ventricle functions as a pressure pump, while the ________ ventricle functions as a volume pump.
   Answer: left, right

True or False

1. During atrial diastole, the atria are actively contracting.
   Answer: False
2. The duration of ventricular diastole is longer than ventricular systole.
   Answer: True
3. The ‘v’ wave in atrial pressure is caused by continuous blood inflow into the atria during ventricular ejection.
   Answer: True
4. Both ventricles eject blood simultaneously during the maximum ejection phase.
   Answer: True
5. The right ventricle has a higher systolic pressure than the left ventricle.
   Answer: False

Subjective Questions

1. Explain the significance of the isovolumetric contraction phase in the cardiac cycle.
   Answer:
   The isovolumetric contraction phase begins with the onset of ventricular contraction. During this phase, the AV valves close due to rising ventricular pressure, but the semilunar valves remain closed. This results in no change in ventricular volume while the pressure rises rapidly. This phase ensures that the ventricles develop sufficient pressure to open the semilunar valves and eject blood into the aorta and pulmonary artery during the subsequent ejection phases.
2. Compare the functions of the right and left ventricles in terms of pressure and volume during the cardiac cycle.
   Answer:
   • Right Ventricle: Functions as a volume pump, generating lower pressures (20–40 mmHg) to propel blood through the pulmonary circulation. It manages a lower resistance environment compared to the systemic circulation.
   • Left Ventricle: Functions as a pressure pump, generating higher pressures (100–160 mmHg) to ensure blood is ejected into the systemic circulation against greater resistance.
     These differences reflect the distinct roles of the pulmonary and systemic circuits in maintaining efficient blood flow throughout the body.