QS Study

Volume changes in ventricle during the cardiac cycle

The cyclical repetition of various changes in the heart in the same order from beat to beat is called cardiac cycle. It is the cycle of events that occurs when the heart beats. As the heart beats, it circulates blood through pulmonary and systemic circuits of the body.

Each ventricle, however, expels the same volume of blood per beat, and the similar outline exists for both pumping chambers. When the heart rate is 75 beats/min, a cardiac cycle lasts 0.8 sec.

The volume changes of the ventricles are to some extent the reverse of its pressure changes. The following phases are seen:

(i) During atrial systole, ventricular volume increases due to rapidly falling,

(ii) As soon as ejection starts, ventricular volume smoothly and continuously falls up to the end of systole.

(iii) In Isometric relaxation phase, volume remains same, because no blood is entering.

(iv) 1st rapid inflow phase ventricular filling starts and its volume rise rapidly.

(v) During slow inflow phase, ventricular volume very slowly increases.

Graph: Volume changes in ventricle

Volume changes during the cardiac cycle

Rt. ventricle

  • During systole: 15 – 30 mm of Hg.
  • During Diastole: 0 – 5 mm of Hg.

Lt. Ventricle

  • During Diastole: 04 – 12 mm of Hg.
  • During systole: 04 – 120 mm of Hg.