QS Study

Changes that take place in 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. The time required for one complete cardiac cycle. For example:

  • If heart rate is 75, then cardiac cycle time will be = 60/70 second = 0.8 sec
  • The cardiac cycle time is inversely proportional to the heart rate.

The changes take places in cardiac cycle are:

(a) Changes in pressure

  • Intraventricular pressure change
  • Intra atrial pressure change
  • Pressure change within the aorta.
  • Pressure change within the pulmonary artery.

(b) Volume changes

  • Atrial volume change
  • Ventricular Volume Change

(c) Production of heart sound and apex beat.

(d) Production of pulse and appearance of the pulse wave.

(e) Electrical change.

(f) Electrocardiogram changes.

(g) Systemic, pulmonary, and coronary circulation changes.

The cardiac events that occur from the beginning of one heartbeat to the beginning of the next are called the cardiac cycle. During this cycle, blood is pumped out of the heart into the aorta and the pulmonary artery, and blood reenters the heart from the venae cavae and the pulmonary veins. Each cycle is initiated by spontaneous generation of action potential in the sinus node.