Question

Explain cardiac cycle with the help of diagrams.

Answer 1

• The cardiac cycle is the performance of the human heart, beginning from one heartbeat to the beginning of the next.
  
• It consists of two phases:- 1) Diastolic phase, 2) Systolic phase.
• In the diastolic phase, the heart ventricles are relaxed and the heart fills with blood.
• In the systolic phase, the ventricles contract and pump blood out of the heart and to arteries.
• It further proceeds in the following steps:
• Atrial systole lasts about 0.1 seconds - both atria contract and forces the blood from the atria into the ventricles.

• Ventricular systole lasts about 0.3 seconds - both ventricles contract, blood is forced to the lungs via the pulmonary trunk and the rest of the body via the aorta.
• Atrial diastole lasts for about 0.7 seconds- relaxation of the atria, during which the atria fill with blood from the large veins (the vena cavae).
• Ventricular diastole lasts about 0.5 seconds - begins before atrial systole, allowing the ventricles to fill passively with blood from the atria.