Question

The CORRECT order of duration of various phases of the cardiac cycle is

• A. Atrial systole < Ventricular systole < Joint diastole < Ventricular diastole < Atrial diastole
• B. Atrial systole < Ventricular diastole < Joint diastole < Ventricular systole < Atrial diastole
• C. Atrial diastole < Ventricular diastole < Joint diastole < Ventricular systole < Atrial systole
• D. Joint diastole < Ventricular diastole < Atrial diastole

Answer 1

Answer: (A)

The action potential generated by the SA node stimulates both the atria to contract, which is known as the atrial systole. This action potential is then transmitted to the ventricles by the AV node and the Bundle of His, which makes the ventricular musculature to contract. Both the atria and ventricles then are in a state of relaxation called the joint diastole which is then followed by the ventricular relaxation, when the blood from the ventricles flow into the pulmonary artery and aorta. The aortic diastole takes place at the end of the cycle wherein the blood from the atria are pushed into the ventricles due to the opening of the tricuspid and bicuspid valves.
A rhythmic contraction and relaxation of heart during one heartbeat is called the cardiac cycle. The time required for one cardiac cycle is 0.8sec.