Question

Which of the following events do not occur during joint diastole?

(I) All four–chambers are in relaxed state

(II) Tricuspid and bicuspid are open

(III) Semilunar valves are closed

(IV) Blood from the pulmonary veins and vena cava flows into the left and right ventricles, respectively through the left and right atria

• A.
  Only I
• B.
  Only II
• C.
  II and IV
• D.
  None of these

Answer 1

The correct option is D

None of these
The cardiac cycle begin with when all the four chambers of heart are in a relaxed state, i.e., they are in joint diastole. As the tricuspid and bicuspid valves are open, blood from the pulmonary veins and vena cava flows into the left and the right ventricle respectively through the left and right atria. The semilunar valves are closed at this stage. The (sino-articular node) SAN now generates an action potential which stimulates both the atria to undergo a simultaneous contraction called the atrial systole.