Correct Answer - D
The action potential is conducted to the ventricular side by the AVN and AV bundle from where the bundle of His transmits it through the entire ventricular mussculate.
This causes the ventricular muscle to contract, (ventricular systtole), the atria undergoes relaxtion (diastole), cinciding with the ventriculary systole.
Ventricular systole increases the ventricular pressure causing the closure of tricuspid and bicspid valves due to attempted backflow of blood into the atria.
As the ventricular pressure increases further, the semilunar valves guarding the pulmonary artery (right side) and the aorta (left side) are forced open, allowing the blood in the ventricles to flow through these vessels into the circulatory pathways.
During ventricular systole bicuspid and tricuspid valve become closed while semilunar valves are forced open.
