Question

Lub sound is due to ______________

• A. closing of semilunar valve
• B. opening of semilunar valve
• C. closing of atrioventricular valve
• D. opening of atrioventricular valve

Answer 1

The correct option is C closing of atrioventricular valve

In a cardiac cycle, the atrial systole takes place by the help of the sinoatrial node that generates an action potential due to which the left and right atrium contracts.
The action potential is then further conducted to the atrioventricular node. Then it is conducted to the bundle of His and purkinje fibres. Due to the transmission of the action potential, the ventricles contract called ventricular systole.
At this stage, the atria relax and undergo diastole. Due to the ventricular systole, the pressure inside the ventricles increases which results in closure of the atrioventricular valve. Lub sound is produced due to the closure of the (atrioventricular valve). The valves present between the atrium and ventricles are called atrioventricular valves.