Question

In which stage of cardiac cycle does the first sharp sound of the heart can be heard?

• A. Opening of the tricuspid valve or the bicuspid valve
• B. Contraction of atria
• C. Relaxation of atria
• D. Contraction of ventricles

Answer 1

The correct option is D Contraction of ventricles

On ventricular contraction, due to pressure, the blood moves into the aorta and pulmonary artery. The aperture between the atria and ventricles are closed by valves. When the valves are closed forcibly, the first sharp sound of the heart 'lub' can be heard. It is caused by the closure of mitral/bicuspid and tricuspid valves at the start of systole. 'Dub' sound is produced by the closure of aortic and pulmonary valves, marking the end of systole.