Question

Which one of the following is a correct matching pair?

• A. Lub - sharp closure of AV valves at the beginning of ventricular systole
• B. Dub - sudden opening of semilunar valves at the beginning of ventricular diastole
• C. Pulsation of the radial artery - valves in the blood vessels
• D. Initiation of the heart beat - Purkinje fibres

Answer 1

The correct option is A Lub - sharp closure of AV valves at the beginning of ventricular systole

During the begining of ventricular systole, the contraction of ventricular muscles causes the closure of bicuspid and tricuspid valves (AV valves) producing 'lub' sound. At the end of ventricular systole, semilunar valves close producing the second heart sound, the 'dub'.

Pulsation of the radial artery is due to rhythmic contraction and relaxation in the aorta.

Initiation of the heart beat occurs in the SA node.