What is the Cause of the Heart Sounds "Lubb-Dupp

Question

What is the cause of the heart sounds "lubb-dupp"?
A) Closing of the heart valves
B) Flow of blood through the coronary arteries
C) The electrical signal as it moves through the AV node
D) The firing of the autonomic nerves to the SA node

Accepted Answer

The heart sounds "lubb-dupp" are caused by the closing of the heart valves. Specifically, the first sound "lubb" is caused by the closing of the mitral and tricuspid valves at the start of systole, while the second sound "dupp" is caused by the closing of the aortic and pulmonary valves at the end of systole.