Normal heart sounds are caused by which of the following events?
A. excitation of the SA node
B. closure of the heart valves
C. friction of blood against the chamber walls
D. opening and closing of the heart valves
Answer:B
Normal heart sounds are caused by which of the following events?
A. excitation of the SA node B. closure of the heart valves C. friction of blood against the chamber walls D. opening and closing of the heart valves