ZoologyIn the heart, as the action potential reaches from the SA node to the AV node, the action potential slows considerably at the AV node. This delay provides time for

In the heart, as the action potential reaches from the SA node to the AV node, the action potential slows considerably at the AV node. This delay provides time for

A
atria to empty their blood into the ventricles
B
ventricles to complete their systole
C
atria to recover from muscle fatigue
D
semilunar valves to open completely

Solution:

Cardiac excitation normally begins in the SA node. By conducting along atrial muscle fibres, the action potential reaches the AV node. At the AV node, the action potential slows considerably. This delay provides time for the atria to empty their blood into the ventricles. During this time, the ventricles are in a diastole and the semilunar valves are closed.