Where Does the Cardiac Action Potential (Cardiac Impulse)normally Originate

Question

Where does the cardiac action potential (cardiac impulse)normally originate?
A) AV node
B) Purkinje fibers
C) Ectopic focus
D) SA node

Accepted Answer

The SA (sinoatrial) node normally originates the cardiac impulse, which acts as the heart's natural pacemaker. The other options (AV node, Purkinje fibers, ectopic focus) may also have the ability to initiate a cardiac impulse, but they are not the normal site of origin.