Trace the Order of Electrical Excitation of the Heart

Question

Trace the order of electrical excitation of the heart.
A) AV node, SA node, AV bundle, bundle branches
B) SA node, AV bundle, AV node, bundle branches
C) SA node, AV node, AV bundle, bundle branches
D) none of the above

Accepted Answer

The electrical excitation of the heart begins with the SA (sinoatrial) node, which is located in the right atrium. This node generates an electrical impulse that spreads throughout the atria, causing them to contract. The impulse then reaches the AV (atrioventricular) node, located in the lower part of the interatrial septum. The AV node delays the impulse slightly, allowing the atria to finish contracting before the ventricles are stimulated. From the AV node, the electrical impulse travels down the AV bundle (also known as the Bundle of His) and into the bundle branches. These branches distribute the impulse throughout the ventricles, causing them to contract. Therefore, the correct order is SA node, AV node, AV bundle, bundle branches, which is option C.