Question

The following are structural components of the conducting system of the heart.

1. Purkinje fibers
2. AV bundle
3. AV node
4. SA node
5. bundle branches
The sequence in which excitation would move through this system is which of the following?

Answer 1

The correct sequence of excitation in the heart's conducting system starts at the SA node, goes through the internodal pathways to the AV node, then to the AV bundle, into the bundle branches, and finishes with the Purkinje fibers.

Step-by-step explanation:

The sequence in which excitation moves through the conducting system of the heart is as follows:

1. SA node (Sinoatrial node)
2. Internodal pathways
3. AV node (Atrioventricular node)
4. AV bundle (Atrioventricular bundle or bundle of His)
5. Bundle branches (Right and Left bundle branches)
6. Purkinje fibers

The SA node initiates the electrical impulse, which then travels through the atria. After that, it reaches the AV node where there is a brief delay. This delay is crucial as it allows the atria to complete the contraction and pump blood into the ventricles. Following the delay, the impulse moves down the AV bundle, divides into the bundle branches within the interventricular septum, and finally spreads through the Purkinje fibers from the apex of the heart upwards through the ventricular myocardium.

It is important to note that during systole the heart contracts to pump blood, and during diastole it is filled with blood. The correct sequence ensures the coordinated contraction of the atria first and then the ventricles, ensuring efficient pumping of blood.