Medical Surgical Cardiac Fundamentals #2

Question

Which part of the electrical conduction system of the heart is considered the “pacemaker” of the heart?

Answers

  1. Bundle of His
    • Rationale:

      This answer is not correct because the Bundle of His is an extension of the AV node and its function is to transmit the heart’s electrical impulse between the AV node to the Purkinje fibers in the ventricles. This electrical signal results in a synchronized contraction of the ventricles.

  2. Purkinje fibers
    • Rationale:

      This answer is not correct because Purkinje fibers electrically conduct impulses to the ventricular muscle. This happens at the end of the conduction path, whereas the sinoatrial (SA) node is at the start for the point of the pathway (paces) and therefore is called the “pacemaker”.

  3. Sinoatrial node
    • Rationale:

      This answer is correct because the sinoatrial (SA) node is considered the natural “pacemaker” of the heart. It is a cluster of cells that is located in the upper part of the posterior wall of the right atrium, which is the upper chamber of the heart. The cells of the SA node have the ability to naturally produce an electrical signal and are the start for the point of pathway, hence its nickname, “pacemaker.”

  4. Atrioventricular node
    • Rationale:

      This answer is not correct because the atrioventricular node is the part of the electrical conduction system just after the SA node. Its job is to coordinate the top part of the heart (the atria) with the bottom part of the heart (the ventricles).

Overview

The sinoatrial (SA) node is considered the natural “pacemaker” of the heart.

Explanation

Learning Outcomes

The sinoatrial (SA) node is the body’s natural pacemaker. It is a cluster of cells that is located in the upper part of the posterior wall of the right atrium, which is the upper chamber of the heart. The cells of the SA node have the ability to naturally produce an electrical signal. The heart’s normal electrical signal flows in a certain pattern: Sinoatrial (SA) node, atrioventricular (AV) node, Bundle of His, right and left bundle branches, Purkinje fibers. A disruption of this signal flow produces EKG changes, blocks, and dysrhythmias. Understanding this signal flow is imperative to understanding the fundamentals of the electrical flow of the heart.

Test Taking Tip

The pacemaker is the initiator of the impulse. If you can remember this silly saying: “SAAV HIS bundle of PJs”, you can see that the SA node is first of the electrical conduction system and the heart’s pacemaker!

Video Rationale