Heart Conduction System: What To Know

The Heart's Conduction System: Coordinating Heartbeats

The heart's conduction system is an intricate network of specialized tissues and structures that regulate the heartbeat and ensure that the heart's chambers contract in a coordinated and synchronous manner. This system acts as the heart's internal electrical wiring, generating and transmitting electrical impulses that trigger heart muscle contractions.

Components of the Heart's Conduction System

1. Sinoatrial Node (SA Node):

- Location: Located in the right atrium, near the opening of the superior vena cava.

- Function: The SA node is the primary pacemaker of the heart. It generates electrical impulses that initiate each heartbeat. The SA node's inherent electrical properties cause it to discharge regularly, setting the heart's basic rhythm.

2. Atrioventricular Node (AV Node):

- Location: Situated at the junction of the atria and ventricles, between the atrial septum and the tricuspid valve.

- Function: The AV node acts as a gatekeeper, delaying the electrical signals from the SA node before they reach the ventricles. This delay ensures that the atria have sufficient time to fill with blood before ventricular contraction.

3. Bundle of His:

- Location: Originating from the AV node, the bundle of His divides into three branches: the left bundle branch, the right bundle branch, and the AV bundle (bundle of Kent).

- Function: The bundle of His conducts the electrical impulses from the AV node to the ventricles. The left and right bundle branches carry the signals to the left and right ventricles, respectively, causing their contractions.

4. Purkinje Fibers:

- Location: Purkinje fibers are specialized fibers connected to the bundle branches and spread throughout the ventricular myocardium.

- Function: Purkinje fibers rapidly transmit the electrical impulses from the bundle branches to all parts of the ventricles, ensuring synchronized ventricular contraction.

Cardiac Excitation Sequence:

The heart's conduction system coordinates the sequence of cardiac excitation:

1. The SA node generates an electrical impulse that spreads across both atria, causing atrial contraction (atrial systole).

2. The electrical signal reaches the AV node, where it is briefly delayed. This delay allows the atria to complete their contraction and fill the ventricles with blood.

3. The electrical impulse then travels down the bundle of His and along the bundle branches, reaching the Purkinje fibers.

4. The Purkinje fibers rapidly distribute the impulse throughout the ventricular myocardium, triggering ventricular contraction (ventricular systole).

This coordinated sequence ensures efficient pumping of blood from the heart to the body and maintains the rhythmic beating of the heart. Dysfunctions or abnormalities in the heart's conduction system can lead to various heart rhythm disorders (arrhythmias), which may require medical intervention or treatment.