The Heart's Electrical System: Controlling Heart Contractions

Introduction

The heart's electrical system, also known as the cardiac conduction system, is responsible for controlling the heart's contractions and maintaining a regular heartbeat. It consists of a network of specialised cells that generate and transmit electrical impulses, enabling the heart muscle to contract and pump blood throughout the body.

Sinoatrial Node (SA Node)

The Heart's Natural Pacemaker

The sinoatrial node, located in the upper wall of the right atrium, is a small group of specialised cells. It generates electrical impulses that initiate each heartbeat. These impulses spread across both atria, causing them to contract and push blood into the ventricles.

Atrioventricular Node (AV Node)

The Relay Station

The atrioventricular node, situated near the tricuspid valve in the lower wall of the right atrium, acts as a relay station. It receives electrical impulses from the SA node and slows them down before transmitting them to the ventricles. This delay allows the atria enough time to contract and empty their blood into the ventricles before they contract.

Bundle of His and Bundle Branches

Transmitting Electrical Impulses to the Ventricles

The bundle of His, also known as the atrioventricular bundle, is a bundle of specialised fibres located in the septum, the heart's middle muscular wall that separates the right and left sides of the heart. It transmits electrical impulses from the AV node to the ventricles.

The bundle of His branches into the left and right bundle branches, which further transmit electrical impulses down the septum. The left bundle branch splits into the left anterior and left posterior fascicles, responsible for conducting the impulses to the left ventricle. The right bundle branch carries the impulses to the right ventricle.

Purkinje Fibers

Rapid Distribution of Electrical Impulses

The Purkinje fibres form a network of specialised fibres that originate from the bundle branches and spread through the ventricular myocardium. These fibres rapidly distribute the electrical impulses to the ventricular muscle cells, causing the ventricles to contract simultaneously and pump blood to the lungs and the rest of the body.

Conclusion

In conclusion, the heart's electrical system is a complex and coordinated network of specialised cells and fibres. Working together, they generate and transmit electrical impulses, ensuring the heart maintains a regular and efficient heartbeat. This vital system allows the heart to effectively pump blood throughout the body, supporting life and overall health.