AV (atrioventricular) node is a mass of modified heart muscle situated in the lower middle part of the right atrium. It receives the impulse to contract from the SA node via the atria and transmits it through the atrioventricular bundles to the ventricles. AV node is called the pace setter. Here, the impulses are delayed for 0.1 second to ensure that the auricles will contract first and empty fully before the ventricles contract.

The Pacemaker of the Heart: AV Node

The pacemaker of the heart is responsible for initiating and regulating the electrical impulses that control the heart's rhythm. It determines the rate at which the heart contracts and coordinates the sequence of contractions between the atria and ventricles. The pacemaker cells are specialized cardiac muscle cells that have the unique ability to generate and conduct electrical signals.

Function of the Pacemaker

The pacemaker sets the pace for the entire heart by generating electrical impulses. These impulses are then transmitted throughout the heart, causing the contraction of the cardiac muscle cells and ultimately leading to the pumping of blood. The pacemaker ensures that the heart beats in a coordinated and efficient manner.

Location of the Pacemaker

The main pacemaker of the heart is the sinoatrial (SA) node, located in the upper part of the right atrium. The SA node is often referred to as the natural pacemaker of the heart because it normally sets the rhythm for the entire heart. It generates electrical impulses at a regular rate, typically around 60-100 times per minute in a healthy adult.

Role of the AV Node

While the SA node is the primary pacemaker, there is a secondary pacemaker known as the atrioventricular (AV) node. The AV node is located in the lower part of the right atrium, near the septum. Its function is to relay the electrical impulses generated by the SA node to the ventricles.

Importance of the AV Node

The AV node acts as a delay mechanism, allowing the atria to contract and fill the ventricles with blood before the ventricles contract. This delay is essential for efficient blood flow and ensures that the atria and ventricles are in sync. Without this delay, the atria and ventricles would contract simultaneously, leading to ineffective pumping of blood.

Other Components of the Cardiac Conduction System

In addition to the SA node and AV node, there are other specialized conducting tissues in the heart that help transmit the electrical impulses to the ventricles. These include the bundle of His, bundle branches, and Purkinje fibers. While these components play a vital role in the conduction of electrical signals, the AV node is specifically responsible for relaying the impulses from the atria to the ventricles.

In conclusion, the pacemaker in the heart is primarily controlled by the SA node, which sets the rhythm for the entire heart. The AV node acts as a relay, ensuring a coordinated sequence of contractions between the atria and ventricles. Together, these components of the cardiac conduction system regulate the heart's electrical activity and ensure the efficient pumping of blood.