The heart’s electrical system is a complex network of specialized cells and tissues that work together to coordinate the heartbeat. This intricate system ensures that the heart’s four chambers contract in a specific sequence, allowing for the efficient pumping of blood throughout the body.
The main components of the heart’s electrical system include:Sinoatrial node (SA node):
Also known as the heart’s natural pacemaker, the SA node is a group of specialized cells located in the upper right atrium of the heart. The SA node spontaneously generates electrical impulses that initiate each heartbeat. [Image of Sinoatrial node (SA node) of the heart]Atrioventricular node (AV node):
Located at the lower border of the right atrium, between the atria and ventricles, the AV node acts as a control center. It receives electrical impulses from the SA node and slows them down slightly before sending them to the ventricles. This brief delay allows the atria to contract and fill the ventricles with blood before they pump blood out to the body. [Image of Atrioventricular node (AV node) of the heart].Bundle of His:
The Bundle of His is a short bundle of specialized cardiac muscle fibers that originates from the AV node and descends down the center of the heart wall. It acts as an electrical highway, transmitting the electrical signal from the AV node to the ventricles.Bundle branches:
The Bundle of His divides into two branches: the right bundle branch and the left bundle branch. These branches carry the electrical signal to the muscles of the right and left ventricles, respectively.Purkinje fibers:
The bundle branches further divide into even thinner fibers called Purkinje fibers, which spread throughout the ventricles. These fibers deliver the electrical signal directly to the heart muscle cells, causing them to contract and pump blood out of the heart. [Image of Purkinje fibers of the heart]The Flow of Electricity
The electrical impulse originates in the SA node and travels through the heart in a precise sequence:- The SA node generates an electrical impulse, which spreads through the right and left atria, causing them to contract and squeeze blood into the ventricles.
- The electrical impulse reaches the AV node, where it is slowed down. This delay allows the atria to complete their contraction before the ventricles contract.
- The impulse travels rapidly down the Bundle of His and its branches, stimulating the Purkinje fibers.
- The Purkinje fibers transmit the electrical signal to the heart muscle cells in the ventricles, causing them to contract and pump blood out to the lungs and body.