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The conduction system of the heart is a specialized network of cells responsible for generating and transmitting electrical impulses that control the heart's rhythmic contractions.
This system ensures that the heart beats in a coordinated and efficient manner to pump blood throughout the body.
The main elements of the conduction system include the sinoatrial (SA) node, atrioventricular (AV) node, bundle of His, bundle branches, and Purkinje fibers.
1. Sinoatrial (SA) node:
The SA node is a group of specialized cells located in the upper right atrium. It is often referred to as the natural pacemaker of the heart because it generates the electrical impulses that initiate each heartbeat.
The SA node fires electrical impulses at regular intervals, causing the atria to contract and pump blood into the ventricles.
2. Atrioventricular (AV) node:
The AV node is located in the lower part of the right atrium, near the tricuspid valve. It serves as a relay station, receiving impulses from the SA node.
The AV node briefly delays the electrical signal to allow the atria to finish contracting and the ventricles to fill with blood before they contract.
3. Bundle of His:
The bundle of His (atrioventricular bundle) is a group of specialized fibers that originates at the AV node and extends through the fibrous ring separating the atria and ventricles, then divides into the left and right bundle branches.
It transmits the electrical impulse from the AV node to the bundle branches.
4. Bundle branches:
The bundle branches are two sets of fibers that run along the interventricular septum (the wall that separates the left and right ventricles).
The left bundle branch further divides into the left anterior fascicle and the left posterior fascicle.
These branches carry the electrical impulse to the Purkinje fibers in the left and right ventricles.
5. Purkinje fibers:
Purkinje fibers are specialized cells that spread out through the ventricular myocardium (the heart muscle).
They rapidly conduct the electrical impulses, causing the ventricles to contract simultaneously and pump blood to the lungs (right ventricle) and the rest of the body (left ventricle).
Heartbeat
The heartbeat is a result of the electrical activity generated by the conduction system, which causes the heart muscle to contract.
A normal heartbeat consists of the following phases:
1. Atrial contraction:
The SA node fires an electrical impulse, causing the atria to contract and pump blood into the ventricles.
2. Ventricular contraction:
The electrical impulse travels through the AV node, bundle of His, bundle of his branches, and Purkinje fibers, causing the ventricles to contract and pump blood out of the heart.
3. Relaxation:
The electrical activity subsides, allowing the heart muscle to relax. The atria and ventricles refill with blood, preparing for the next heartbeat.
This sequence of events is known as the cardiac cycle, and it repeats continuously to maintain blood circulation throughout the body.
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