Elements of the Conduction System of the Heart and the Heartbeat

Conduction system of heart

• The conduction system of the Heart and the Heartbeat 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 include the sinoatrial (SA) node, atrioventricular (AV) node, bundle of His, bundle branches, and Purkinje fibers.

Conduction system of heart

1. Sinoatrial (SA) Node

• The SA node is located in the upper right atrium and is often called the natural pacemaker of the heart.

• It generates electrical impulses at regular intervals, initiating each heartbeat and 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 acts as a relay station, receiving electrical impulses from the SA node.

• The AV node delays the electrical signal briefly, allowing the atria to complete contraction 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.

• It extends through the fibrous ring separating the atria and ventricles and divides into the left and right bundle branches.

• The bundle of His transmits the electrical impulse from the AV node to the bundle branches.

4. Bundle Branches

• The bundle branches consist of two sets of fibers running along the interventricular septum (the wall between the left and right ventricles).

• The left bundle branch divides further into the left anterior fascicle and left posterior fascicle.

• These branches carry the electrical impulse to the Purkinje fibers in both ventricles.

5. Purkinje Fibers

• Purkinje fibers are specialized cells that spread throughout the ventricular myocardium (heart muscle).

• They rapidly conduct the electrical impulses, causing both ventricles to contract simultaneously, pumping blood to the lungs (right ventricle) and the rest of the body (left ventricle).

Heartbeat

• The heartbeat is the result of electrical activity generated by the heart's conduction system, which causes the heart muscles to contract.

• A normal heartbeat consists of the following phases, forming a sequence known as the cardiac cycle.

Phases of the Heartbeat:

1. Atrial Contraction

• The SA node fires an electrical impulse, causing the atria to contract.

• This contraction pumps blood from the atria into the ventricles.

2. Ventricular Contraction

• The electrical impulse travels through the AV node, Bundle of His, bundle branches, and Purkinje fibers.

• This causes the ventricles to contract and pump blood out of the heart—blood is sent to the lungs from the right ventricle and to the rest of the body from the left ventricle.

3. Relaxation

• After the electrical activity subsides, the heart muscle relaxes.

• During this phase, both the atria and ventricles refill with blood, preparing for the next heartbeat.