CARDIAC CONDUCTION SYSTEM

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 CARDIAC CONDUCTION SYSTEM

Step 1: Pacemaker Impulse Generation
The first step of cardiac conduction is impulse generation. The sinoatrial (SA) node (also referred to as the pacemaker of the heart) contracts, generating nerve impulses that travel throughout the heart wall. This causes both atria to contract. The SA node is located in the upper wall of the right atrium. It is composed of nodal tissue that has characteristics of both muscle and nervous tissue.
Step 2: AV Node Impulse Conduction
The atrioventricular (AV) node lies on the right side of the partition that divides the atria, near the bottom of the right atrium. When the impulses from the SA node reach the AV node, they are delayed for about a tenth of a second. This delay allows atria to contract and empty their contents into the ventricles prior to ventricle contraction.
Step 3: AV Bundle Impulse Conduction
The impulses are then sent down the atrioventricular bundle. This bundle of fibers branches off into two bundles and the impulses are carried down the center of the heart to the left and right ventricles.
Step 4: Purkinje Fibers Impulse Conduction
At the base of the heart, the atrioventricular bundles start to divide further into Purkinje fibers. When the impulses reach these fibers they trigger the muscle fibers in the ventricles to contract. The right ventricle sends blood to the lungs via the pulmonary artery. The left ventricle pumps blood to the aorta.


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