Sinus Rhythm - Cardiac Conduction System and Pathway

Cardiac Conduction System and Pathway

The cardiac conduction system is a pathway that consists of specialized cells, known as myocytes (cardiac cells), which create the natural electrical impulse that informs the heart when it needs to pump. The location within the conduction system that gives rise to electrical impulses is known as the pacemaker. The initial impulse originates in the sinoatrial (SA) node, or sinus node, which is located in the upper right atrium of the heart. The SA node is designated as the pacemaker of the heart. From the SA node, the electrical impulse spreads through interatrial tracts that spread the electrical impulse through the right and left atria and therefore cause atrial depolarization. As a result, a P-wave is observed. After the atria depolarize, the electrical impulse spreads through the internodal tracts and reach the atrioventricular node (AV node). The AV node has its own pacing rhythm that serves as a back up pacemaker in case the SA node fails to initiate an electrical impulse. Consequently, the AV node slows down the electrical impulse to allow the atria to project their blood into the ventricles. From the AV node, the impulse travels through the bundle of His, which bifurcate into the left and right bundle branches. From the branches, the impulse travels through the Purkinje fibers and allows the electrical impulse to end in the ventricles to initiate ventricular depolarization. Consequently, a QRS complex is observed.