Cardiac Conduction System

March 26, 2009. The heart doe not have neurons(nerve tissue). The heart’s beating is from specialized cardiac muscle fibers that are the source of the electrical activity. These muscle fibers are called autorhythmic cells and the act as a pacemaker setting the contraction rhythm for the entire heart. Cardiac conduction system begins at sinatorial node(SA) on the back wall of the right atrium. The action potential causes the atria to contract and travel to the atrioventricular node(AV). The AV node is located in the interatrial septum, anterior to the opening of the coronary sinus. From the AV node to action potential enters the bundle of His, this is the site where the action potential moves from the atria to the ventricles. The action potential enters both the right and left bundle branches and travels through the interventricular septum toward the apex. Purkinje fibers rapidly conduct the action potential to the apex of the ventricles. The ventricles contract pushing the blood up toward the semilunar valves. This SA node action potential happens about 100 times a minute. Na+(sodium) ions are used for conduction, the Na+ causes Ca+(calcium) ion channels to open. Ca+ ions drives contraction. The phase of contraction is referred to as systole, the relaxation phase is diastole. Blood pressure is systolic over the diastolic, the force exerted by circulating blood on the walls of the blood vessels.
Cardiac patients are seen often at the hospital. Some patients present with extreme high blood pressures where others present with extreme low BP’s. Vital signs are one of the duties I perform. Understanding the conduction system of the heart gives me more knowledge as to why a doctor would be concerned with a dramatic change in vital signs.