That beat can be felt as an external pulse. The SA node generates an electric beat about 60 to 80 times a minute, and each should result in a heartbeat. The signal then passes through electric bundles in the ventricle walls to allow these chambers to contract, again in a coordinated way, and pump blood to the lungs and body. At the AV node, the electric signal waits for a very short time, usually one- to two-tenths of a second, to allow blood pumped from the atria to fill up the ventricles. This electric signal causes muscle cells in both atria to contract at once. This pacemaker function begins the electrical impulse, which follows pathways in the atrial walls, almost like wiring, to a junction box between the atrium and ventricle called the atrioventricular node ( AV node). The SA node is considered the "natural pacemaker" of the heart. There are special cells in the right atrium called the sinoatrial node (SA node) that generate the first electrical impulse, allowing the heart to beat in a coordinated way. The left ventricle is much thicker than the right because it needs to be strong enough to send blood to the entire body. The oxygen-rich blood returns to the left atrium where the small atrial beat pushes it to the left ventricle. The right ventricle pumps blood to the lungs to pick up oxygen and release carbon dioxide. The right side of the heart pumps blood to the lungs while the left side pumps it to the rest of the body.īlood from the body depleted of oxygen and containing carbon dioxide is collected in the right atrium and then pushed into the right ventricle with a small beat of the upper chamber of the heart. The upper chambers are the right and left atria (singular = atrium) while the lower chambers are the right and left ventricles. These cells act as an automatic pacemaker, starting the electric signal that spreads along the "wiring" within the heart muscle, allowing a coordinated squeeze so that the pump can function. The initial electrical impulse that begins the process of a heartbeat is generated by a group of cells located in the upper chamber of the heart, the atrium. The heart is a two-stage electric pump whose job it is to circulate blood through the body. Picture of the heart's electrical system. They are either fast, slow, irregular and persistent, or intermittent. These can include electrolyte abnormalities in the bloodstream, abnormal hormone levels (for example thyroid function that is too high or too low), and medication or drug ingestions.Īny abnormality of the electrical cycle within the heart that generates an abnormal beat, whether it is too fast, too slow, skipped, or irregular is considered dysrhythmia.ĭysrhythmias are usually classified as originating from above the AV node (supraventricular) or below, the ventricle.
The issue may also be due to influences on the conducting system from outside the heart. Cardiac dysrhythmia (dys = abnormal or faulty + rhythm) might be a better term.ĭysrhythmias may occur because of problems directly associated with the electrical "wiring," the SA node, the AV node, or the ventricular conducting system.
Heart rhythm disorders are often referred to as cardiac arrhythmias (cardiac = heart a = lack of) but this is technically incorrect since in most cases there is a heart rhythm, but it is abnormal. Depending upon the abnormality, the heart may begin to beat too fast, too slow, irregularly, or not at all.
When the heart's electrical system malfunctions, the normal rhythm of the heart can be affected. Picture of the great vessels of the heart.
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