Node, atrioventricular
The atrioventricular (AV) node is an electrical relay station between the atria (the upper) and the ventricles (the lower chambers of the heart). Electrical signals from the atria must pass through the AV node to reach the ventricles. The AV node is one of the major elements in the cardiac conduction system, the system that controls the heart rate. This stunningly designed system generates electrical impulses and conducts them throughout the muscle of the heart, stimulating the heart to contract and pump blood. The SA node The SA, or sinoatrial, node is the heart's natural pacemaker. The SA node consists of a cluster of cells that are situated in the upper part of the wall of the right atrium (the right upper chamber of the heart). The electrical impulses are generated there. The SA node is also called the sinus node. The electrical signal generated by the SA node moves from cell to cell down through the heart until it reaches the AV node, a cluster of cells situated in the center of the heart between the atria and ventricles. The AV node serves as a gate (an "electrical relay station") that slows the electrical current before the signal is permitted to pass down through to the ventricles. This delay ensures that the atria have a chance to fully contract before the ventricles are stimulated. After passing the AV node, the electrical current travels to the ventricles along special fibers embedded in the walls of the lower part of the heart. The autonomic nervous system, the same part of the nervous system as controls the blood pressure, controls the firing of the SA node to trigger the start of the cardiac cycle. The autonomic nervous system can transmit a message quickly to the SA node so it in turn can increase the heart rate to twice normal within only 3 to 5 seconds. This quick response is important during exercise when the heart has to increase its beating speed to keep up with the body's increased demand for oxygen.

Medical dictionary. 2011.

Look at other dictionaries:

  • atrioventricular bundle — n BUNDLE OF HIS * * * (AV bundle, bundle of His) a bundle of modified heart muscle fibres (Purkinje fibres) passing from the atrioventricular node forward to the septum between the ventricles, where it divides into right and left bundles, one for …   Medical dictionary

  • Atrioventricular — (having to do with an atrium and ventricle) can refer to: *Left atrioventricular opening *Atrioventricular fistula *Atrioventricular node *The term Atrioventricular valves is used to describe the mitral valve and tricuspid valve …   Wikipedia

  • Node — Literally a knot, a node is a collection of tissue. For example a lymph node, is a collection of lymphoid tissue. A nodule is a small node, a little collection of tissue. * * * 1. A knob or nodosity; a circumscribed swelling; in anatomy, a… …   Medical dictionary

  • atrioventricular node — noun a node of specialized heart muscle located in the septal wall of the right atrium; receives impulses from the sinoatrial node and transmits them to atrioventricular bundle • Hypernyms: ↑cardiac muscle, ↑heart muscle * * * noun : a small mass …   Useful english dictionary

  • Atrioventricular node — The atrioventricular (AV) node is an electrical relay station between the atria (the upper) and the ventricles (the lower chambers of the heart). Electrical signals from the atria must pass through the AV node to reach the ventricles. The AV node …   Medical dictionary

  • Atrioventricular node — Infobox Anatomy Name = PAGENAME Latin = nodus atrioventricularis GraySubject = GrayPage = Caption = AV node visible near bend of red line. Caption2 = Heart; conduction system Precursor = System = Artery = atrioventricular nodal branch Vein =… …   Wikipedia

  • atrioventricular bundle — noun a bundle of modified heart muscle that transmits the cardiac impulse from the atrioventricular node to the ventricles causing them to contract • Syn: ↑bundle of His, ↑atrioventricular trunk, ↑truncus atrioventricularis • Hypernyms: ↑cardiac… …   Useful english dictionary

  • atrioventricular node — Anat. a small mass of muscular fibers at the base of the wall between the atria, conducting impulses received from the sinoatrial node by way of the atrioventricular bundles and, under certain conditions, functioning for the sinoatrial node as… …   Universalium

  • atrioventricular node — AV node a mass of modified heart muscle situated in the lower middle part of the right atrium. It receives the impulse to contract from the sinoatrial node, via the atria, and transmits it through the atrioventricular bundle to the ventricles …   The new mediacal dictionary

  • Atrioventricular nodal branch — Infobox Artery Name = Atrioventricular nodal branch Latin = ramus nodi atrioventricularis GraySubject = GrayPage = Caption = Sternocostal surface of heart. Caption2 = ARTERIES: RCA = right coronary AB = atrial branches SANB = sinuatrial nodal RMA …   Wikipedia

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