Node, AV
AV node: The AV node (AV stands for atrioventricular) 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 (SA stands for sinoatrial) 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:

  • AV node — The AV node (AV stands for atrioventricular) 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… …   Medical dictionary

  • Node, sinus — The sinus 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 …   Medical dictionary

  • Node, SA — The SA node (SA stands for sinoatrial) 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… …   Medical dictionary

  • Node, sinoatrial — The sinoatrial 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 …   Medical dictionary

  • AV (atrioventricular) — AV is the standard medical abbreviation for atrioventricular, a combination that means pertaining to the atria (the upper chambers of the heart) and the ventricles (the lower chambers of the heart). For example, the AV node is an electrical relay …   Medical dictionary

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  • 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 …   Medical dictionary

  • 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

  • AV node — atrioventricular node …   The new mediacal dictionary

  • First degree AV block — Infobox Disease Name = First degree AV block Caption = DiseasesDB = 10477 ICD10 = ICD10|I|44|0|i|30 ICD9 = ICD9|426.11 ICDO = OMIM = MedlinePlus = eMedicineSubj = emerg eMedicineTopic = 233 MeshID = First degree AV block or PR prolongation is a… …   Wikipedia

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