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 the heart to contract and pump blood. Also abbreviated, SA node. The SA 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 atrioventricular node (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 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.

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  • 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

  • node — n. a small swelling or knot of tissue. See: atrioventricular node, lymph node, sinoatrial node …   The new mediacal dictionary

  • sinoatrial — adjective Etymology: New Latin sinus + atrium Date: 1913 of, involving, or being the sinus node < sinoatrial block > …   New Collegiate Dictionary

  • Sinoatrial arrest — or sinus arrest is a medical condition wherin the sinoatrial node of the heart transiently ceases to generate the electrical impulses that normally stimulate the myocardial tissues to contract and thus the heart to beat. Since the heart contains… …   Wikipedia

  • sinoatrial node — [sī΄nōô rik′yə lərsī΄nō ā′trē əl] n. PACEMAKER (sense 2a): sometimes called sinoauricular node [sī΄nōô rik′yə lər] …   English World dictionary

  • sinoatrial block — sinoatrial exit block a disturbance in which the atrial response is delayed or omitted because of partial or complete interference with the propagation of impulses from the sinoatrial node to the atria …   Medical dictionary

  • Sinoatrial node — Infobox Anatomy Name = Sinoatrial or (el) node Latin = nodus sinuatrialis GraySubject = GrayPage = Caption = Interior of right side of heart. (SA node not labeled, but region visible at left, near crista terminalis. Caption2 = Schematic… …   Wikipedia

  • Sinoatrial node — The sinoatrial node (the SA 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 …   Medical dictionary

  • Sinoatrial block — Infobox Disease Name = PAGENAME Caption = DiseasesDB = ICD10 = ICD10|I|45|5|i|30 ICD9 = ICD9|426.6 ICDO = OMIM = MedlinePlus = eMedicineSubj = eMedicineTopic = MeshID = D012848 A sinoatrial block is a type of heart block which involves an… …   Wikipedia

  • 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

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