- 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 sinus node to trigger the start of the cardiac cycle. The autonomic nervous system can transmit a message quickly to the sinus 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.
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Medical dictionary. 2011.
Look at other dictionaries:
sinus node — noun : sinoatrial node * * * /suy neuhs/, Anat. See sinoatrial node. * * * sinus node, = sinoatrial node. (Cf. ↑sinoatrial node) … Useful english dictionary
sinus node — /suy neuhs/, Anat. See sinoatrial node. * * * … Universalium
sinus node — noun Date: 1937 a small mass of tissue that is embedded in the musculature of the right atrium of higher vertebrates and that originates the impulses stimulating the heartbeat … New Collegiate Dictionary
sinus node — /ˈsaɪnəs noʊd/ (say suynuhs nohd) noun a dense network of specialised conduction fibres at the junction of the superior vena cava and the right atrium; normally originates the cardiac rhythm and has been called the pacemaker of the heart … Australian English dictionary
sinus node reentrant tachycardia — sinus node reentry tachycardia, sinus reentrant tachycardia tachycardia arising from a reentrant circuit that encompasses the sinus node … Medical dictionary
sinus node electrogram — an intracardiac electrogram obtained by placing electrodes near the sinus node; it is used in examining the time for impulse conduction from the node to the atrium … Medical dictionary
Sinus — may refer to:In anatomy, where a sinus is a sac or cavity in any organ or tissue: *Sinus (anatomy), description of the general term *Anal sinuses, the furrows which separate the columns in the rectum *Paranasal sinuses, air cavities in the… … Wikipedia
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
Sinus rhythm — The normal regular rhythm of the heart set by the natural pacemaker of the heart called the sinoatrial (or sinus) node. It is located in the wall of the right atrium (the right upper chamber of the heart). Normal cardiac impulses start there and… … Medical dictionary
Sinus tachycardia — A fast heartbeat (tachycardia) because of rapid firing of the sinoatrial (sinus) node. The sinoatrial (or sinus) node is the natural pacemaker of the heart. It is located in the wall of the right atrium (the right upper chamber of the heart).… … Medical dictionary