- 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.
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 rhythm — is a term used in medicine to describe the normal beating of the heart, as measured by an electrocardiogram (ECG). It has certain generic features that serve as hallmarks for comparison with normal ECGs. ECG Structure There are typically five… … Wikipedia
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 — 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
Sinus node — 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 — 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
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
Sinus arrhythmia — The normal increase in heart rate that occurs during inspiration (when you breathe in). This is a natural response and is more accentuated in children than adults. The sinus refers to the natural pacemaker of the heart which is called the… … Medical dictionary
Sinus bradycardia — SignSymptom infobox Name = Sinus bradycardia ICD10 = ICD9 = ICD9|427.81 MeshID = D001146 Sinus bradycardia is a heart rhythm that originates from the sinus node and has a rate of under 60bpm.Etiology*This rhythm may be caused by one of the… … Wikipedia