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Topic: Sinoatrial node

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SA node

Atrioventricular node

Purkinje fibers

First degree heart block

Electrical conduction system of the heart

Tachycardia

Cardiac arrhythmia

Bradycardia

Cardiology

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	Atrioventricular node - Wikipedia, the free encyclopedia
		The atrioventricular node (abbreviated AV node) is the tissue between the atria and the ventricles of the heart, which conducts the normal electrical impulse from the atria to the ventricles.
		This is the property of the AV node that prevents rapid conduction to the ventricle in cases of rapid atrial rhythms, such as atrial fibrillation or atrial flutter.
		The blood supply of the AV node is from a branch of the right coronary artery in 85 to 90 percent of individuals, and from a branch of the left circumflex artery in 10 to 15 percent of individuals.
	en.wikipedia.org /wiki/AV_node (241 words)

	University of Miami School of Medicine - Glossary - Sinoatrial node
		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.
		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 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.
	www.med.miami.edu /glossary/art.asp?articlekey=5495 (314 words)

	Sinoatrial node - Wikipedia, the free encyclopedia
		The sinoatrial node (abbreviated SA node, also called the sinus node) is the impulse generating (pacemaker) tissue located in the right atrium of the heart.
		The sinoatrial node (SA node) is a group of cells positioned on the wall of the right atrium, near the entrance of the superior vena cava.
		Because the sinoatrial node is responsible for the rest of the heart's electrical activity, it is sometimes called the primary pacemaker.
	en.wikipedia.org /wiki/Sinoatrial_node (390 words)

	Heart
		The rhythmic sequence of contractions is coordinated by the sinoatrial node and atrioventricular nodes.
		The sinoatrial node, often known as the cardiac pacemaker, is located in the upper wall of the right atrium and is responsible for the wave of electrical stimulation (See action potential) that initiates the atria to contract.
		The time taken for the wave to reach this node from the sinoatrial nerve creates a delay between contraction of the two chambers and ensures that each contraction is coordinated simultaneously throughout all of the heart.
	www.brainyencyclopedia.com /encyclopedia/h/he/heart.html (1255 words)

	Sinoatrial Node Dysfunction
		The normal pacemaker of the heart, termed the sinus (or sinoatrial (SA)) node, is responsible for generating the electrical impulse that triggers the heart to contract and pump blood.
		Most cases of sinus node dysfunction is the result of fixed damage to or degeneration of sinoatrial tissue and it is typically seen in the elderly or patients with significant structural heat disease, including coronary artery disease, congestive heart failure, or cardiomyopathy.
		In some cases, sinus node dysfunction may be secondary to, or worsened by, medications (see table 1 below) that the patient may be taking for control of other cardiovascular problems, including supraventricular tachyarrhythmias, ventricular tachyarrhythmias, hypertension (high blood pressure), coronary artery disease, or congestive heart failure.
	www.kpep.org /bradyarrhythmias/sinus_node_dysfunc.htm (470 words)

	Sinoatrial node -- Facts, Info, and Encyclopedia article (Site not responding. Last check: 2007-10-08)
		The sinoatrial node (abbreviated SA node, also called the sinus node) is the impulse generating (pacemaker) tissue located in the right atrium of the (The hollow muscular organ located behind the sternum and between the lungs; its rhythmic contractions pump blood through the body) heart.
		Although all of the hearts cells possess the ability to generate the electrical impulses (or action potentials) which trigger cardiac contraction, the sinoatrial node is what normally initiates it, simply because it generates impulses slightly faster than the other areas with (Click link for more info and facts about pacemaker potential) pacemaker potential.
		The SA node is richly innervated by (Click link for more info and facts about vagal) vagal and (Click link for more info and facts about sympathetic) sympathetic fibers.
	www.absoluteastronomy.com /encyclopedia/S/Si/Sinoatrial_node.htm (369 words)

	The Sinoatrial Node (Site not responding. Last check: 2007-10-08)
		The depolarization and repolarization of the SA node and the other elements of the heart's electical system produces a strong pattern of voltage change which can be measured with electrodes on the skin.
		The circuit involves a capacitor which is charged by the energy of a battery(roles played by the membranes of the SA node and the ion transport processes which repolarize it) and a resistor which controls the rate of flashing of the light.
		In the case of the SA node, there is input frorm the physiology of the body related to oxygen demand and other factors which control the rate of firing of the SA node and therefore the heartrate.
	hyperphysics.phy-astr.gsu.edu /hbase/biology/sanode.html (278 words)

	Conduction System
		The atrioventricular node is oval in shape and a little smaller than the sinoatrial node.
		Because of this arrangement, the impulses dispatched from the atrioventricular node first activate ventricular muscle in the region of the apex, assuring a "milking" action of the ventricles toward the openings of the aorta and the pulmonary trunk.
		The potential of the sinoatrial node fibers between discharges has a negativity o fonly -55 to -60 millivolts in comparison with a ventricular muscle fiber which depolarizes at -85 to -90 millivolts.
	oak.cats.ohiou.edu /~jr888793/conduction.html (1724 words)

	Biomedical Sciences (Site not responding. Last check: 2007-10-08)
		The sinoatrial node is a non-uniform tissue in terms of its structure, electrophysiology and function.
		We are mapping the sinoatrial node by studying the electrical activity of single sinoatrial node cells from different regions of the node and by the use of immunocytochemistry to measure the distribution of various ion channels in the different regions of the node.
		With age the pacemaker of the heart, the sinoatrial node, deteriorates and in some cases the deterioration necessitates the fittting of an artificial pacemaker.
	www.leeds.ac.uk /bms/staff/mrb (877 words)

	oehmen
		In the rabbit sinoatrial node, endogenous pacing activity is responsible for initiating the propagating wave of depolarization which ultimately causes contraction of each heart chamber.
		Since the bidomain model assumes a cable-type configuration of cells and omits single-cell properties which may dramatically impact pacing behavior, it is not appropriate to apply bidomain models to three-dimensional models of the sinoatrial node tissue.
		The sinoatrial node is of primary importance in understanding arrhythmias of many types because it is the originator of cardiac conduction, and therefore, contraction.
	www.krellinst.org /Fellows/oehmen.html (237 words)

	sinoatrial node (anatomy) - General Practice Notebook (Site not responding. Last check: 2007-10-08)
		The sinuatrial node of the heart is the first component of the conducting system of the heart.
		The artery of the sinuatrial node traverses the node; it is purported that it may serve a physiological function by conveying aortic pressure to nodal tissue.
		The wave of depolarisation of the sinuatrial node passes to the atrioventricular node by either direct conduction through the atria, conduction through specialised internodal pathways, or a combination of both routes.
	www.gpnotebook.co.uk /medwebpage.cfm?ID=1436155964 (1025 words)

	The Cardiac Cycle
		The specialised cardiac muscle of the SA node is characterised by the property of automatic self-excitation and it initiates each beat of the heart.
		Therefore, the SA node is often referred to as the pacemaker of the heart.
		Since the fibres of the SA node fuse with the surrounding atrial muscle fibres, the action potential generated in the nodal tissue spreads throughout both atria at a rate of approximately 0.3 meter per second and produces atrial contraction.
	www.jdaross.cwc.net /cardiac_cycle.htm (1160 words)

	Gradient Model Versus Mosaic Model of the Sinoatrial Node - Zhang (ResearchIndex) (Site not responding. Last check: 2007-10-08)
		3 The SA node is heterogeneous, and electrical activity changes from the periphery to the center in a characteristic...
		2 Pacemaker activity of the rabbit sinoatrial node: a comparis..
		1 The mammalian sinoatrial node (context) - Opthof - 1988
	citeseer.ist.psu.edu /zhang01gradient.html (510 words)

	Heart Physiology
		The Sinoatrial Node (often called the SA node or sinus node) serves as the natural pacemaker for the heart.
		The impulse that originates from the sinoatrial node strikes the Atrioventricular node (or AV node) which is situated in the lower portion of the right atrium.
		The atrioventricular node in turn sends an impulse through the nerve network to the ventricles, initiating the same wave-like contraction of the ventricles.
	www.cardioconsult.com /Physiology (435 words)

	AnatomySAnode
		The sinoatrial node (SA node) consists of a cluster of specialized cells that have pacemaker activity (automaticity).
		The SA node is located high on the right atrium close to whether the superior vena cava enters the right atrium.
		The rhythm originates from the SA node because the SA node depolarizes more frequently (60-100 beats per minute) than the AV node (40-60 beats per minute) and ventricular conducting system (30-40 beats per minute) so the AV node and ventricular conducting system are 'captured' by the sinus impulse and driven at 60-100 beast per minute.
	sprojects.mmi.mcgill.ca /cardiophysio/AnatomySAnode.htm (376 words)

	Identifying Drug-Induced Changes in Electrocardiogram Results of Elderly Individuals
		The sinoatrial node, located at the junction of the superior vena cava and the right atrium, is the area of the heart which, under normal conditions, depolarizes most rapidly.
		Thus, the sinoatrial node is often referred to as the pacemaker of the heart.
		Once the wave of depolarization reaches the AV node, there is a delay that allows the atria to contract, thus emptying blood into the ventricles before the ventricles are stimulated to contract.
	www.ascp.com /public/pubs/tcp/1997/jan/idicerei.html (2640 words)

	Sinus node definition - Medical Dictionary definitions of popular medical terms
		The sinus 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 sinus node is also called the sinoatrial node or, for short, the SA node.
		The electrical signal generated by the sinus 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.
	www.medterms.com /script/main/art.asp?articlekey=8448 (458 words)

	ECGs AND PACEMAKERS (Site not responding. Last check: 2007-10-08)
		Normally, the conduction impulse originates from the sinoatrial node in the right atrium and rapidly travels along 3 internodal atrial conduction tracts between the sinoatrial node and the atrioventricular node (Figure 1).
		The atrioventricular node has 3 functions: (1) delay the conduction impulse, allowing the ventricles to relax and fill before contraction; (2) control the number and order of supraventricular impulses that can conduct to the ventricles; and (3) serve as a subsidiary pacemaker if the sinoatrial node fails.
		An increase in the rate of the sinoatrial node (eg, by exercise, atropine, or atrial pacing) may worsen type II block because the faster sinus rate increases the repolarization time of the conducting tissue and increases the number of P waves that cannot conduct to the ventricles.
	www.aacn.org /aacn/jrnlccn.nsf/c54ad59fdf5d6228882565a0006a1369/5fe2adbebe94952f882569f400056d54?OpenDocument (3938 words)

	Indian Pacing and Electrophysiology Journal - Simmers (Site not responding. Last check: 2007-10-08)
		Sequential microelectrode measurements of sinus node and atrial transmembrane potentials were performed in an attempt to provide a temporal and anatomical map of the observed phenomenon.
		The authors attributed this to sinoatrial reentry, and went on to describe each of the three responses to premature atrial beats in a 70-year-old man in an elegant electrocardiographic deduction of underlying mechanisms.
		Sinoatrial reentry tachycardia is a relatively uncommon arrhythmia in the literature, but may be prone to underdiagnosis due to electrocardiographic similarity to sinus tachycardia and misinterpretation of symptoms as psychosomatic.
	www.ipej.org /0303/simmers.htm (2834 words)

	[No title] (Site not responding. Last check: 2007-10-08)
		The sinoatrial node sends one electrical signal telling the atrium to contract and another signal to the AV node for relay to the ventricles.
		The SA node may be partially or totally destroyed via inflammatory and/or degenerative processes.
		The normal cycle of electrical stimulation of the heart that begins in the sinoatrial node (SA node), traveling to the left atrium and down to the AV node.
	sprojects.mmi.mcgill.ca /cardiophysio/glossary.asp?l=S (377 words)

	APStracts 5:0500H, 1998. (Site not responding. Last check: 2007-10-08)
		The electrophysiological properties of sinoatrial (SA) node pacemaker cells vary in different regions of the node.
		In this study, we have investigated variation of the 4-aminopyridine (4-AP)-sensitive current as a function of the size (as measured by the cell capacitance) of SA node cells to elucidate the ionic mechanisms.
		The 10 mM 4-AP-sensitive current recorded from rabbit SA node cells was composed of transient and sustained components (Itrans and Isus).
	www.uth.tmc.edu /apstracts/1998/heart/December/500H.html (256 words)

	School of Biomedical Sciences (Site not responding. Last check: 2007-10-08)
		Effect of ageing on the sinoatrial node, the pacemaker of the heart.
		The sinoatrial node (SAN) or pacemaker of the heart is a complex heterogeneous tissue, responsible for normal function of the healthy mammalian heart.
		Student vacation scholarship for James Tellez, entitled ‘Effect of ageing on the sinoatrial node, the pacemaker of the heart, by determination of protein expression of various ion channels’.
	www.leeds.ac.uk /bms/staff/saj/index.php (1314 words)

	Sarcoplasmic Reticulum Ca2+ Release Is Not a Dominating Factor in Sinoatrial Node Pacemaker Activity -- Honjo et al. 92 ...
		of ryanodine on the intact SA node of the rabbit.
		B, Mean percentage change in spontaneous rate (±SEM) on application of ryanodine and isoproterenol to the intact sinoatrial node and on application of ryanodine to isolated SA node cells.
		Boyett MR, Honjo H, Kodama I. The sinoatrial node, a heterogeneous pacemaker structure.
	circres.ahajournals.org /cgi/content/full/92/3/e41 (2253 words)

	Sinoatrial Node Dysfunction and Early Unexpected Death of Mice With a Defect of klotho Gene Expression -- Takeshita et ... (Site not responding. Last check: 2007-10-08)
		Sinoatrial Node Dysfunction and Early Unexpected Death of Mice With a Defect of klotho Gene Expression -- Takeshita et al.
		Sinoatrial node function in vivo estimated by pharmacological blockade of autonomic influence and overdrive suppression test.
		Sinoatrial node region of klotho-null mouse stained with X-gal and anti-Cx40 antibody.
	circ.ahajournals.org /cgi/content/full/109/14/1776 (3393 words)

	APStracts 5:0233H, 1998. (Site not responding. Last check: 2007-10-08)
		Effects were greater in tissue from the periphery of the node than from the centre.
		In the intact sinoatrial node, 4-AP resulted in a shift of the leading pacemaker site consistent with the regional differences in the response to 4-AP.
		It is concluded that 4 -AP-sensitive outward current plays a major role in action potential repolarization and pacemaker activity in the sinoatrial node and its role varies regionally.
	www.uth.tmc.edu /apstracts/1998/heart/June/233H.html (246 words)

	Cellml.org - Modelling The Effect Of Intracellular Ca2+ On Sinoatrial Node Action Potentials, 2001 (Site not responding. Last check: 2007-10-08)
		Zhang et al published a mathematical model which describes the action potentials in the periphery and center of the rabbit sinoatrial node.
		The SA node is functionally, anatomically and electrophysiologically heterogeneous.
		Control of the pacemaker activity of the sinoatrial node by intracellular Ca Experiments and modelling, M.R. Boyett, H. Zhang, A. Garny and A.V. Holden, 2001, Phil.
	www.cellml.org /examples/repository/B_SAN_model_2001_doc.html (485 words)

	Heart Health Nutrient - Nature's Essence (Site not responding. Last check: 2007-10-08)
		It promotes heart health by stimulating the sinoatrial node, enhancing cardiac muscle contraction, and improving blood supply to the cardiac muscle.
		This contraction is initiated by electrical impulses that start at the sinoatrial node and spread to other part of the cardiac muscle.
		Thus, the health of sinoatrial node, cardiac contraction and cardiac blood supply are essential to the heart health.
	www.organix.net /organix/hearthtm.htm (836 words)

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