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The sinoAtrial node (abbreviated SA node or SAN, also called the sinus node) is the impulse generating (pacemaker) tissue located in the right atrium of the heart, and thus the generator of sinus rhythm. It is a group of cells positioned on the wall of the right atrium, near the entrance of the superior vena cava. These cells are modified cardiac myocytes. They possess some contractile filaments, though they do not contract. Image File history File links Gray493. ...
The heart and lungs, from an older edition of Grays Anatomy. ...
In the development of the human heart, the right horn and transverse portion of the sinus venosus ultimately become incorporated with and form a part of the adult right atrium. ...
Image File history File links Gray501. ...
For other uses, see Latin (disambiguation). ...
Section of an artery For other uses, see Artery (disambiguation). ...
The sinuatrial nodal artery is an artery of the heart which supplies the sinoatrial node, and usually arises from either the right coronary artery or (less frequently) the circumflex branch of left coronary artery. ...
Medical Subject Headings (MeSH) is a huge controlled vocabulary (or metadata system) for the purpose of indexing journal articles and books in the life sciences. ...
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This page is about the muscular organ, the Heart. ...
The heart and lungs, from an older edition of Grays Anatomy. ...
Sinus rhythm is indicative of normal electrical conductance of the heart. ...
Superior vena cava - Wikipedia, the free encyclopedia /**/ @import /skins-1. ...
Myocyte is the technical term for a muscle cell. ...
Role as a pacemaker Although all of the heart's cells possess the ability to generate the electrical impulses (or action potentials) that trigger cardiac contraction, the sinoatrial node is what normally initiates it, simply because it generates impulses slightly faster than the other areas with pacemaker potential. Because cardiac myocytes, like all muscle cells, have refractory periods following contraction during which additional contractions cannot be triggered, their pacemaker potential is overridden by the sinoatrial node. In the heart, the pacemaker potential is the voltage created by impulses from an artificial electronic pacemaker or the SA node which drives the rhythmic firing of the heart. ...
Myocyte is the technical term for a muscle cell. ...
A top-down view of skeletal muscle Muscle (from Latin musculus little mouse [1]) is contractile tissue of the body and is derived from the mesodermal layer of embryonic germ cells. ...
It has been suggested that this article or section be merged into Refractory period. ...
Cells in the SA node will naturally discharge (create action potentials) at about 60-100 times/minute.[1] Because the sinoatrial node is responsible for the rest of the heart's electrical activity, it is sometimes called the primary pacemaker. Schematic of an electrophysiological recording of an action potential showing the various phases which occur as the wave passes a point on a cell membrane. ...
If the SA node does not function, or the impulse generated in the SA node is blocked before it travels down the electrical conduction system, a group of cells further down the heart will become the heart's pacemaker. These cells form the atrioventricular node (AV node), which is an area between the atria and ventricles, within the atrial septum. The atrioventricular node (abbreviated AV node) is an area of specialized tissue between the atria and the ventricles of the heart, which conducts the normal electrical impulse from the atria to the ventricles. ...
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. ...
The interatrial septum is the wall of tissue that separates the right and left atria of the heart. ...
Innervation The SA node is richly innervated by parasympathetic nervous system fibers (CN X: Vagus Nerve) and by sympathetic nervous system fibers (T1-4, Spinal Nerves). This makes the SA node susceptible to autonomic influences. Autonomic nervous system innervation, showing the sympathetic and parasympathetic (craniosacral) systems, in red and blue, respectively The parasympathetic nervous system is one of three divisions of the autonomic nervous system. ...
The vagus nerve (also called pneumogastric nerve or cranial nerve X) is the tenth of twelve paired cranial nerves, and is the only nerve that starts in the brainstem (within the medulla oblongata) and extends, through the jugular foramen, down below the head, to the abdomen. ...
The Sympathetic Nervous System (SNS) is a branch of the autonomic nervous system. ...
The term spinal nerve generally refers to the mixed spinal nerve, which is formed from the dorsal and ventral roots that come out of the spinal cord. ...
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- Stimulation of the vagus nerve (parasympathetic fibers) causes a decrease in the SA node rate (thereby decreasing the heart rate and force of contraction).
- Stimulation via sympathetic fibers causes an increase in the SA node rate (thereby increasing the heart rate and force of contraction).
Blood supply In the majority of patients, the SA node receives blood from the right coronary artery, meaning that a myocardial infarction occluding it will cause ischaemia in the SA node unless there is a sufficiently good anastomosis from the left coronary artery. If not, death of the affected cells will stop the SA node from triggering the heartbeat. The coronary circulation consists of the blood vessels that supply blood to, and remove blood from, the heart. ...
Acute myocardial infarction (AMI or MI), more commonly known as a heart attack, is a disease state that occurs when the blood supply to a part of the heart is interrupted. ...
In medicine, ischemia (Greek ισχαιμία, isch- is restriction, hema or haema is blood) is a restriction in blood supply, generally due to factors in the blood vessels, with resultant damage or dysfunction of tissue. ...
// Anastomosis (plural anastomoses) refers to a form of network in which streams both branch out and reconnect. ...
See also Cardiology is the branch of medicine pertaining to the heart. ...
The contractions of the heart are controlled by electrical impulses, these fire at a rate which controls the beat of the heart. ...
The normal electrical conduction in the heart allows the impulse that is generated by the sinoatrial node (SA node) of the heart to be propagated to (and stimulate) the myocardium (Cardiac muscle). ...
References - ^ http://sprojects.mmi.mcgill.ca/cardiophysio/AnatomySAnode.htm
External link | Anatomy of torso, cardiovascular system: heart | | Structures | atria (interatrial septum, musculi pectinati) • ventricles (interventricular septum, trabeculae carneae, chordae tendinae, papillary muscle) • valves • cusps | | Regions | base • apex • grooves (coronary/atrioventricular, interatrial, anterior interventricula, posterior interventricular) • surfaces (sternocostal, diaphragmatic) • borders (right, left) | | Right heart | (vena cavae, coronary sinus) → right atrium (auricle, fossa ovalis, limbus of fossa ovalis, crista terminalis, valve of the inferior vena cava, valve of the coronary sinus) → tricuspid valve → right ventricle (conus arteriosus, moderator band/septomarginal trabecula) → pulmonary valve → (pulmonary artery and pulmonary circulation) | | Left heart | (pulmonary veins) → left atrium (auricle) → mitral valve → left ventricle → aortic valve (aortic sinus) → (aorta and systemic circulation) | | Layers | pericardium: fibrous pericardium • serous pericardium (pericardial cavity, epicardium/visceral layer) • pericardial sinus
myocardium • endocardium • cardiac skeleton (fibrous trigone, fibrous rings) | | Conduction system | Cardiac pacemaker • SA node • AV node• bundle of His • Purkinje fibers | |
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