| Sinuatrial or (el) node | |
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| Interior of right side of heart. The heart is a muscular organ in all Vertebrates responsible for pumping Blood through the Blood vessels by repeated rhythmic (SA node not labeled, but region visible at left, near crista terminalis. 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 | |
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| Schematic representation of the atrioventricular bundle of His. | |
| Latin | nodus sinuatrialis |
| Artery | sinuatrial nodal artery |
| MeSH | Sinoatrial+Node |
| Dorlands/Elsevier | n_09/12577255 |
The Sinuatrial 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. Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome. Arteries are Blood vessels that carry blood away from the Heart. The sinoatrial nodal artery is an Artery of the Heart which supplies the Sinoatrial node, and usually arises from either the Right coronary artery Medical Subject Headings ( MeSH) is a huge Controlled vocabulary (or metadata system for the purpose of indexing journal articles and books Elsevier, the world's largest Publisher of Medical and Scientific literature, forms part of the Reed Elsevier group The right atrium (in older texts termed the "right auricle" is one of four chambers (two atria and two ventricles in the Human The heart is a muscular organ in all Vertebrates responsible for pumping Blood through the Blood vessels by repeated rhythmic Sinus rhythm is a term used in medicine to describe the normal beating of the heart as measured by an Electrocardiogram ( ECG) It is a group of cells positioned on the wall of the right atrium, near the entrance of the superior vena cava. The superior vena cava is a large yet short Vein that carries deoxygenated Blood from the upper half of the body to the Heart 's Right atrium These cells are modified cardiac myocytes. A myocyte (also known as a myocardial cell is the type of cell found in heart muscles. Though they possess some contractile filaments, they do not contract.
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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. 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 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. A myocyte (also known as a myocardial cell is the type of cell found in heart muscles. Muscle (from Latin musculus, diminutive of mus "mouse" is contractile tissue of the body and is derived from the In Physiology, a refractory period is a period of time during which an organ or cell is incapable of repeating a particular action or (more precisely the amount of time
Cells in the SA node will naturally discharge (create action potentials) at about 60-100 times/minute. In Neurophysiology, the action potential is a self-regenerating Wave of Electrochemical activity that allows Nerve cells to carry a signal [1] Because the sinoatrial node is responsible for the rest of the heart's electrical activity, it is sometimes called the primary pacemaker.
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, specifically The atrioventricular node (abbreviated AV node) is an area of specialized tissue between the atria and the ventricles of the Heart, specifically 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). The parasympathetic Nervous system ( PSNS) is a division of the Autonomic nervous system (ANS along with the Sympathetic nervous system The vagus nerve (ˈveɪˌgəs (VĀ-gəs (also called pneumogastric nerve or cranial nerve X) is the tenth of twelve paired Cranial nerves, and is the The Sympathetic Nervous System ( SNS) is a branch of the Autonomic nervous system along with the Enteric nervous system and Parasympathetic nervous 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. This makes the SA node susceptible to autonomic influences. &trade The autonomic nervous system ( ANS) (or visceral nervous system) is the part of the Peripheral nervous system that acts as a Control
- Stimulation of the vagus nerve (parasympathetic fibers) causes a decrease in the SA node rate (thereby decreasing the heart rate). Parasympathetic fibers cannot change the force of contraction, however, because they only innervate the SA node and AV node (which control heart rate only).
- Stimulation via sympathetic fibers causes an increase in the SA node rate (thereby increasing the heart rate and force of contraction). Sympathetic fibers can increase the force of contraction because in addition to innervating the SA and AV nodes, they innervate the atria and ventricles themselves.
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. The right coronary artery (RCA originates above the right cusp of the Aortic valve. Myocardial infarction ( MI or AMI for acute myocardial infarction) also known as a heart attack, occurs when the blood supply In Medicine, ischemia ( Greek ισχαιμία, isch- is restriction hema or haema is Blood) is a restriction An anastomosis (plural anastomoses, from gr ἀναστόμωσις communicating opening) is a Network of streams that both branch out and reconnect If not, death of the affected cells will stop the SA node from triggering the heartbeat.
See also
References
External links
- sinuatrial+node at eMedicine Dictionary
- SUNY Figs 20:06-01 - "The conduction system of the heart. Cardiology (from Greek grc καρδίᾱ kardiā, "heart" and grc -λογία -logia) is the branch of Internal medicine The contractions of the Heart are controlled by chemical impulses which 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 eMedicine is an online clinical medical knowledge base that was founded in 1996 by Scott Plantz and Richard Lavely two medical doctors The State University of New York Health Science Center at Brooklyn, better known as SUNY Downstate Medical Center, is an academic medical center and is the only one of its kind "
- Diagram at gru.net
- Norman/Georgetown thoraxlesson4 (thoraxheartinternalner)
- http://www.healthyheart.nhs.uk/heart_works/heart03.shtml
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