sinus node

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Related to sinus node: Sinus Node Dysfunction

sin·u·a·tri·al node

the mass of specialized cardiac muscle fibers that normally acts as the "pacemaker" of the cardiac conduction system; it lies under the epicardium at the upper end of the sulcus terminalis.

sinus node

sinus node

a cluster of hundreds of cells located in the right atrial wall of the heart, near the opening of the superior vena cava. It comprises a knot of modified heart muscle that generates impulses that travel swiftly throughout the muscle fibers of both atria, causing them to contract. Specialized pacemaker cells in the node have an intrinsic rhythm that is independent of any stimulation by nerve impulses from the brain and the spinal cord. Slender fusiform cells making up the sinoatrial node are largely filled with sarcoplasm but contain a few striated fibrillae. The cells are irregularly grouped together and, at the edge of the node, merge with the atrial musculature. The sinoatrial node will normally "fire" at a rhythmic rate of 70-75 beats/min. If the node fails to generate an impulse, pacemaker function will shift to another excitable component of the cardiac conduction system, such as the atrioventricular node or Purkinje's fibers. Certain hormones and various autonomic impulses can affect the sinoatrial node and cause it to "fire" faster, such as during strenuous physical activity. During a lifetime of 70 years the node generates about 2 billion impulses. Surgical implantation of an artificial pacemaker is a common procedure for individuals suffering from a defective sinoatrial node. Also called Keith-Flack node, Keith's bundle, pacemaker, sinoatrial node, sinus pacemaker. Compare atrioventricular node, Purkinje's network.

sinus node

Sinoatrial node, see there, SA node.


(nod) [L. nodus, knot]
1. A knot, knob, protuberance, or swelling.
2. A constricted region.
3. A small rounded organ or structure.

Aschoff node

Atrioventricular node.

atrioventricular node

Abbreviation: AV node
A node of specialized cardiac muscle fibers in the lower interatrial septum that receives impulses from the sinoatrial node and transmits them to the bundle of His.
Synonym: Aschoff node See: atrioventricular bundle; conduction system of the heart for illus

Bouchard node

In osteoarthritis, bony enlargement of the proximal interphalangeal joints.

ectopic lymph node

A cluster of immunologically active cells inside a malignant tumor. The node may represent an attempt by the body to destroy foreign antigens on the tumor cell surface.

Haygarth nodes

Joint swelling seen in rheumatoid arthritis.

Heberden nodes

See: Heberden nodes

hemal node

A vascular node that structurally resembles a lymph node, present in certain ungulates. Synonym: hemal gland

Hensen node

See: Hensen, Christian Andreas Victor
Enlarge picture

lymph node

A small encapsulated lymphoid organ that filters lymph. Lymph nodes are found at junctions or branches along the lymphatics. They provide sites where immune responses can be generated through the interaction of antigens, macrophages, dendritic cells and lymphocytes. See: illustration; immune response; inflammation; lymph; lymphocyteLymph nodes are 0.1-2.5 cm long kidney-shaped aggregates of lymphocytes and macrophages embedded in a meshwork reticulum composed of thin collagen fibers. At each lymph node, an artery enters through a surface indentation (the hilum) alongside an exiting vein and an exiting (efferent) lymphatic vessel; a number of afferent lymphatic vessels enter the lymph node at other sites. Inside lymph nodes, lymph slowly flows through endothelial sinuses lined by lymphocytes and macrophages. Macrophages remove macromolecules, particles, debris, and microorganisms from the lymph stream. Lymphocytes and antibodies move through the walls of the sinuses and into the passing lymph, while dendritic cells pass from the lymph into the lymphatic follicles, carrying antigens from the body's epithelia and from infected tissues. In the cortical region of the lymph node, the sinuses wind around lymphatic follicles, which are ovoid germinal centers packed with differentiating and proliferating B lymphocytes and surrounded by loose T lymphocytes. Lymphocytes and antibodies also enter and exit blood capillaries throughout the lymph node. Lymph nodes are most numerous in the neck, mediastinum, abdominal mesenteries, pelvis, the proximal limbs (the axillae and the groin), and along the posterior abdominal wall. Inside the chest and trunk, lymph nodes tend to be found along the veins near viscera.

Meynet nodes

See: Meynet nodes

neurofibril node

Ranvier's node.

Osler nodes

See: Osler nodes

Parrot nodes

See: Parrot nodes

piedric node

A node on the hair shaft seen in piedra.

primitive node

A knoblike structure at the anterior end of the primitive streak.
Synonym: Hensen knot; primitive knot

Ranvier node

See: Ranvier node

Schmorl node

A node seen in radiographs of the spine. It is caused by prolapse of the nucleus pulposus into the end plate of the vertebra.

sentinel node

1. A lymph node that receives drainage from a tumor and is likely to harbor metastatic disease before cancer cells have the opportunity to spread elsewhere.
2. Signal node.

signal node

Enlargement of one of the supraclavicular lymph nodes; usually indicative of primary carcinoma of thoracic or abdominal organs. Synonym: sentinel node (2); Troisier's node; Virchow node

singer's node

Noncancerous, callus-like growths on the inner parts of the vocal cords, usually caused by voice abuse or overuse. It is marked by a singer's hoarseness and an inability to produce the desired notes. It is treated by resting the voice. Surgical removal of the nodules is necessary if they do not respond to conservative therapy. Synonym: chorditis nodosa; laryngeal nodule

sinoatrial node

Abbreviation: SA node
A specialized group of cardiac muscle cells in the wall of the right atrium at the entrance of the superior vena cava. These cells depolarize spontaneously and rhythmically to initiate normal heartbeats.
Synonym: pacemaker (2); sinus node

sinus node

Sinoatrial node.

syphilitic node

Circumscribed swelling at the end of long bones due to congenital syphilis. The nodes are sensitive and painful during inflammation, esp. at night.
See: Parrot's nodes

Troisier's node

Signal node.

Virchow node

Signal node.


1. a recess, cavity, or channel, as (a) one in bone or (b) a dilated, valveless channel for venous blood.
2. an abnormal channel or fistula, permitting escape of pus. In common, unqualified usage, the word sinus refers to any of the cavities in the skull that are connected with the nasal cavity—the paranasal sinuses.

anal s's
furrows, with pouchlike recesses at their distal ends, separating the rectal columns; called also anal crypts.
basilar sinus
a dural venous sinus which runs on the floor of the cranial cavity and out through the foramen magnum.
cavernous sinus
an irregularly shaped venous channel between the layers of dura mater of the brain, one on either side of the body of the sphenoid bone and communicating across the midline. Several cranial nerves and, when present, the rete mirabile, course through this sinus.
cavernous sinus syndrome
lesions of the cavernous syndrome, caused by neoplasia or infectious agents, result in a dilated pupil and paralysis of the globe; vision is usually spared.
cerebral sinus
one of the ventricles of the brain.
cervical sinus
a temporary depression in the neck of the embryo containing the branchial arches.
circular sinus
the venous channel encircling the pituitary gland, formed by the two cavernous sinuses and the anterior and posterior intercavernous sinuses.
conchal sinus
cavity of the conchal bone.
coronary sinus
the terminal portion of the great cardiac vein, which lies in the cardiac sulcus between the left atrium and ventricle, and empties into the right atrium.
dermoid sinus, dermal sinus
see dermoid sinus.
dorsal sagittal sinus
a large dural venous sinus located within the falx cerebri.
dura mater venous sinus
large channels for venous blood forming an anastomosing system between the layers of the dura mater of the brain.
ethmoidal sinus
that paranasal sinus consisting of the ethmoidal cells collectively, and communicating with the nasal meatuses.
facial sinus
see malar abscess.
frontal sinus
one of the paired paranasal sinuses in the frontal bone, each communicating with the middle meatus of the ipsilateral nasal cavity.
hair sinus
see sinus hair.
infraorbital sinus
an air-filled recess in the head of birds which lies lateral to the nasal cavity into which it opens.
intercavernous sinus
channels connecting the two cavernous sinuses, one passing anterior and the other posterior to the stalk of the pituitary gland.
interdigitalis sinus
the cutaneous pouch, which lies between the claws of sheep and some other ruminants and whose wall contains apocrine glands, and whose duct surfaces on the skin just above the coronets; it serves as a trail gland.
lymphatic sinus
irregular, tortuous spaces within lymphoid tissues through which lymph flows.
maxillary sinus
one of the paired paranasal sinuses in the body of the maxilla on either side, opening into the middle meatus of the ipsilateral nasal cavity. In the horse it is divided into two compartments that communicate independently with the nasal chambers. All other sinuses of the horse communicate with the nasal chambers via the caudal maxillary sinus.
nasal sinus
see paranasal sinuses (below).
sinus nerve
a branch of the glossopharyngeal nerve; carries the afferent fibers of the stretch receptors in the wall of the carotid sinus.
sinus node
see sinoatrial node.
occipital sinus
a venous sinus between the layers of dura mater, passing along the midline of the cerebellum.
paranasal s's
mucosa-lined air cavities in bones of the skull, communicating with the nasal cavity and including ethmoidal, frontal, maxillary and sphenoidal sinuses.
petrosal sinus (inferior)
a venous channel arising from the cavernous sinus and draining into the internal jugular vein.
petrosal sinus (superior)
one arising from the cavernous sinus and draining into the transverse sinus of the dura mater.
prostatic sinus
the dorsolateral recess between the seminal colliculus and the wall of the urethra.
pulmonary trunk sinus
spaces between the wall of the pulmonary trunk and cusps of the pulmonary valve at its opening from the right ventricle.
red pulp sinus
vascular storage in the spleen into which capillaries empty.
sinus reflex arc
afferent fibers are in the sinus nerve; these connect with the cardioinhibitory and vasomotor centers which control blood pressure and heart rate via sympathetic fibers to blood vessels; provides a route for the sinus reflex which relates pressure in the carotid sinus to the performance of the circulatory system.
renal sinus
a recess in the substance of the kidney, occupied by the renal pelvis, calices, vessels, nerves and fat.
sagittal sinus (inferior)
a small venous sinus of the dura mater of large animals found between the cerebral hemispheres and opening into the straight sinus.
sagittal sinus (superior)
a venous sinus of the dura mater that courses between the cerebral hemispheres and ends in the confluence of sinuses.
scleral venous sinus
sigmoid sinus
a venous sinus of the dura mater on either side, continuous with the straight sinus and draining into the internal jugular vein of the same side.
sphenoidal sinus
one of the paired paranasal sinuses in the body of the sphenoid bone of some species. In the horse it communicates with the nasal cavity via the frontal and caudal maxillary sinuses.
sphenoparietal sinus
one of the venous sinuses of the dura mater, emptying into the cavernous sinus.
splenic sinus
dilated venous channels in the substance of the spleen. See also red pulp sinus (above).
straight sinus
a venous sinus of the dura mater formed by junction of the great cerebral vein and inferior sagittal sinus, and ending in the confluence of sinuses.
tarsal sinus
a space between the calcaneus and talus.
tentorial sinus
straight sinus.
transverse dura mater sinus
a large venous sinus that runs in the attached border of the cerebellar tentorium on either side of the skull.
transverse pericardial sinus
a passage within the pericardial sac, between the aorta and pulmonary trunk cranioventrally, and the left atrium and cranial vena cava dorsally.
tympanic sinus
a deep recess on the medial wall of the middle ear.
urachal sinus
an anomalous closure of the urachal canal in the newborn in which the opening at the umbilicus remains open. The bladder is normal. It is the cause of persistent infection and swelling at the umbilicus in the young animal and may lead to cystitis and pyelonephritis.
urethral s
a small cavity in the glans penis of the horse, above the urethral process; as a recess of the fossa glandis it is usually filled with a small mass (bean) of inspissated smegma.
urogenital sinus
an elongated sac formed by division of the cloaca in the early embryo, which ultimately forms most of the vestibule, urethra and vagina in the female, and some of the urethra in the male.
uterine sinus
venous channels in the wall of the uterus in pregnancy.
uteroplacental sinus
blood spaces between the placenta and uterine sinuses.
venae caval sinus
the posterior portion of the right atrium into which the inferior and the superior vena cava open.
sinus venarum
a chamber which is the greater part of the right atrium into which the great veins discharge.
venous sinus, sinus venosus
1. the common venous receptacle in the heart of the early embryo that receives blood from the umbilical and vitelline veins and from the body via the ducts of Cuvier.
2. sinus of venae cavae.
vertebral sinus
a continuation of part of the common occipital vein in birds; it emerges from the foramen magnum and accompanies the vertebral vein.
References in periodicals archive ?
If the origin is near the sinus node region or high in the atrium, the result would be a superior-to-inferior P wave axis; if it originates lower in the atrium, the resulting atrial depolarization would be an inferior-to-superior axis.
The heart rate of healthy persons displays beat-to-beat variations that results from fluctuations in autonomic nervous system activity at the sinus node.
This rhythm occurs when the sinus node, the natural pacemaker of the heart, fails to initiate the impulse and the AV node takes over (10).
Regulatory processes adequacy index (RPAI) reflects the correspondence between the parasympathetic activity of the autonomic nervous system and leading level of functioning sinus node, normally from 15 to 50.
The most common sustained arrhythmias are bradycardic: usually sinus node dysfunction or complete heart block.
The job of a pacemaker is to artificially take over the role of the heart's natural pacemaker, the sinus node.
They describe how ions, channels and currents work, then move to the elctrophysiological effects of cardiac autonomic activity, the mechanisms of arrhythmia, sinus node dysfunction and AV blocks, supraventricular tachycardia, differential diagnosis of wide complex tachycardia, ventricular tachycardia and ventricular fibrillation, sudden cardiac death and risk stratification, cardiac arrhythmia in patients with neuro-muscular disorders, syncope, pharmacologic therapy of arrhythmia, and electrical therapy for cardiac arrhythmia.
The underlying rhythm is normal until the sinus node fails to fire and the heart rate falls below 50/min (after sixth beat).
If the sinus node is damaged or compromised, as it can be, for example, by age-related fibrosis, the result is sick sinus syndrome (SSS), which can slow the heart rate to the point it causes exercise intolerance, fainting and fatigue.
The sinus node, a small group of specialized cells in the top right portion of the heart's upper chamber, serves as the pacemaker, initiating and orchestrating each heartbeat.
Another alternative is overdrive or synchronous biatrial pacing, especially for patients who have sinus node disease.
Examination of a rhythm strip shows a rhythm beginning in the sinus node where the P-P and R-R cycles vary more than 0.