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  • Atrial
  • Sick sinus syndrome is characterized by sinus node dysfunction with an atrial rate inappropriate for physiologic requirements. (aafp.org)
  • sick sinus sy
  • The aging of your SA node causes most cases of sick sinus syndrome, and there's no way to prevent that. (staywellsolutionsonline.com)
  • Sick sinus syndrome comprises a variety of conditions involving sinus node dysfunction and commonly affects elderly persons. (aafp.org)
  • Sick sinus syndrome has multiple manifestations on electrocardiogram, including sinus bradycardia, sinus arrest, sinoatrial block, and alternating patterns of bradycardia and tachycardia (bradycardia-tachycardia syndrome). (aafp.org)
  • Sick sinus syndrome is a generalized abnormality of cardiac impulse formation that may be caused by an intrinsic disease of the sinus node that makes it unable to perform its pacemaking function, or by extrinsic causes. (aafp.org)
  • Sick sinus syndrome is not a disease with a single etiology and pathogenesis but, rather, a collection of conditions in which the electrocardiogram (ECG) indicates sinus node dysfunction. (aafp.org)
  • 3 Degenerative fibrosis of nodal tissue is the most common cause of intrinsic changes in the sinoatrial node that lead to sick sinus syndrome. (aafp.org)
  • It is unclear whether inflammation, sinus node ischemia, or local autonomic neural effects lead to the development of sick sinus syndrome in patients with myocardial infarction. (aafp.org)
  • conduction
  • Increasing the complexity, each sinus beat may have multicentric origin, and the nature of conduction out of the node also seems to be variable in response to autonomic tone. (ahajournals.org)
  • Methods and Results- The kl/kl mice subjected to 20-hour restraint stress showed a high rate (20/30) of sudden death, which was associated with sinoatrial node dysfunction (conduction block or arrest). (ahajournals.org)
  • Nanomolar concentrations (10 or 100 nm) of TTX, which block TTX-sensitive iNa, slowed pacemaking in both intact SA node preparations and isolated SA node cells without a significant effect on SA node conduction. (ox.ac.uk)
  • In contrast, micromolar concentrations (1-30 microm) of TTX, which block TTX-resistant iNa as well as TTX-sensitive iNa, slowed both pacemaking and SA node conduction. (ox.ac.uk)
  • atrial
  • The human sinus node has been found to be anatomically constant and well localized, occupying an approximately 10-mm subepicardial region on the sulcus terminalis at the superior cavo-atrial junction. (ahajournals.org)
  • The SA node is located in the wall (myocardium) of the right atrium, laterally to the entrance of the superior vena cava in a region called the sinus venarum (hence sino- + atrial). (wikipedia.org)
  • The connective tissue, along with the paranodal cells insulate the SA node from the rest of the atrium, preventing the electrical activity of the atrial cells from affecting the SA node cells. (wikipedia.org)
  • The SA node cells are smaller and paler than the surrounding atrial cells, with the average cell being around 8 micrometers in diameter and 20-30 micrometers in length (1 micrometer= 0.000001 meter). (wikipedia.org)
  • Unlike the atrial cells, SA node cells contain fewer mitochondria (the power plant of the cell), fewer myofibers (the contractile machinery of the cell), and a smaller sarcoplasmic reticulum (a calcium storage organelle that releases calcium for contraction). (wikipedia.org)
  • This means that the SA node cells are less equipped to contract compared to the atrial and ventricular cells. (wikipedia.org)
  • This is again important in insulating the SA node from the surrounding atrial cells. (wikipedia.org)
  • It is concluded that two Na+ channel isoforms are important for the functioning of the SA node: neuronal (putative Nav1.1) and cardiac Nav1.5 isoforms are involved in pacemaking, although the cardiac Nav1.5 isoform alone is involved in the propagation of the action potential from the SA node to the surrounding atrial muscle. (ox.ac.uk)
  • Spontaneous action potentials of sino-atrial node (SAN) cells from pregnant mice exhibited higher automaticity (NP: 292±13bpm, P: 330±12bpm, p =0.047) and steeper diastolic depolarization (NP: 0.20±0.03V/s, P: 0.40±0.06V/s, p =0.004). (ahajournals.org)
  • The sinu-atrial node (SAN) is one of the impulse conducting system of the camel heart. (omicsonline.org)
  • Cholinergic inhibition of slow delayed-rectifier K+ current in guinea pig sino-atrial node is not mediated by muscarinic receptors. (aspetjournals.org)
  • We studied the effects of cholinergic agonists on slow delayed-rectifier K+ current (IKs) in isolated cells from the sino-atrial node (SAN) region of guinea pig heart, using patch-clamp procedures. (aspetjournals.org)
  • 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 that initiates atrial contraction by creating an action potential. (wikipedia.org)
  • In reality, the heart has several pacemakers known as autonomic foci, each which fires at its own intrinsic rate: SA node: 60-100 bpm Atrial foci: 60-80 bpm Junctional foci: 40-60 bpm Ventricular foci: 20-40 bpm The potentials will normally travel in order SA nodeatrial foci → junctional foci → ventricular foci Pacemaker potentials are fired not only by SA node, but also by the other foci. (wikipedia.org)
  • Consider a heart attack which damages the region of the heart between the SA node and the atrial foci. (wikipedia.org)
  • The electrical origin of atrial Purkinje fibers arrives from the sinoatrial node. (wikipedia.org)
  • periphery
  • Using immunocytochemistry and confocal microscopy, different distributions of the TTX-resistant cardiac isoform, Nav1.5, and the TTX-sensitive neuronal isoform, Nav1.1, were observed: Nav1.5 was absent from the centre of the SA node, but present in the periphery of the SA node, whereas Nav1.1 was present throughout the SA node. (ox.ac.uk)
  • contraction
  • Once the wave reaches the AV node, situated in the lower right atrium, it is delayed there before being conducted through the bundles of His and back up the Purkinje fibers, leading to a contraction of the ventricles. (wikipedia.org)
  • generate
  • This will be tested in three specific aims which will a) define the developmental timing and physiological/molecular properties that generate sinoatrial insulation, b) determine the source(s) of the cell population responsible for this insulation, and c) test the requirement of TGFb and BMP for proper generation of this sinoatrial node patterning. (grantome.com)
  • In short, they generate action potentials, but at a slower rate than sinoatrial node. (wikipedia.org)
  • therefore
  • however, they do so at a slower rate and therefore, if the SA node is working, it usually beats the AVN to it. (wikipedia.org)
  • intrinsic
  • Normally, all the foci will end up firing at the SA node rate, not their intrinsic rate. (wikipedia.org)
  • The other foci attempt to fire at their intrinsic rate, but they are activated by the SA node before they can fire. (wikipedia.org)
  • Thus, in the normal, healthy heart, only the SA node intrinsic rate is observable. (wikipedia.org)
  • slower
  • However, the other firing frequencies are slower than the one of the SA node (as seen above). (wikipedia.org)
  • mechanisms
  • Under the instruction of Dr. Takashi Mikawa, Dr. Bressan will explore the physiological and molecular mechanisms regulating sinoatrial node patterning at progressive developmental stages and be trained in advance techniques including retroviral mediated somatic transgenesis. (grantome.com)
  • ventricles
  • The cardioaccelerator center also sends additional fibers, forming the cardiac nerves via sympathetic ganglia (the cervical ganglia plus superior thoracic ganglia T1-T4) to both the SA and AV nodes, plus additional fibers to the atria and ventricles. (wikipedia.org)
  • significantly
  • Collectively, these studies will significantly advance our understanding of sinoatrial node development, while simultaneously allowing for Dr. Bressan to progress towards his long-term goal of becoming an independent researcher. (grantome.com)
  • bundle
  • The left and right branches of this bundle, and the Purkinje fibres, will also produce a spontaneous action potential at a rate of 30-40 beats per minute, so if the SA and AV node both fail to function, these cells can become pacemakers. (wikipedia.org)
  • The ECG allows observation of the heart electrical activity by visualizing waveform beat origin (typically from the sinoatrial or SA node) following down the bundle of HIS and ultimately stimulating the ventricles to contract forcing blood through the body. (wikipedia.org)
  • Junctional
  • A junctional escape complex is a normal response that may result from excessive vagal tone on the SA node (e.g. digoxin toxicity), a pathological slowing of the SA discharge, or a complete AV block. (wikipedia.org)
  • fails
  • This condition is sometimes confused with sinoatrial block, a condition in which the pacing impulse is generated, but fails to conduct through the myocardium. (wikipedia.org)
  • cells
  • Cells in the SA node spontaneously depolarize, ultimately resulting in contraction, approximately 100 times per minute. (wikipedia.org)