Background- Homozygous mutant mice with a defect of klotho gene expression (kl/kl) show multiple age-related disorders and premature death from unknown causes.. 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). Heart rate and plasma norepinephrine of kl/kl mice, unlike those of wild-type (WT) mice, failed to increase during the stress. Intrinsic heart rate after pharmacological blockade of autonomic nerves in kl/kl mice was significantly lower than that in WT mice (380±33 versus 470±44 bpm; n=7). The sinus node recovery time after an overdrive pacing (600 bpm, 30 seconds) in kl/kl mice was significantly longer than in WT mice (392±37 versus 233±24 ms; n=6). In isolated sinoatrial node preparations, the positive chronotropic effect of isoproterenol was significantly less, whereas the negative chronotropic effect of acetylcholine was ...
In the century since the discovery by Keith and Flack of the sinoatrial node in the mole heart, a detailed mosaic of its cellular, anatomic, and electrophysiological properties has emerged. 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.1 Histologically, its ultrastructure of central P cells (likely corresponding to the leading pacemaker site) and outer transitional zone merging with surrounding atrial myocardium have been well characterized.1 Great progress also has been made in defining the ionic mechanisms responsible for the sinoatrial action potential and its spontaneous pacemaker activity, including important contributory roles for ICa,L, Ik, and the funny current, If.1 This morphologically discrete, unifocal sinus node is not the exclusive force behind clinical sinus rhythm, however. Detailed animal and human mapping has demonstrated that ...
Rationale: Autonomic nerves from sinoatrial node (SAN) ganglia are known to regulate SAN function. However, it is unclear whether remote pulmonary vein ganglia (PVG) also modulate SAN pacemaker rhythm. Objective: To investigate whether in the mouse heart PVG modulate SAN function. Methods and Results: In hearts from 45 C57BL and 7 Connexin40+/GFP mice, we used tyrosine-hydroxylase (TH) and choline-acetyltransferase (ChAT) immunofluorescence labeling to characterize adrenergic and cholinergic elements, repectively, within the PVG and SAN. PVG project postganglionic nerves to the SAN. TH and ChAT stained nerves, enter the SAN as an extensive, dense mesh-like neural network. Neurons in PVG are biphenotypic, containing ChAT and TH positive neurons. In Langendorff-perfused hearts, we compared effects of electrical stimulation of PVG, posterior (PRCVG) and anterior right vena cava ganglia (ARCVG) using 200-2000 ms trains of pulses (300μs, 0.2-0.6mA, 200Hz). Sympathetic and/or parasympathetic ...
The aim of this study was to investigate possible regulation of the hyperpolarization-activated current (I(f)) by cytosolic calcium in guinea-pig sino-atrial (SA) node cells. Isolated SA node cells were superfused with physiological saline solution (36 degrees C) and the perforated patch voltage-clamp technique used to record I(f) activated by hyperpolarizing voltage steps. A 10-min loading of SA node cells with the calcium chelator BAPTA (using 10 microM BAPTA-AM) significantly reduced the amplitude of I(f) at all potentials studied (69+/-8% at -80 mV, n=6). BAPTA loading also shifted the voltage of half-activation (V(h)) of the conductance from -83+/-2 mV in control to -93+/-2 mV in BAPTA (n=6) without significantly altering the slope of activation. The calmodulin antagonists W-7 (10 microM), calmidazolium (25 microM) and ophiobolin A (20 microM) caused similar reductions in I(f) amplitude (73+/-4, 86+/-9 and 59+/-6% at -80 mV, n=6, 5 and 4, respectively) and shifts in V(h) (11+/-3, 14+/-3 and 8+/-2
RATIONALE: Inositol 1,4,5-trisphosphate receptors (IP(3)Rs) have been implicated in the generation of arrhythmias and cardiac muscle nuclear signaling. However, in the mammalian sinoatrial node (SAN), where the heart beat originates, the expression and functional activity of IP(3)Rs have not been investigated. OBJECTIVES: To determine whether SAN express IP(3)Rs and which isoforms are present. To examine the response of the SAN to IP(3)R agonists and antagonist, and the potential role played by IP(3)Rs in cardiac pacemaking. METHODS AND RESULTS: The expression and distribution of IP(3)Rs were studied by reverse-transcription polymerase chain reaction, Western blotting, and immunolabeling. Ca(2+) signaling and electric activity in intact mouse SAN were measured with Ca(2+)-sensitive fluorescent dyes. We found that although the entire SAN expressed three IP(3)R mRNA isoforms, the type II IP(3)R (IP(3)R2) was the predominant protein isoform detected by Western blot using protein extracts from the SAN,
TY - JOUR. T1 - Synergistic dual automaticity in sinoatrial node cell and tissue models. AU - Zhang, Hong. AU - Joung, Boyoung. AU - Shinohara, Tetsuji. AU - Mei, Xi. AU - Chen, Peng-Sheng. AU - Lin, Shien-Fong. PY - 2010. Y1 - 2010. N2 - Background: The mechanism of sinoatrial node (SAN) automaticity is traditionally attributed to membrane ion currents. Recent evidence indicates spontaneous sarcoplasmic reticulum (SR) Ca2+ cycling also plays an important role. Methods and Results: A computer simulation on SAN cell and 1D tissue model was performed. In the SAN cells, SR Ca2+ cycling broadly modulated the sinus rate from 1.74 Hz to 3.87 Hz. Shortening of the junctional SR refilling time and increase of SR Ca2+ release were responsible for sinus rate acceleration. However, under the fast SR Ca2+ cycling, decreased L-type Ca2+ current (ICaL) resulted in irregular firing. When Ca2+ cycling was suppressed, If and ICaT both acted to stabilize the pacemaker rhythm, but ICaT had less effect than If. At ...
The advent of Ca2+ sensitive indicators, coupled to confocal imaging with simultaneous measurement of membrane potential, has permitted the detection of LCRs beneath the cell membrane during diastolic depolarization. Recent studies1,2,12 have shown that LCRs during diastolic depolarization activate NCX, which produces a large inward current1,9,19 in pacemaker cells, and enhances the rate of the later part of the diastolic depolarization.. The first novel finding of the present study is that the occurrence of LCRs during diastolic depolarization in rabbit sinoatrial nodal cells does not require the concomitant change in membrane potential. Thus, local LCRs occur in saponin "skinned" cells bathed at physiological [Ca2+] and during acute voltage clamp of spontaneously beating cells (Figures 1 and 3⇑). During the initial stage of voltage clamp, ie, the first "would-be" cycle, when SR Ca2+ load and RyR inactivation are the same as during the prior spontaneous beating, the LCR characteristics are ...
TY - JOUR. T1 - The calcium and voltage clocks in sinoatrial node automaticity. AU - Joung, Boyoung. AU - Ogawa, Masahiro. AU - Lin, Shien Fong. AU - Chen, Peng Sheng. PY - 2009/6/1. Y1 - 2009/6/1. N2 - Recent evidence indicates that the voltage (cyclic activation and deactivation of membrane ion channels) and Ca2+ clocks (rhythmic spontaneous sarcoplasmic reticulum Ca2+ release) jointly regulate sinoatrial node (SAN) automaticity. Since the intact SAN is a heterogeneous structure that includes multiple different cell types interacting with each other, the relative importance of the voltage and Ca2+ clocks for pacemaking may be variable in different regions of the SAN. Recently, we performed optical mapping in isolated and Langendorff-perfused canine right atria. We mapped the intracellular calcium (Cai) and membrane potentials of the intact SAN simultaneously. Using previously described criteria of the timing of the late diastolic Cai elevation (LDCAE) relative to the action potential upstroke ...
Methods and Results: Distribution of Islet-1+ cells in adult heart was investigated using transgenic mice with nuclear β-galactosidase inserted into the Islet-1 locus. nLacZ-positive cells were only present in 3 regions of the adult heart: clusters in the interatrial septum, scattered within the wall of the great vessels, and a strictly delimited cluster between right atrium and superior vena cava. Islet-1+ cells in the first type of clusters coexpressed markers for parasympathetic neurons. Positive cells in the great arteries coexpressed smooth muscle actin and β-myosin heavy chain, indicating a smooth muscle cell identity. Very few Islet-1+ cells within the outflow tract expressed the cardiomyocyte marker α-actinin. Islet-1+ cells in the right atrium coexpressed the sinoatrial node pacemaker cell marker HCN4. Cell number and localization remained unchanged between 1 to 18 months of age. Consistently Islet-1 mRNA was detected in human sinoatrial node. Islet-1+ cells could not be detected in ...
ABSTRACT: INTRODUCTION: Cardiac multicellular modeling has traditionally focused on ventricular electromechanics. More recently, models of the atria have started to emerge, and there is much interest in addressing sinoatrial node structure and function. METHODS AND RESULTS: We implemented a variety of one-dimensional sinoatrial models consisting of descriptions of central, transitional, and peripheral sinoatrial node cells, as well as rabbit or human atrial cells. These one-dimensional models were implemented using CMISS on an SGI Origin 2000 supercomputer. Intercellular coupling parameters recorded in experimental studies on sinoatrial node and atrial cell-pairs under-represent the electrotonic interactions that any cardiomyocyte would have in a multidimensional setting. Unsurprisingly, cell-to-cell coupling had to be scaled-up (by a factor of 5) in order to obtain a stable leading pacemaker site in the sinoatrial node center. Further critical parameters include the gradual increase in ...
The sinoatrial node (SA node), also known as sinus node, is a group of cells located in the wall of the right atrium of the heart. These cells have the ability to spontaneously produce an electrical impulse (action potential; see below for more details), that travels through the heart via the electrical conduction system (see figure 1) causing it to contract. In a healthy heart, the SA node continuously produces action potential, setting the rhythm of the heart and so is known as the hearts natural pacemaker. The rate of action potential production (and therefore the heart rate) is influenced by nerves that supply it. The sinoatrial node is a banana-shaped structure that varies in size, usually between 10-30 millimeters (mm) long, 5-7 mm wide, and 1-2 mm deep. 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). It is positioned roughly between a groove called the ...
How is isolated rabbit sino-atrial abbreviated? SA stands for isolated rabbit sino-atrial. SA is defined as isolated rabbit sino-atrial very rarely.
TY - JOUR. T1 - Heart failure differentially modulates natural (Sinoatrial node) and ectopic (pulmonary veins) pacemakers. T2 - Mechanism and therapeutic implication for atrial fibrillation. AU - Chan, Chao Shun. AU - Lin, Yung Kuo. AU - Chen, Yao Chang. AU - Lu, Yen Yu. AU - Chen, Shih Ann. AU - Chen, Yi Jen. PY - 2019/7/1. Y1 - 2019/7/1. N2 - Heart failure (HF) frequently coexists with atrial fibrillation (AF) and dysfunction of the sinoatrial node (SAN), the natural pacemaker. HF is associated with chronic adrenergic stimulation, neurohormonal activation, abnormal intracellular calcium handling, elevated cardiac filling pressure and atrial stretch, and fibrosis. Pulmonary veins (PVs), which are the points of onset of ectopic electrical activity, are the most crucial AF triggers. A crosstalk between the SAN and PVs determines PV arrhythmogenesis. HF has different effects on SAN and PV electrophysiological characteristics, which critically modulate the development of AF and sick sinus syndrome. ...
TY - JOUR. T1 - Abnormal response of superior sinoatrial node to sympathetic stimulation is a characteristic finding in patients with atrial fibrillation and symptomatic bradycardia. AU - Joung, Boyoung. AU - Hwang, Hye Jin. AU - Pak, Hui Nam. AU - Lee, Moon Hyoung. AU - Shen, Changyu. AU - Lin, Shien Fong. AU - Chen, Peng Sheng. PY - 2011/12. Y1 - 2011/12. N2 - Background-We hypothesized that unresponsiveness of superior sinoatrial node (SAN) to sympathetic stimulation is strongly associated with the development of symptomatic bradycardia in patients with atrial fibrillation (AF). Methods and Results-We performed 3D endocardial mapping in healthy controls (group 1, n=10) and patients with AF without (group 2, n=57) or with (group 3, n=15) symptomatic bradycardia at baseline and during isoproterenol infusion. Corrected SAN recovery time was abnormal in 0%, 11%, and 36% of groups 1, 2, and 3, respectively (P=0.02). At baseline, 90%, 26%, and 7% (P,0.001) of the patients had multicentric SAN ...
TY - JOUR. T1 - Measurement of funny current (I(f)) channel mRNA in human atrial tissue. T2 - Correlation with left atrial filling pressure and atrial fibrillation. AU - Lai, Ling Ping. AU - Su, Ming Jai. AU - Lin, Jiunn Lee. AU - Tsai, Chang Her. AU - Lin, Fang Yue. AU - Chen, Yih Sharng. AU - Hwang, Juey Jen. AU - Stephen Huang, Shoei K.. AU - Tseng, Yung Zu. AU - Lien, Wen Pin. PY - 1999/1/1. Y1 - 1999/1/1. N2 - Introduction: The funny current (I(f)) contributes to phase IV spontaneous depolarization in cardiac pacemaker tissue. Enhanced I(f) activity in myocardial tissue may lead to increased automaticity and therefore tachyarrhythmia. We measured the amount of I(f) activity in the messenger ribonucleic acid (mRNA) in human atrial tissue and correlated the mRNA amount to left atrial filling pressure and atrial fibrillation (AF). Methods and Results: A total of 34 patients undergoing open heart surgery were included (15 men and 19 women, aged 55 ± 10 years). Atrial tissue was obtained from ...
Free, official information about 2012 (and also 2013-2015) ICD-9-CM diagnosis code 427.81, including coding notes, detailed descriptions, index cross-references and ICD-10-CM conversion.
Cardiac pacemaker cells of the sinoatrial node initiate and maintain the rhythmic beating of the heart. This function requires that pacemaker cells be insulated...
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. Carbachol (5 nM to 10 microM) inhibited IKs in guinea pig SAN cells in the absence of previous beta-adrenergic stimulation and in cells pretreated with 8-(4-chlorophenylthio)-cAMP. Neither the muscarinic antagonist atropine nor the nicotinic antagonist hexamethonium antagonized carbachol inhibition of the current. Similar results were obtained with other cholinergic agonists. Cholinergic stimulation of the muscarinic K+ current was successfully antagonized by atropine in SAN cells where inhibition of IKs persisted. Therefore, the lack of antagonist effects on inhibition of IKs cannot be attributed to either an absence of muscarinic cholinoceptors on SAN cells or a loss of antagonist activity under our experimental conditions. These data demonstrate that cholinergic agonists, including the endogenous ...
In a randomized, observer-blind study, the effect of incremental doses of pindolol 0.001, 0.002, 0.003, and 0.004 mg/kg IV and propranolol 0.01, 0.02, 0.03, and 0.04 mg/kg IV on SA nodal recovery time (SNRT) and atrioventricular conduction interval (AH) was assessed in 20 patients (15 men and 5 women age range thirty to seventy-two, mean age fifty-three). AH and His bundle-to-ventricle (HV) intervals and SNRT were measured at spontaneous heart rate and at incremental atrial pacing rates (80, 100, 120, 140 bpm). Both drugs caused significant beta blockade as estimated by the percentage suppression of heart rate increment induced by 3 mcg isoproterenol administered intravenously (pindolol 67.6±5.3%, ...
Free Online Library: Sinoatrial node artery arising from posterolateral branch of right coronary artery: definition by screening consecutive 1500 coronary angiographies/Sag koroner arter posterolateral dalindan cikan sinoatriyal nod arteri: Ardisik 1500 koroner anjiyografi taramasi ile tanimlama.(Original Investigation/Ozgun Arastirma) by The Anatolian Journal of Cardiology (Anadolu Kardiyoloji Dergisi); Health, general Angiography
Spontaneous activation and contraction of the heart are a consequence of the specialized pacemaking tissue in these anatomic locales. As described in Chap. 238, action potentials in the heart are regionally heterogeneous. The action potentials in cells isolated from nodal tissue are distinct from those recorded from atrial and ventricular myocytes (Fig. 239-1). The complement of ionic currents present in nodal cells results in a less negative resting membrane potential compared with atrial or ventricular myocytes. Electrical diastole in nodal cells is characterized by slow diastolic depolarization (phase 4), which generates an action potential as the membrane voltage reaches threshold. The action potential upstrokes (phase 0) are slow compared with atrial or ventricular myocytes, being mediated by calcium rather than sodium current. Cells with properties of SA and AV nodal tissue are electrically connected to the remainder of the myocardium by cells with an electrophysiologic phenotype between ...
OBJECTIVE: The L-type Ca(2+) current (I(Ca,L)) contributes to the generation and modulation of the pacemaker action potential (AP). We investigated facilitation of I(Ca,L) in sino-atrial cells. METHODS: Facilitation was studied in regularly-beating cells isolated enzymatically from young albino rabbits (0.8-1 kg). We used the whole-cell patch-clamp technique to vary the frequency of the test depolarizations evoked at -10 mV or the conditioning diastolic membrane potential prior to the test pulse. RESULTS: High frequencies (range 0.2-3.5 Hz) slowed the decay kinetics of I(Ca,L) evoked from a holding potential (HP) of -80 mV in 68% of cells resulting in a larger Ca(2+) influx during the test pulse. The amount of facilitation increased progressively between 0.2 and 3.0 Hz. When the frequency was changed from 0.1 to 1 Hz, the averaged increase in the time integral of I(Ca,L) was 27+/-7% (n=22). Application of conditioning voltages between -80 and -50 mV induced similar facilitation of I(Ca,L) in 73% of
... refers to the accelerated generation of an action potential by either normal pacemaker tissue (enhanced normal automaticity) or by abnormal tissue within the myocardium (abnormal automaticity). The discharge rate of norm
ible dose of sildenafil during 1 month. In patients with Since endothelial dysfunction is associated with vas- CHF, sildenafil significantly reduced blood pressure, cular inflammation, platelet activation, and rapid pro- resting heart rate and attenuated the heart rate incre- gression of atherosclerosis and its adverse events, strate- ment (6-min treadmill-walking test and maximal exer- gies that enhance NO bioavailability may have a positive cise test, Figure 3) which was attributed to the modula- impact on outcomes in patients with coronary artery dis- tion of the effects of the NO-cGMP pathway on the ease (CAD). Therefore, Halcox et al. [40] hypothesized pacemaker activity of sinoatrial node cells [43]. More- that PDE 5 inhibition with sildenafil may abrogate coro- nary and peripheral vascular endothelial dysfunction in cise and increased the maximal exercise capacity. Treat- patients with CAD, inhibit platelet activation, and ame- ment was associated with more adverse symptoms, liorate ...
Background. The ischemic damage of the sinus node (SN) is a well known cause of cardiac arrhythmias and can be a consequence of any flow abnormality in the sinus node artery (SNA). Accordingly we aimed this retrospective study to: (1) evaluate the suitability of the standard coronary angiography to study the SNA and (2) determine if the percentage of subjects with a positive retrospective history of supra-ventricular arrhythmias (SVA) differs in patients with normal and diseased SNA ascertained at the time of coronary angiography.Methods and Results. Out of the 541 coronary angiograms reviewed the SNA was visible for its entire course in 486 cases (89.8%). It was found to arise from the right side of the coronary circulation in 266 cases (54.7%) slightly more often than from the left, 219 cases (45.1%). One patient had 2 distinct SNA arising from either side of the coronary circulation. For the second objective, we studied the 333 patients with: (a) coronary artery disease (CAD), (b) properly evaluable
Mladen Boban, John L. Atlee, Martin Vicenzi, John P. Kampine, Zeljko J. Bosnjak; Anesthetics and Automaticity in Latent Pacemaker Fibers: IV. Effects of Isoflurane and Epinephrine or Norepinephrine on Automaticity of Dominant and Subsidiary Atrial Pacemakers in the Canine Heart. Anesthesiology 1993;79(3):555-562. Download citation file:. ...
Automaticity refers to a cardiac muscle cell firing off an impulse on its own. All of the cells in the heart have the ability to initiate an action potential; however, only some of these cells are designed to routinely trigger heart beats. These cells are found in the conduction system of the heart and include the SA node, AV node, Bundle of His and Purkinje fibers. The sinoatrial node is a single specialized location in the atrium that has a higher automaticity (a faster pacemaker) than the rest of the heart and, therefore, is usually responsible for setting the heart rate and initiating each heart beat. Any part of the heart that initiates an impulse without waiting for the sinoatrial node is called an ectopic focus and is, by definition, a pathological phenomenon. This may cause a single premature beat now and then, or, if the ectopic focus fires more often than the sinoatrial node, it can produce a sustained abnormal rhythm. Rhythms produced by an ectopic focus in the atria, or by the ...
Wandering atrial pacemaker (WAP) is an atrial arrhythmia that occurs when the natural cardiac pacemaker site shifts between the sinoatrial node (SA node), the atria, and/or the atrioventricular node (AV node). This shifting of the pacemaker from the SA node to adjacent tissues is identifiable on ECG Lead II by morphological changes in the P-wave; sinus beats have smooth upright P waves, while atrial beats have flattened, notched, or diphasic P-waves. It is often seen in the very young, very old, and in athletes, and rarely causes symptoms or requires treatment.[citation needed] Wandering pacemaker is usually caused by varying vagal tone. With increased vagal tone the SA Node slows, allowing a pacemaker in the atria or AV Nodal area, which may briefly become slightly faster. After vagal tone decreases, the SA Node assumes its natural pace. A wandering atrial pacemaker, also termed multifocal atrial rhythm, is present when there are three or more ectopic foci within the atrial myocardium that ...
Sinoatrial nodal cells (SANCs) generate spontaneous action potentials (APs) that control the cardiac rate. The brain modulates SANC automaticity, via the autonomic nervous system, by stimulating membrane receptors that activate (adrenergic) or inactivate (cholinergic) adenylyl cyclase (AC). However, these opposing afferents are not simply additive. We showed that activation of adrenergic signaling increases AC-cAMP/PKA signaling, which mediates the increase in the SANC AP firing rate (i.e., positive chronotropic modulation). However, there is a limited understanding of the underlying internal pacemaker mechanisms involved in the crosstalk between cholinergic receptors and the decrease in the SANC AP firing rate (i.e., negative chronotropic modulation). We hypothesize that changes in AC-cAMP/PKA activity are crucial for mediating either decrease or increase in the AP firing rate and that the change in rate is due to both internal and membrane mechanisms. In cultured adult rabbit pacemaker cells infected
Under normal physiologic conditions, the dominant pacemaker cells of the heart lie within the sinoatrial node; in adults, these pacemaker cells fire at rates between 60 to 100 beats per minute (i.e., faster than cells in any other cardiac region, See Figure 3). Even at rest, modulation by the autonomic nervous system dominates, with the primary drive from the parasympathetics; at rest or during sleep, the sinoatrial nodal rate decreases to about 75 beats per minute (bpm) or even slower.. In addition to pacemaker cells of the sinoatrial node, other cells within the conduction system are capable of developing autorhythmicity, specifically those within the atrioventricular node (junction region) and His-Purkinje system. Yet, rhythms generated within these cells are in a much lower range (25 to 55 bpm), hence not altering the intrinsic atrial rates (Figure 2). These lower rate rhythms are commonly referred to as ventricular escape rhythms and are important for patient survival, since they maintain ...
The objective of the study was to evaluate the effect of ibutilide on canine cardiac sinoatrial and atrioventricular nodes (AVNs). For this purpose, 18 mongrel dogs were injected intravenously with ibutilide and the changes in heart rate, sinus node recovery time, and AVN were measured. Our data show that ibutilide administration caused significant suppression of the sinus atrial node, the peak response time was 20-30 min, and the heart rate was restored to pre-drug administration level. After receiving ibutilide, 1 animal had a 5 s sinus pause, and after 5 min of ibutilide administration, 1 dog showed 2:1 atrioventricular conduction. Therefore, it was concluded that ibutilide had a suppressive effect on the sinoatrial node and AVN. ...
Abstract:. Background: For chronic kidney disease patients undergoing maintenance hemodialysis (HD), the risk to die from sudden cardiac death (SCD) is 14x higher compared to patients with a history of cardiovascular disease and normal kidney function. Traditional SCD risk factors cannot explain this high rate. Two recent human studies using implantable loop recorders surprisingly point towards bradycardia and asystole as the prevailing arrhythmias causing SCD in HD patients. This suggests a decisive role of the sinus node. Objective: To identify the effect of altered electrolyte levels (as systematically occurring in HD patients) on pacemaking in a computational model of human sinus node cells. Methods: We enhanced the Fabbri et al. model of human sinus node cells to account for the dynamic intracellular balance of all considered electrolytes. The model was exposed to clinically relevant extracellular electrolyte concentrations of potassium, sodium, and calcium to study their effect on ...
Looking for nodal artery? Find out information about nodal artery. blood vessel that conveys blood away from the heart heart, muscular organ that pumps blood to all parts of the body. The rhythmic beating of the heart is a... Explanation of nodal artery
Properties of the cardiac muscle AUTOMATICITY CONDUCTIVITY CONTRACTILITY EXCITABILITY REFRACTORY PERIODS 1. AUTOMATICITY is the unique ability of the cells in the SA node (pacemaker cells) to generate an action potential without being stimulated.
The sinoatrial node (SAN) is the normal pacemaker of the mammalian heart. Over several decades, a large amount of data on the ionic mechanisms underly...
We have investigated the concentration-dependent modulation, by the novel class III antiarrhythmic compound NE-10064, of the delayed potassium channel current Iks in isolated guinea pig sinoatrial nodal (SAN) and ventricular cells. At concentrations greater than 1 micron, the drug potently inhibited Iks in each of the cell types investigated. The concentration-dependent inhibition of Iks (IC50 = 700 nM) was the same in ventricular and SAN cells. At near-threshold drug concentrations, we also observed increases of Iks activity in both SAN and ventricular cells. The NE-10064-induced enhancement of Iks was more pronounced at voltages near the Iks activation threshold (0 mV), than at more positive voltages in both cell types. Furthermore, the agonistic effects of the drug were more prominent before steady-state effects of the compound were attained, which suggests parallel agonistic and antagonistic pathways. Our results demonstrate that Iks channels in cells of the sinoatrial node region of the ...
In this study of interactions occurring within the heart, isolated superfused strips of rabbit atria, containing the sinoatrial (s.a.) node, were subjected to sinusoidal subthreshold current pulses of varied frequencies and intensities. A.C. current
TY - JOUR. T1 - Impact of manipulation of energy substrates on sinus nodal rhythm. AU - Maruyama, Hiroko. AU - Ito, Masanori. AU - Goda, Nobuhito. AU - Adachi-Akahane, Satomi. PY - 2014/1. Y1 - 2014/1. N2 - Background: The high energy demand of the heart is supported by metabolic flexibility in the utilization of energy substrates for adenosine triphosphate (ATP) synthesis. To investigate the roles of glucose and long-chain fatty acids (FA) as energy substrates in sinus nodal rhythm, we developed an isolated mouse atrial preparation and studied the effects of manipulating these energy substrates on atrial beating rate. Methods: The spontaneous beating rate of isolated atria from mouse was measured at resting tension in a modified Tyrode solution that was gassed with 100% O2 at 37°C and contained 1 of the following sets of energy substrates: 10 mM glucose plus 0.4 mM palmitate (control), 5 mM glucose plus 0.4 mM palmitate (low glucose), or 10 mM glucose without palmitate (FA (-)). Atria were ...
0:06Skip to 0 minutes and 6 secondsWere going to look at the function of the heart. The main function of the heart is to supply blood to the tissues of the body, delivering oxygen and nutrients to them. Now, the heart is able to function because it is able to generate its own electrical activity. And this starts in the region known as the pacemaker, or the sinoatrial node, that is located in the right atrium. The electrical activity begins in the sinoatrial node, then spreads across the rest of the atrium, through to the other atrium, and then down into the ventricles. This causes the atria to contract before the ventricles.. 0:49Skip to 0 minutes and 49 secondsNow, the electrical activity of the heart can be measured using the electrocardiogram, or the ECG, that can measure the electrical activity of the heart, and this is depicted by letters of the alphabet P, QRS, and T. Now when the electrical activity of the heart passes through the atria, this causes the atria to contract and, as a result ...
Results of the present study suggest that the neural sympathetic discharge activity (MSNA) was markedly higher in subjects with active UC than in healthy controls. In addition, heart rate, LFRR normalized units, and LF-to-HF ratio were greater and HFRR was lower in patients, suggesting a shift of the sympathovagal modulation of the sinoatrial node toward a sympathetic predominance and parasympathetic reduction, compared with controls. As to this latter aspect, it must be pointed out that power spectrum analysis of R-R interval variability does not provide a direct measure of the neural autonomic activity directed to the heart, but, rather, it furnishes a broad noninvasive marker of the relationship between neural modulation and target organ, i.e., the sinoatrial node responsiveness (25, 29, 38).. In patients, despite the elevated values of MSNA, plasma norepinephrine was only slightly higher than in controls. It should be recalled that plasma norepinephrine levels provide imprecise estimate of ...
What is the difference between SA node and AV node? SA node generates cardiac action potential while AV node receives the action potential from the SA node...
An electrical stimulus is generated by the sinus node (also called the sinoatrial node, or SA node). This is a small mass of specialized tissue located in the right atrium (right upper chamber) of the heart. The sinus node generates an electrical stimulus regularly (60 to 100 times per minute under normal conditions). The atria are then activated. The electrical stimulus travels down through the conduction pathways (similar to the way electricity flows through power lines from the power plant to your house) and causes the hearts ventricles to contract and pump out blood. The right and left atria (the two upper chambers of the heart) are stimulated first and contract for a short period of time before the right and left ventricles (the two lower chambers of the heart). The electrical impulse travels from the sinus node to the atrioventricular node (also called AV node). There, impulses are slowed down for a very short period, then continue down the conduction pathway via the bundle of His into ...
An electrical stimulus is generated by the sinus node (also called the sinoatrial node, or SA node), which is a small mass of specialized tissue located in the right atrium (right upper chamber) of the heart.. The sinus node generates an electrical stimulus regularly at 60 to 100 times per minute under normal conditions. This electrical stimulus travels down through the conduction pathways (similar to the way electricity flows through power lines from the power plant to your house) and causes the hearts lower chambers to contract and pump out blood. The right and left atria (the two upper chambers of the heart) are stimulated first and contract a short period of time before the right and left ventricles (the two lower chambers of the heart).. The electrical impulse travels from the sinus node to the atrioventricular node (also called AV node), where impulses are slowed down for a very short period, then continue down the conduction pathway via the bundle of His into the ventricles. The bundle ...
An electrical stimulus is generated by the sinus node (also called the sinoatrial node, or SA node), which is a small mass of specialized tissue located in the right atrium (right upper chamber) of the heart.. The sinus node generates an electrical stimulus regularly at 60 to 100 times per minute under normal conditions. This electrical stimulus travels down through the conduction pathways (similar to the way electricity flows through power lines from the power plant to your house) and causes the hearts lower chambers to contract and pump out blood. The right and left atria (the two upper chambers of the heart) are stimulated first and contract a short period of time before the right and left ventricles (the two lower chambers of the heart).. The electrical impulse travels from the sinus node to the atrioventricular node (also called AV node), where impulses are slowed down for a very short period, then continue down the conduction pathway via the bundle of His into the ventricles. The bundle ...
Choate, J.K.; Paterson, D.J., 1998: Inhibition of nitric oxide synthase increases the positive chronotropic response to sympathetic nerve stimulation in the isolated guinea-pig atria
Rev Bras Anestesiol ARTIGO CIENTÍFICO 2007; 57: 5: SCIENTIFIC ARTICLE Estudo Prospectivo das Repercussões de Baixas Doses de Remifentanil na Função Sinoatrial e na Condução e Refratariedade Cardíaca*
Like CNG channels, the HCN cation channels are members of the six-transmembrane superfamily (Kaupp and Seifert, 2001; Biel et al., 2002; Robinson and Siegelbaum, 2003). In contrast to most other voltage-gated channels, HCN channels open upon hyperpolarization and close at positive potential. The cyclic nucleotides cAMP and cGMP enhance HCN channel activity by shifting the activation curve of the channels to more positive voltages. The stimulatory effect of cyclic nucleotides does not depend on protein phosphorylation but is caused by direct interaction with the HCN channel protein. The current produced by HCN channels, termed Ih, If, or Iq, is found in a variety of excitable cells, including neurones, cardiac pacemaker cells, and photoreceptors (Pape, 1996; Robinson and Siegelbaum, 2003). The best-understood function of Ih is to control heart rate and rhythm by acting as "pacemaker current" in the sinoatrial (SA) node (Stieber et al., 2004). Ih is activated during the membrane hyperpolarization ...
deletion, revealed that ISL1 within SAN is a requirement for early embryonic viability. RNA-sequencing (RNA-seq) analyses of FACS-purified cells from ISL1-deficient SANs revealed that a number of genes critical for SAN function, including those encoding transcription factors and ion channels, were downstream of ISL1. Chromatin immunoprecipitation assays performed with anti-ISL1 antibodies and chromatin extracts from FACS-purified SAN cells demonstrated that ISL1 directly binds genomic regions within several genes required for normal pacemaker function, including subunits of the L-type calcium channel ...
A negative chronotropic effect is an action to the heart that causes the organ to beat slower than before. This is often achieved by increasing vagal or parasympathetic stimulation or decreasing...