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Topic: Ventricular action potential

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In the News (Thu 20 Jun 19)

  Wikipedia: Action potential
In his discovery of "animal electricity," Luigi Galvani elicited an action potential through contact of his scalpel with the sciatic motor nerve of a frog he was dissecting, causing one of its legs to kick as in life.
Because the salty cytoplasm of the axon is electrically conductive, and because the myelin inhibits charge leakage through the membrane, depolarization at one node is sufficient to elevate the voltage at a neighboring node to the threshold for action potential initiation.
Action potentials are measured with the recording techniques of electrophysiology.
www.factbook.org /wikipedia/en/a/ac/action_potential.html   (902 words)

 Action potential - Biocrawler   (Site not responding. Last check: 2007-10-13)
While the cell is at resting cell potential the electric forces between the sodium and potassium of the neuron is counterbalanced by the "diffusive forces," creating a state of equilibrium.
The depolarization phase of an action potential is due to the opening of voltage-gated ion channels, either sodium channels or calcium channels or a combination of both, depending on the particular membrane.
Where membrane has undergone an action potential a refractory period follows, during which a second action potential is inhibited due to the reversible inactivation of ion channels.
www.biocrawler.com /encyclopedia/Action_potential   (1388 words)

 CBER - Guidance for Industry: S7B Nonclinical Evaluation of the Potential for Delayed Ventricular Repolarization (QT ...
Ventricular repolarization, determined by the duration of the cardiac action potential, is a complex physiological process.
phase 0: The upstroke of the action potential is primarily a consequence of a rapid, transient influx of Na Na
The objectives of studies are to: (1) identify the potential of a test substance and its metabolites to delay ventricular repolarization, and (2) relate the extent of delayed ventricular repolarization to the concentrations of a test substance and its metabolites.
www.fda.gov /cber/gdlns/ichqt.htm   (3587 words)

 Antiarrhythmic Effects of Ranolazine in a Guinea Pig in Vitro Model of Long-QT Syndrome -- Wu et al. 310 (2): 599 -- ...
action potential duration (APD) and the QT interval.
of the ventricular action potential and the QT interval.
of the action potential, and action potential duration.
jpet.aspetjournals.org /cgi/content/full/310/2/599   (4379 words)

 Ventricular action potential - Wikipedia, the free encyclopedia
At rest, the ventricular myocyte membrane potential is about -90 mV, which is close to the potassium reversal potential.
The beginning of the action potential, phase 1, specialized membrane proteins (voltage-gated sodium channels) in the cell membrane selectively allow sodium ions to enter the cell.
Repolarization is accomplished by channels that open slowly and are mostly activated at the end of the action potential (slow delayed-rectifier channels), and channels that open quickly but are inactivated until the end of the action potential (fast delayed rectifier channels).
en.wikipedia.org /wiki/Ventricular_action_potential   (291 words)

 Action potential - Wikipedia, the free encyclopedia
The potential difference across the membrane at rest is called the resting potential and is approximately -70 mV in neurons, with the negative sign indicating that the inside of the cell is negative with respect to the outside.
Establishment of a membrane potential of around +40 mV closes the voltage-sensitive inactivation gates of the sodium channels, which are sensitive to the now-positive membrane potential gradient, preventing further influx of sodium.
Thus the membrane potential dips below the normal resting membrane potential of the cell for a brief moment; this dip of hyperpolarization is known as the undershoot.
en.wikipedia.org /wiki/Action_potential   (3557 words)

 :Pharmacology:SUNY Upstate Medical University
The excitatory inward and inhibitory outward ionic currents associated with the cardiac action potential are directly modulated by membrane voltage while the background potassium current (IK1) rectifies upon membrane depolarization due to intracellular polyamine (e.g.
We continue to investigate the regulation of atrial and ventricular gap junctions and specific connexin gap junctions formed by connexins -40, -43, and -45 by pacemaker, atrial, and ventricular action potential waveforms at different rates of stimulation ranging from 240 (tachycardia) to 30 (bradycardia) beats/min.
Action potential modulation of connexin40 gap junctional conductance.
www.upstate.edu /pharm/faculty.php?ID=veenstrr   (444 words)

 Luo-Rudy model development
Reconstruction of the action potential of ventricular myocardial fibres.
Action potential and contractility changes in [Na(+)](i) overloaded cardiac myocytes: a simulation study.
Action potential propagation in inhomogeneous cardiac tissue: safety factor considerations and ionic mechanism.
www.cwru.edu /med/CBRTC/LRdOnline/development.htm   (1681 words)

 Dispersion of Ventricular Repolarization and Ventricular Fibrillation in Left Ventricular Hypertrophy: Influence of ...
potential duration (APD) and increased dispersion of APD that
the spontaneous occurrence of ventricular fibrillation was not
Aronson RS (1980) Characteristics of action potentials of hypertrophied myocardium from rats with renal hypertension.
jpet.aspetjournals.org /cgi/content/full/292/1/381   (3657 words)

 Cardiac Action Potential
The fact that a cardiac action potential is long implies that the refractory period is long too.
Thus it opens as an action potential ends, which between action potentials keeps the membrane potential down much closer to the K+ equilibrium potential and thus a long way from the threshold.
Below you see the action potential in an SA node and the times that four voltage gated ion channels are open.
courses.washington.edu /conj/heart/cardiacAP.htm   (842 words)

and the action potential was obtained from the midventricle.
Note that the shape of the atrial action potential is different from the ventricular one and that the atrial and vetricular action potentials show alternate firings.
Action potential (top trace) and muscle tension (bottom trace) were recorded simultaneously from the frog heart.
advan.physiology.org /cgi/content/full/25/3/176   (4360 words)

 HERG Channel (Dys)function Revealed by Dynamic Action Potential Clamp Technique -- Berecki et al. 88 (1): 566 -- ...
by the free-running action potential of the ventricular cell.
mutation caused a frequency-dependent increase of the action
Action potential conduction between a ventricular cell model and an isolated ventricular cell.
www.biophysj.org /cgi/content/full/88/1/566   (4868 words)

 Antiarrhythmics---from cell to clinic: past, present, and future -- Hancox et al. 84 (1): 14 -- Heart
The membrane potential is controlled by the experimenter, allowing measurements of whole cell membrane current to be made in response to applied voltage commands.
The effects of lidocaine on intracellular and extracellular potentials, activation and ventricular arrhythmias during acute regional ischaemia in the isolated porcine heart.
Prolongation of monophasic action potential duration and the refractory period in the human heart by tedisamil, a new potassium channel blocking agent.
heart.bmjjournals.com /cgi/content/full/84/1/14   (6152 words)

 References   (Site not responding. Last check: 2007-10-13)
A model of the ventricular cardiac action potential: Depolarization, repolarization, and their interaction.
A dynamic model of the cardiac ventricular action potential: I. simulations of ionic currents and concentration changes.
A dynamic model of the cardiac ventricular action potential: Ii.
www.cc.utah.edu /~qn5349/ep/node16.html   (143 words)

 355 lecture on blood   (Site not responding. Last check: 2007-10-13)
Phases of the Action Potential of a Purkinje heart muscle cell.
In some ventricular muscles there is a distinctive "notch" at this time.
greater outside the cell, the resulting influx of Ca prevents the membrane potential from returning to the resting level and instead results in a plateau period where the membrane potential remains around 0 mv to slightly positive.
www.bios.niu.edu /griffiths/355ventricularAP.htm   (185 words)

 Human Ventricular Action Potential Duration During Short and Long Cycles: Rapid Modulation by Ischemia -- Taggart et ...
Gettes LS, Marchanse N, Surawicz B. Effect of premature depolarization on the duration of action potentials in Purkinje and ventricular fibers of the moderator band of the pig heart: role of proximity and the duration of the preceding action potential.
Monophasic action potentials in patients with coronary artery disease: reproducibility and electrical restitution and conduction at different stimulation rates.
Injury current and gradients of diastolic stimulation threshold, TQ potential, and extracellular potassium concentration during acute regional ischemia in the isolated perfused pig heart.
circ.ahajournals.org /cgi/content/full/94/10/2526   (5639 words)

 bSys GmbH, HERG Testing
The QT interval as measured in the ECG is a measure of the duration of ventricular depolarization and repolarization.
The cardiac action potential is the net result of the activity of many ion channels and transporters.
Phase 2: The plateau of the action potential is a result of combination of calcium influx through Cav1.2 channels (L-type) and simultaneous outward repolarizing potassium currents.
www.bsys.ch /qtprolongation.html   (310 words)

 [No title]
Discuss the role of K channels in the ventricular action potential.
Draw an action potential and label each phase; indicate on your drawing which K channel(s), if any, contribute(s) to each phase.
Compare and contrast synaptic potentials and action potentials with an emphasis on differences in ion channels and the biophysical characteristics of those channels (e.g., magnitude and time course of each potential, gating differences etc).
www.ttuhsc.edu /SOM/physiology/Courses/2004PreliminaryExam.doc   (1384 words)

 Intracellular Ca2+ Dynamics and the Stability of Ventricular Tachycardia -- Chudin et al. 77 (6): 2930 -- Biophysical ...
Ventricular fibrillation (VF), the major cause of sudden cardiac death, is typically preceded by ventricular tachycardia (VT),
Ventricular myocytes were isolated enzymatically from the hearts of 2-3-kg adult New Zealand white rabbits using standard
Dynamic restitution of the action potential during electrical alternans and ventricular fibrillation.
www.biophysj.org /cgi/content/full/77/6/2930   (5349 words)

 Quiz: Arrhythmias
Name a location where the ventricular action potential begins in third degree AV block.
Name the location where the ventricular action potential begins in second degree AV block.
Name the location where the ventricular action potential begins in first degree AV block.
courses.washington.edu /physeng/heart/arrhythmia.htm   (129 words)

 Genomics|HuGENet|Reviews|longQT syndrome|PubMed ID: 16540748
Among the various LQTS genotypes, the most common feature predisposing to arrhythmia is prolongation of the ventricular action potential duration during cardiac repolarization, measured as the QT interval on the electrocardiogram (Fig.
current during the plateau phase of the cardiac action potential, i.e., a loss-of-function of the ion channel.
The channel remains open longer, ventricular repolarization is delayed, and the QT interval is lengthened.
www.cdc.gov /genomics/hugenet/reviews/longQT.htm   (5111 words)

 Priebe-Beuckelmann Model of Human Ventricular Cardiac Action Potentials, 1998
This model is based on the Luo-Rudy II model of a guinea-pig ventricular myocyte with currents scaled to fit human cell data.
Abstract excerpt: " In the present study, selected ionic currents based on human data are incorporated into a model of the ventricular action potential for the purpose of studying the cellular electrophysiological consequences of heart failure.
Ionic currents that are not yet sufficiently characterized in human ventricular myocytes are adopted from the action potential model developed by Luo and Rudy (LR model)."
www.simulogic.com /products/models/PriebeBeuckelmannModel_1998.html   (138 words)

 Regulation of Deactivation by an Amino Terminal Domain in Human Ether-a-go-go¬†-related Gene Potassium Channels -- Wang ...
N-type inactivation in three respects: (a) deletion of the NH terminus slows C-type inactivation; (b) the action of the NH terminus is sensitive to elevated concentrations of external K
the repolarization phase of the cardiac action potential.
although the nature of this coordinate action remains to be elucidated.
www.jgp.org /cgi/content/full/112/5/637   (5892 words)

 Aborted sudden death in a young male -- 79 (937): 664 -- Postgraduate Medical Journal
Figure 1  Phases of the cardiac ventricular action potential; solid line shows normal ventricular action potential and dotted line shows Brugada-type action potential (schematic).
exclusively to the malignant ventricular arrhythmias that occur
action potential in some, but not all epicardial sites (schematically
pmj.bmjjournals.com /cgi/content/full/79/937/664   (1029 words)

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