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Topic: Cardiac action potential

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In the News (Tue 18 Jun 19)

  Human diseases info cardiovascular health respiratory renal onlogy metabolic endocrinediseases
When the membrane potential is depolarized to a certain threshold level, an action potential occurs with a rapid upstroke (phase 0); a return toward zero from the initial overshoot or early rapid repolarization (phase 1); a plateau (phase 2); final rapid repolarization (phase 3); and resting membrane potential and ” diastolic depolarization (phase 4).
Action potentials recorded from different tissues in the heart remounted with a His bundle recording and scalar ECG from a patient to illustrate the timing during a single cardiac cycle.
Refractoriness is a property of cardiac tissue during which a stimulus occurring soon after a previous action potential fails to elicit another normal action potential; it is most closely related to the duration of phase 3 of the cardiac action potential in most tissues.
www.humandiseaseinfo.com   (635 words)

 Molecular Biology of Sodium Channels and Their Role in Cardiac Arrhythmias
This prolongs the action potential duration and the QT interval on the ECG.
Marked prolongation of the action potential alters the voltage-time trajectory of the action potential such that repetitive depolarizations occur at the level of the action potential plateau.
The cardiac sodium channel is a complex multimeric protein consisting of an a subunit and a regulatory b1 subunit.
www.americanheart.org /presenter.jhtml?identifier=3000452   (2863 words)

  Action potential at AllExperts
Action potentials can be created by many types of cells, but are used most extensively by the nervous system for communication between neurons and to transmit information from neurons to other body tissues such as muscles and glands.
Action potentials are largely dictated by the interplay between sodium and potassium ions (although there are minor contributions from other ions such as calcium and chloride), and are often modeled using hypothetical cells containing only two transmembrane ion channels (a voltage-gated sodium channel and a non-voltage-gated potassium channel).
Action potentials are only regenerated at the unmyelinated nodes of Ranvier which are spaced intermittently between myelinated segments.
en.allexperts.com /e/a/ac/action_potential.htm   (3542 words)

  Science Fair Projects - Cardiac action potential
The resting membrane potential is the difference in ionic charge across the membrane of the cell during phase 4 of the action potential.
This phase of the action potential is associated with diastole of the chamber of the heart.
Phase 2 of the action potential corresponds to the ST segment of the ECG.
www.all-science-fair-projects.com /science_fair_projects_encyclopedia/Cardiac_action_potential   (1210 words)

 Reference.com/Encyclopedia/Cardiac action potential
The cardiac action potential is a specialized action potential in the heart, with unique properties necessary for function of the electrical conduction system of the heart.
The resting membrane potential is caused by the difference in ionic concentrations and conductances across the membrane of the cell during phase 4 of the action potential.
Once the cell is electrically stimulated (typically by an electric current from an adjacent cell), it begins a sequence of actions involving the influx and efflux of multiple cations and anions that together produce the action potential of the cell, propagating the electrical stimulation to the cells that lie adjacent to it.
www.reference.com /browse/wiki/Cardiac_action_potential   (1525 words)

 Citations: A Model of the Ventricular Cardiac Action Potential - Luo, Rudy (ResearchIndex)
A model of the ventricular cardiac action potential.
The action potential on Figure 2.3 was calculated using this model.
Luo, C. and Rudy, Y. A model of the ventricular cardiac action potential.
citeseer.ist.psu.edu /context/684209/0   (1157 words)

 Action potential Summary
An action potential represents a change in electrical potential from the resting potential of the neuronal cell membrane, and is a series of electrical and underlying chemical changes that travel down the length of a neural cell (neuron).
The standing potential is maintained because, although there are both electrical and concentration gradients (a range of high to low concentration) that induce the excess sodium ions to attempt to try to enter the cell, the channels for passage are closed and the membrane remains almost impermeable to sodium ion passage in the rest state.
It is at the synapse that the message carried by the action potential is passed to the next cell by neurotransmitters released by the action potential.
www.bookrags.com /Action_potential   (5382 words)

 Cardiac Pacemaker - Medgadget Wiki
Although all of the heart's cells possess the ability to generate these electrical impulses (or action potentials), a specialised portion of the heart, called the sinoatrial node, is responsible for the whole heart's beat.
The action potential generated by the SA node, passes down the cardiac conduction system, and arrives before the other cells have had a chance to generate their own spontaneous action potential.
As in all other cells, the resting potential of a pacemaker cell (-60mV to -70mV) is caused by a continuous outflow or "leak" of potassium ions through ion channel proteins in the membrane that surrounds the cells.
www.medgadget.com /wiki/wiki/Cardiac_Pacemaker   (939 words)

 BioMedical Engineering OnLine | Full text | Dispersion of cardiac action potential duration and the initiation of ...
Cardiac disease remains an important cause of sudden death in the industrialised world, and in many cases the lethal events are the cardiac arrhythmias called ventricular tachycardia (VT) and ventricular fibrillation (VF).
Action potentials were initiated in each virtual tissue by holding the membrane voltage along one edge at 0 mV for 2 ms.
Block of an action potential occurs if there is insufficient Na current to support a propagating wavefront [27]; when Na channels have not recovered from inactivation, then a propagating wave blocks and dissipates [28].
www.biomedical-engineering-online.com /content/4/1/11   (5569 words)

 lab 12
The pacemaker potential is initiated by a slow influx of Na and reduced efflux of K. This causes Ca channels to open, reversing the membrane potential, and rapid depolarization results.
The action potential created by these cells is propagated on to the other cells of the heart via gap junctions.
Cardiac Output: The cardiac output of the heart is the measurement of the amount of blood pumped perunit of time- usually measured by the minute.
www.humboldt.edu /~lls9/lab12.html   (1038 words)

 5-HT3 Receptor Antagonists and ECG Effects
The cardiac action potential, the basic unit of electrical activity in the heart, produces cardiac contractions.
Cardiac myocytes, like other types of muscle cells, have a negative potential difference (-90 mV) at rest between the cell membrane and extra-cellular space (ie, they are polarized).
If the action potential is prolonged during the repolarization phase, the membrane potential may abruptly reverse course and depolarize instead.
www.clevelandclinicmeded.com /medical_info/pharmacy/novdec2002/5ht.htm   (1656 words)

 Lecture L-I.16, quiz 1
the plateau phase of the cardiac action potential.
the rapid upstroke of the cardiac action potential.
Sodium influx is responsible for the peak of the action potential.
physio1.utmem.edu /~thomason/medphys_Int/quiz1.html   (102 words)

 Normal impulse conduction
The action potentials generated by the SA node spread throughout the atria primarily by cell-to-cell conduction.
Sympathetic activation increases conduction velocity in nodal and non-nodal tissues by increasing the slope of phase 0 of the action potentials.
Parasympathetic (vagal) activation decreases conduction velocity (negative dromotropy) in nodal and non-nodal tissues by decreasing the slope of phase 0 of the action potentials.
cvphysiology.com /Arrhythmias/A003.htm   (775 words)

Nerves of the autonomic branch of the nervous system lead to both smooth and cardiac muscle, but their effect is one of moderating the rate and/or strength of contraction.
Nerve impulses (action potentials) traveling down the motor neurons of the sensory-somatic branch of the nervous system cause the skeletal muscle fibers at which they terminate to contract.
The action potential that drives contraction of the heart passes from fiber to fiber through gap junctions.
users.rcn.com /jkimball.ma.ultranet/BiologyPages/M/Muscles.html   (3337 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)

Contrast the duration of the action potential and the refractory period in a cardiac muscle, a skeletal muscle, and a nerve.
Sketch the temporal relationship between an action potential in a cardiac muscle cell and the resulting contraction (twitch) of that cell.
Outline the sequence of events that occurs between the initiation of an action potential in a cardiac muscle cell and the resulting contraction and then relaxation of that cell.
www.the-aps.org /education/MedPhysObj/cardio.htm   (3429 words)

 Introduction: Understanding Action Potential
The action potential is brought on by a rapid change in membrane permeability to certain ions.
Once this occurs, many more sodium channels are open and the membrane potential begins rising more rapidly (rising phase) until it reaches the peak of the action potential.
Thus, the action potential of the cell is the change in voltage of the membrane potential that causes it to go from its negative resting state to a positive value for a very brief time.
library.thinkquest.org /C003758/Function/UnderstandingActionPotential.htm   (505 words)

 Cardiac Action Potential   (Site not responding. Last check: )
At onset of the action potential, there is a decrease in the permeability to Potassium, thus repolarisation takes longer to start.
Like all other excitable tissues, cardiac muscle is refractory to re-stimulation during the action potential.
But as the action potential of cardiac muscle lasts almost as long as the contraction itself, the refractory period is almost as long as the contraction period - 0.25 to 0.3 secs (in the ventricles)
www.biotech.um.edu.mt /home_pages/chris/Basic%20Physiology/Basichtml/Heart3.htm   (147 words)

 Action potential modulation of connexin40 gap junctional conductance -- Lin and Veenstra 286 (5): H1726 -- AJP - Heart ...
A maximum of four and an average of two 150-pS channels were initially open with an average of one channel closing during the action potential and remaining closed until final repolarization began during the cardiac action potential.
to the peak of the cardiac action potential.
Action potential conduction between guinea pig ventricular cells can be modulated by calcium current.
ajpheart.physiology.org /cgi/content/full/286/5/H1726   (4504 words)

 Phases of the cardiac action potential   (Site not responding. Last check: )
The upstroke of the cardiac action potential in atrial and ventricular muscle and His-Purkinje fibers is due to the sudden increase in membrane conductance to Na+.
Under normal conditions, the membrane potential of atrial and ventricular muscle cells remains steady throughout diastole.
I_K1 is the current responsible for maintaining the resting potential near the K+ equilibrium potential in atrial, AV nodal, His-Purkinje, and ventricular cells.
www.cyberecg.com /CyberECG/ECGKb/ECGKB_eng/Enc00074.html   (256 words)

 In the cardiac action potential
In skeletal muscle the action potential (AP) duration is about 2 ms and is over long before the peak of the twitch.
The twitch, being a very transient rise and fall of force, is over too quickly to allow full transmission to the tendon (the series elastic component of the muscle is not fully extended by the twitch).
The muscle twitch is of almost the same duration as the action potential, and since the refractory period extends beyond the end of the AP, the muscle cannot readily be tetanised.
www.mona.uwi.edu /fpas/courses/physiology/muscles/Cardiac_action_potential.htm   (308 words)

 Cardiac Action Potential ADAM   (Site not responding. Last check: )
Action potentials generated by autorhythmic cells (SA node) create waves of depolarization that spread to contractile cells via gap junctions.
• Calcium influx produces the rapidly rising phase of the action potential (depolarization), which results in the reversal of membrane potential from negative to positive inside the cell.
• The cardiac contractile cell relies on the autorhythmic cell to generate an action potential and pass the impulse down the line before the cell can contract.
www.accd.edu /pac/science/Hopper/Biol2402/Unit2/02CVAP5R.html   (725 words)

 physiology cardiac action potential (physiology cardiac action potetial) information.   (Site not responding. Last check: )
The cardiac action potential is much longer than that of skeletal muscle,..
When an action potential reaches the axon terminal, hundreds of these..
A model of the ventricular cardiac action potential.
www.tssgh.com /p/physiology_cardiac_action_potential.html   (136 words)

 cardiac action potential pictures (cardiac action potetial pictures) information.
cardiac action potential pictures (cardiac action potetial pictures) information.
Cardiac action potential Use active cursors to locate the CAPs and then..
allowing surface action potentials to be transported quickly to the inside of..
www.tssgh.com /c/cardiac_action_potential_pictures.html   (156 words)

 Amiodarone - Drugs Store - drugsstore.org
Amiodarone is categorized as a class III antiarrhythmic agent, and prolongs phase 3 of the cardiac action potential.
Amiodarone shows beta blocker-like and calcium channel blocker-like actions on the SA and AV nodes, increases the refractory period via sodium- and potassium-channel effects, and slows intra-cardiac conduction of the cardiac action potential, via sodium-channel effects.
However, because of the wide spectrum of the mechanism of action of amiodarone and the numerous side effects possible, there are a number of groups for which care should be taken when administering the drug.
www.drugsstore.org /amiodarone.html   (1677 words)

 Cardiac Action Potential And Ecg   (Site not responding. Last check: )
this worksheet), cardiac cardiac electrocardiogram of ekg or ecg is one of the most basic tests...
the duration of cardiac action potential and early and late...
Cardiac action potential, electrocardiogram (ECG), and long QT syndrome (LQTS).
www.boycottdelta.com /ecg-machines/cardiac-action-potential-and-ecg.html   (304 words)

 Cardiac Rhythm Disorders
Phases of the cardiac action potential and ionic and electrophysiological changes are associated with normal cardiac rhythm
-inward current-mediated action potentials are normal for the specialized conducting SA nodal and AV nodal tissues, which have resting membrane potentials in the -50 to-70 mV range.
Although for a given arrhythmia in a patient the mechanism may not be known, there are certain general explanations for the action of anti-arrhythmic agents.
www.pharmacology2000.com /Cardio/antiarr/antiarrtable.htm   (4629 words)

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