What type of action potential is seen in the SA node?
The SA nodal cells have an unstable resting membrane potential that spontaneously depolarizes due to a pacemaker potential. This is caused by the “funny” Na+ current and a decrease in the conductance of the inward rectifier K+ channel.
What is the main difference between Class 1A and Class 1c antiarrhythmic drugs?
Class Ic drugs are more potent antiarrhythmics than either class Ia or class Ib drugs. Class Ic drugs do not block potassium channels directly. Class Ic drugs may organize and slow atrial tachyarrhythmias enough to permit 1:1 AV conduction with marked acceleration of the ventricular response rate.
What are Class 1 antiarrhythmics used for?
Class Ia antiarrhythmic drugs Class Ia drugs block repolarizing potassium channels, prolonging the refractory periods of fast-channel tissues. On the ECG, this effect is reflected as QT-interval prolongation even at normal rates. . The primary indications are supraventricular and ventricular tachycardias.
Why SA node is known as the pacemaker of heart Class 10?
Why S.A. node is called pacemaker of heart? The SA node or sino-atrial node (SAN) is called the the natural pacemaker of the heart. It controls the heart rate by generating electrical impulses and then sending electrical signals through the heart muscle, causing the heart to contract and pump blood throughout the body.
How does the SA node generate an action potential?
When a channel is opened, there is increased electrical conductance (g) of specific ions through that ion channel. As ions flow through open channels, they generate electrical currents that change the membrane potential. In the SA node, three ions are particularly important in generating the pacemaker action potential.
What are Class III antiarrhythmic drugs?
Amiodarone, sotalol, dofetilide, and ibutilide are examples of class III drugs that are currently available. Amiodarone and sotalol have other antiarrhythmic properties in addition to pure class III action, which differentiates them from the others. However, all have potential serious adverse events.
What is a class V antiarrhythmic?
Class 5 antiarrhythmic drugs are a miscellaneous group of medications that do not belong to a traditional class of antiarrhythmics. These drugs have varied mechanisms of action and uses. The medications in this class are digoxin, adenosine, Mg sulfate, and atropine.
What are Class 3 antiarrhythmics used for?
Class III antiarrhythmic drugs act by blocking repolarising currents and thereby prolong the effective refractory period of the myocardium. This is believed to facilitate termination of re-entry tachyarrhythmias. This class of drugs is developed for treatment of both supraventricular and ventricular arrhythmias.
What is a Class 1C drug?
Class 1C antiarrhythmic drugs (AADs) are effective first‐line agents for atrial fibrillation (AF) treatment. However, these agents commonly are avoided in patients with known coronary artery disease (CAD), due to known increased risk in the postmyocardial infarction population.
How does the SASA node generate cardiac action potential?
SA node generates cardiac action potential due to spontaneous depolarization by the pace maker cells with the help of auto rhythmic fibers which results in setting the basic pace for the heart rate, and this is conducted through both atria.
What is the function of the SA node and AV node?
AV node involves the reception of the action potential from the SA node and passes it to the AV bundle. The action of the SA node is regulated by autonomic nervous system. The action of the AV node is regulated by SA node. SA node acts as a pacemaker.
What causes the AV node to generate action potentials?
This causes the AV node to generate action potentials at a rate similar to SA node. Upon cessation of high frequency impulses from SA node, as happens during bundle blocks, the AV node is shown to beat at its own inherent frequency. Impulse generation of purkinje fibers is at a rate of 15-30 beats/min.
What is the mechanism of action potential in SA nodal cells?
Unlike non-pacemaker action potentials in the heart, and most other cells that elicit action potentials (e.g., nerve cells, muscle cells), the depolarizing current is carried into the cell primarily by relatively slow Ca ++ currents instead of by fast Na + currents. There are, in fact, no fast Na + channels and currents operating in SA nodal cells.