Question

What would happen to the SA node if a chemical blocker was used to reduce transport of Na+ into the pacemaker cells?

Answer 1

Sodium channel blocker mainly used as Antiarrhythmic drug.Sodium channet blocker depressant of SA node, because it play main major role in generation of action potential. sodium channel act on Phase0 of cardiac action potential.They are having main three classes

1)class IA : quinidine (prolong repolarization)increases ERP (effective refractory period)

2)class IB : Lidocaine (shorten repolarization)increaseERP

3) class IC : Flecainnide( little effect on repolarization) decreases ERP

SA node also called the pacemaker. Cardiac tissue have specialised properties like excitability, contractility, automatacity.

Normal sinus rhythm and heart rhythm is determine by SA node. Cardiac pacemaker cells spontaneously generate action potential. action potential spread through the conduction pathway. cardiac impulse start from SA node and goes to AV node. from AV node then this carries to Bundle of his and then Purkinje fibre of both side of heart. sodium channel blocker have membrane stabilizing activity i.e. inhibits the propagation of the action potential by blocking inward flow of sodium channel in cell.

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