Many biological and synthetic pharmacological agents act by

Many biological and synthetic pharmacological agents act by specifically blocking certain types of ion channels. Indicate the effects on the waveform of an action potential by drugs that rapidly and irreversibly block (1) voltage-gated Na+ channels from opening, (2) voltage-gated K+ channels from opening, and (3) resting Na+ leak channels. (4) What about a drug that causes a ten-fold reduction of voltage-gated Na+ channel inactivation?

Solution

a)Blocking sodium channels reduces the velocity of action potential transmission within the heart.The principal effect of reducing the rate and magnitude of depolarization by blocking sodium channels is a decrease in conduction velocity in non-nodal tissue.Sodium-channel blockers may also alter the action potential duration (APD) and effective refractory period (ERP).Because some sodium-channel blockers increase the ERP (Class IA antiarrhythmic),while others decrease the ERP (Class IB) or have no effect on ERP (Class IC).
b)the cell will be unable to repolarise.
c)Leak channels are responsible for counteracting the drive for a negative charge,if those are blocked,then the charge will become more negative.
d)Slow inactivation plays an important role in controlling membrane excitability,firing properties,and spike frequency adaptation