Opening of the Inactivation Gate of the Na Channel

Question

Opening of the inactivation gate of the Na channel
A) Causes the upstroke of the action potential
B) Occurs during depolarization to threshold
C) Occurs after repolarization of the membrane
D) Is blocked by tetrodotoxin
E) Is blocked by TEA

Accepted Answer

The inactivation gate of the Na channel closes (or inactivates) after the membrane has depolarized and the action potential has peaked, leading into the repolarization phase. This process occurs after the membrane has been depolarized, not during the upstroke of the action potential or its initiation. Tetrodotoxin blocks the pore of the Na channel, not specifically the inactivation gate, and TEA is known to block K channels, not Na channels.