Describe an action potential and explain why a region of the membrane that is in the absolute refractory period cannot experience another action potential until repolarization is complete. Include the following in your answer : voltage-gated Na+ channels, voltage-gated K+ channels, activation gate, inactivation gate, threshold voltage, increasing membrane potential, and decreasing membrane

Question

potential.

What will be an ideal response?

Answer 1

When a voltage-gated Na+ channel is at rest, its inactivation gate is open and its activation gate is closed. When threshold voltage is reached, the activation gate opens and allows Na+ ions to diffuse into the cell; this action decreases the membrane potential to the point that the potential becomes positive. At the peak of the depolarization event, the activation and inactivation gates in the Na+ channels close, but the voltage-gated K+ channels open. As K+ ions diffuse out of the cell, the membrane potential increases; i.e., the membrane repolarizes. The inactivation gate in the Na+ channels will remain shut until the membrane potential has been completely repolarized. After repolarization, the inactivation gate will reopen. Now the membrane can respond to another stimulus.