An action potential can be generated because some of the voltage gated K+ channels are available for opening

No action potentials can be generated because all of the voltage gated Na+ channel are inactive

An action potential can be generated because some of the voltage-gated Na+ channels are available for opening

No action potentials can be generated because all the Na+/K+ pumps are inactive

No action potentials can be generated because all the voltage gated K+ channels are inactive

All voltage-gated Na⁺ channels open.

Only half the number of voltage-gated Na⁺ channels in the membrane open.

Enough voltage-gated Na⁺ channels open to allow a second AP at the same threshold.

Enough voltage-gated Na⁺ channels open to allow a second AP at a threshold about 50% lower than prior to the first AP.

Voltage-gated Na⁺ channels begin to recover in a random stochastic process.