Now once action potential starts from the opening of the gated voltage Na⁺ channels the Na⁺ FLOWS in quickly because of the concentration gradient created by the Na/K pump AND due to the electrical potentail created (negative charge that is inside the nerve. This is the electrical pulse!

The Na⁺ channels open fast and close fast but gated K⁺ open slower and close slower. K⁺ voltage protein channels are made of different amino acids and thus require a greater depolarization to create a allosteric change in folded protein that will open pores for K⁺ to flow out!

Remember that as Na⁺ flows in, the charge of the inside of the nerve becomes less negative and this allows K⁺ to leave much easier.  K⁺ leaves through the permanent open channel proteins BUT voltage gated proteins that are at the axon hillock and beyond will open to speed up the loss of K⁺ out of the cell which helps the inside of the nerve to regain the resting potential.  The Na needs to pumped out by the Na/K pump while the K+ is pumped back in. This occurs in the refractory period.