Nerve firing master

Voltage differences in nerve cells are a result of pumping sodium ions out of the cell and potassium ions into the cell through the Na-K pump  Creates a neuron with a negatively charged interior relative to the exterior ~-70mV.

A stimulus causes a gate in the Na+ Channel to open  Since there is a high concentration of Na+ outside, Na+ diffuses into the neuron.  The electrical potential changes to +30 mV or more.

Depolarization causes the K+ Channel gate to immediately open.  K+ diffuses out of the neuron.  This reestablishes the initial electrical potential of ~-70 mV.

During this time (~ 1 msec), the Na+ and K+ Channels cannot be opened by a stimulus.  The Na+/K+ Pump actively pumps Na+ out of the neuron and K+ into the neuron.  This reestablishes the initial ion distribution of the resting neuron.