Know what the resting potential of a neuron is (-70 mV) More importantly, know that the inside of a neuron is negative relative to the outside. How did it get this way?
Nerve signal transmission begins when, upon stimulation, some protein channels open up, allowing a movement of positively charged sodium ions (Na+) into the cell. For a brief time, the interior of the cell becomes positively charged at this location. On either side of this location, however, the interior of the cell remains negatively charged. Attracted by this negative charge, the Na+ ions move laterally in both directions from their point of entry.