Aneuron has a resting potential of about millivolts.
+50
+35
–55
–70
–80

A neuron has a resting potential of about -70 millivolts.  

The resting membrane potential is stable potential that each neuron has at rest and it is determined:  

•By concentration gradients of ions across the membrane  

•by membrane permeability to each type of ion (potassium, sodium, calcium, and chloride ions).

Voltage of neuron membrane is actually a difference in electric potential between positive and negative electric charges on opposite sides of a plasma membrane (inside of the cell is more negative than the outside). So, we say that the membrane is polarized.

If the membrane potential becomes more positive than it is at the resting potential, it becomes depolarized. Otherwise, it is hyperpolarized.