As a result the outer surface of axonal membrane is positively charged and inner surface is negatively charged. The electric potential difference across the resting plasma membrane is called resting potential.
Action Potential: When a nerve fibre is stimulated, the permeability of membrane to Na+ is greatly increased at the point of stimulus (rapid influx of Na+) and hence polarity of membrane is reversed and now membrane is said to be depolarised. The electric potential difference across the plasma membrane at that site is called action potential, which infact termed as nerve impulse. Depolarisation is very rapid, so that conduction of nerve impulse along the entire length of axon occurs in fractions of second.
