Consider site A to be the site of excitation and hence depolarised. At sites immediately ahead, the axon (eg: site B) membrane has a .positive charge on the outer surface and a negative charge on its inner surface. As a result, a current flows on the inner surface from site A to site B. On
the outer surface current flows from site B to site A to complete the circuit of current flow. Hence, the polarity at the site is reversed, and an action potential is generated at site B. Thus, the impulse generated at site A arrives at site B. The sequence is repeated along the length of the axon and consequently the impulse is conducted.
