(c) Conduction of a nerve impulse along a nerve fibre
A nerve impulse is conducted across the length of a nerve fibre in an organised manner.
On the nerve fibre during the conduction of an impulse, a region is always depolarised and a region next to it will be polarised. To send the impulse forward, the depolarised region repolarises and the polarised region depolarises. This is repeated across the length of the nerve fibre which helps in the conduction of impulse.
It occurs in following steps:
At a depolarised region, consider site A, there will be positive charge on the inner surface of the membrane and negative charge on the outer surface of the membrane.
The region next to it which is polarised, consider site B, there will B positive charge on the outer surface of the membrane and negative charge on the inner surface of the membrane.
Hence, at site A, the current will flow on the inner surface of the membrane from A to B, and at site B, the current will flow on the outer surface from B to A. This will complete the circuit of the current flow.
This will help site B to depolarise, so that the impulse is conducted to site B.
As soon as the impulse is conducted to site B, site A will get repolarised.
When site B will be in the depolarised state, the region next to it, consider site C, will be polarised.