Question

Given below is the diagrammatic representation of impulse conduction through an axon-


Select the option with the incorrect information about impulse conduction at point A and B.

• A. Polarity at the site – B is reversed and hence called repolarization.
• B. Action potential generated at site – A arrives site B
• C. An electric current flows on the inner surface from site A to B and on outer surface, from site B to A to complete the circuit
• D. This current promotes opening of channels at site B

Answer 1

The correct option is A Polarity at the site – B is reversed and hence called repolarization.

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, an action potential is generated at site A, which is carried forward towards the site B.
Thus, the impulse (action potential) generated at site A arrives at site B. This causes opening of channels at site B, resulting in influx of sodium ions causing depolarisation .This sequence is repeated along the length of the axon and consequently, the impulse is conducted.
So, the incorrect statement id- option d because depolarisation takes place instead of repolarisation.