Q.
Given is the diagrammatic representation of impulse conduction through an axon (at points A and B). View the diagram and arrange the steps of impulse conduction
I. The polarity of the membrane at site A is reversed and depolarized, $i.e.,$ the outer surface becomes negatively charged and the innerside becomes positively charged, generating nerve impulse II. A stimulus causes disturbance to the membrane at site of A nerve fibre resulting in leakage of $Na^{+}$ ions inside the nerve fibre III. 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. The impulse (action potential) generated at site A arrives at site B. The sequence is repeated along the length of the axon and consequently the impulse is conducted IV. Immediately ahead, the axon ($e.g.,$ 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 The correct option is
A) I $\rightarrow$ II $\rightarrow$ IV $\rightarrow$ III
B) II $\rightarrow$ I $\rightarrow$ III $\rightarrow$ IV
C) II $\rightarrow$ I $\rightarrow$ IV $\rightarrow$ III
D) I $\rightarrow$ IV $\rightarrow$ III $\rightarrow$ II
Explanation
II $\rightarrow$ I $\rightarrow$ IV $\rightarrow$ III
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.