Neural Control and Coordination Question 19
19. During the transmission of nerve impulse through a nerve fibre, the potential on the inner side of the plasma membrane has which type of electric change?
[2007]
(a) First positive, then negative and continue to be positive
(b) First negative, then positive and continue to be positive.
(c) First positive, then negative and again back to positive
(d) First negative, then positive and again back to negative.
Show Answer
Answer : d
Hints & Solutions
(d) Once the events of depolarization have occurred, a nerve impulse or spike is initiated. Action potential is another name of nerve impulse. It lasts for about $1 msec$ (millisecond). The stimulalted, negatively charged point on the outside of the membrane sends out an electrical current to the positive point (still polarized adjacent to it). This local current causes the adjacent inner part of the membrane to reverse its potential from $-70 mV$ to $+30 mV$. The reversal repeats itself over and over until the nerve impulse is conducted through the length of the neuron.
