Question

During the transmission of nerve impulse through a nerve fibre, the inner membrane charge of the neurilemma will be

• A. first positive, then negative and continue to be negative.
• 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.

Answer 1

Answer: (D)

The electrical potential difference across the plasma membrane of a neuron is called the action potential or a nerve impulse. At the resting stage, the outer membrane is positively charged and the inner membrane is negatively charged. Upon stimulus, the membrane becomes freely permeable to Na+. This leads to a rapid influx of Na+ followed by the reversal of the polarity at that site, i.e., the outer surface of the membrane becomes negatively charged and the inner side becomes positively charged. Later repolarization happens to get back the inner membrane to negatively charged.