Question

During the transmission of nerve impulse through a nerve, the potential on the inner side of the plasma membrane has which type of electric charge?

• 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

The correct option is D First negative, then positive and again back to negative

At the resting stage, the membrane potential is always negative (-70 mV). When the impulse is generated, the sodium channels are opened. The sodium ions rushes inside the cell. This causes the membrane potential to become positive. This is called as depolarisation. The region of positive charge causes nearby sodium channels to close and potassium channels to open. Potassium ions exit the axons and the membrane potential is brought back to negative (-30 mV). This is called as repolaristaion. And then the membrane potential comes back to the resting potential for the conduction of the next impulse.

So, the correct answer is option D.