NEET 2007 Biology question

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 charge?

(1)First positive, then negative and again back to positive
(2)First negative, then positive and again back to negativeCorrect
(3)First positive, then negative and continue to be negative
(4)First negative, then positive and continue to be positive.

Answer: (2)

Solution

In a resting (polarised) neuron the inner side of the axolemma is negative with respect to the outer side (about -70 mV) because of the Na+/K+ pump and greater K+ permeability. When a stimulus arrives, Na+ channels open and Na+ rushes in, so the inside becomes positive (depolarisation, about +30 mV). Immediately K+

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Question ID VK-089795