Question

An action potential in the nerve fibre is produced when positive and negative charges on outside and the inside of the axon membrane are reversed because

• A. More potassium ions enter the axon as compared to sodium ions leaving it
• B. More sodium ions enter the axon as compared to potassium ions leaving it
• C. All potassium ions leave the axon
• D. All sodium ions enter the axon

Answer 1

The correct option is B More sodium ions enter the axon as compared to potassium ions leaving it

When a nerve fibre is stimulated, its membrane becomes more permeable to sodium ions, hence, more sodium ions enter the axon than potassium ions leaving it. As a result, the positive and negative charges on the outside and inside of the membrane are reversed. The membrane with reversed polarity is called depolarised.