Role of Sodium Ions in Action Potential — NEET Biology
📚 Practice ConceptExplain the role of Na+ in the generation of action potential.
Assertion (A): Action potential generation involves polarity reversal at the stimulated site. Reason (R): Stimulus makes the membrane freely permeable to Na+, leading to rapid Na+ influx and reversal of polarity.
View solution & NCERT explanation
Correct answer: A — If both assertion and reason are true and the reason is the correct explanation of the assertion.
NCERT states “When a stimulus is applied at a site on the polarised membrane, the membrane at the site becomes freely permeable to Na+. This leads to a rapid influx of Na+ followed by the reversal of the polarity at that site.” Both statements are true. The Reason explains the mechanism (Na+ permeability increase → Na+ influx) that causes the polarity reversal described in the Assertion.
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Through deep analysis of NEET and NTA, 176 of the 180 ReNEET 2026 (June 21) questions were already in the MedicNEET question bank before the exam.
176/180MedicNEET's Biology question bank is built from the same NCERT lines NTA picks repeatedly. Not random MCQs — questions crafted exactly like NTA crafts them.