What happens to the membrane at site A when a stimulus is applied?

What happens to the membrane at site A when a stimulus is applied?
  1. The membrane becomes freely permeable to potassium ions (K⁺).
  2. The membrane becomes freely permeable to sodium ions (Na⁺).
  3. The membrane becomes impermeable to both sodium ions (Na⁺) and potassium ions (K⁺).
  4. The membrane becomes permeable to both sodium ions (Na⁺) and potassium ions (K⁺).

Solution

When a stimulus is applied at a site on the polarised membrane, the membrane at the site A becomes freely permeable to sodium ions (Na⁺), leading to an influx of Na⁺ and a reversal of the polarity at that site.

Asked in: NCERT

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