Question

When a stimulus is applied at a site on the polarised membrane:

• A. $N{a}^{+}$ moves out of axoplasm
• B. $N{a}^{+}$ moves into axoplasm
• C. $K^{+}$ moves into axoplasm
• D. $C{a}^{2+}$ moves into axoplasm

Answer 1

The correct option is B $N{a}^{+}$ moves into axoplasm

When a stimulus is applied at a site on the polarised membrane, the membrane at the site becomes freely permeable to $N{a}^{+}$. This leads to opening of $N{a}^{+}$ channels and results in a rapid influx of $N{a}^{+}$ into the axoplasm followed by the reversal of the polarity at that site called a depolarized state.