Question

Which of the following statement characterizes the depolarized state of a neuron?

• A. $K^{+}$ outflow begins
• B. $K^{+}$ channels remain open
• C. $N{a}^{+}$ gets outside through channels
• D. $N{a}^{+}$ gets inside through ion channels

Answer 1

The correct option is D

$N{a}^{+}$ gets inside through ion channels

When a stimulus of adequate strength (threshold stimulus) is applied to a polarized membrane of a neuron, the permeability of the membrane to $N{a}^{+}$ is greatly increased. It is due to the fact that the $N{a}^{+}$ channels open and $K^{+}$ channels remain closed. As a result, $N{a}^{+}$ flows in by diffusion. Since more $N{a}^{+}$ enters the cell, the electrical potential of the membrane changes from - 70 mV to zero. At this potential, the membrane is called depolarized. The membrane now becomes less permeable to $N{a}^{+}$ and more permeable to $K^{+}$. $N{a}^{+}$ influx stops and $K^{+}$ outflow begins until the original resting state of ionic concentration is achieved. This is called repolarization of the membrane.