JAMB Biology 2021 Paper

Concept:The action potential of nervous transmission is driven by the movement of sodium and potassium ions across the neuron membrane.Explanation:At rest, the neuron membrane is polarized, mainly maintained by the $\mathrm{Na}^+/ \mathrm{K}^+$ pump.When a stimulus arrives, voltage-gated $\mathrm{Na}^+$ channels open first.Sodium ions, $\mathrm{Na}^+$, rush into the neuron, causing depolarization.Then voltage-gated $\mathrm{K}^+$ channels open, and potassium ions, $\mathrm{K}^+$, move out of the neuron.This outflow restores the negative charge inside the cell, a process called repolarization.The rapid changes in membrane potential created by these two ions form the action potential.Cations like $\mathrm{Fe}^{2+}$ and $\mathrm{Mg}^{2+}$ do not directly generate nervous impulses.Answer:C. $\mathrm{Na}^+$ and $\mathrm{K}^+$