Question

Which of the following event occurs during the depolarization phase of an action potential in the neuronal membrane?

• A. ${\text{K}}^{\text{+}}$ ions rapidly move outside the cell
• B. ${\text{Na}}^{\text{+}}$ ions rapidly move inside the cell
• C. ${\text{Na}}^{\text{+}}$ ions rapidly move outside the cell
• D. ${\text{K}}^{\text{+}}$ ions rapidly move inside the cell

Answer 1

Answer: (B)

During depolarization, the voltage-gated ${\text{Na}}^{+}$ channel opens due to the arrival of signal or action potential. This leads to the rapid movement of ${\text{Na}}^{+}$ ions from an outside extracellular fluid (ECF) to inside axoplasm as the concentration of ${\text{Na}}^{+}$ ions is more on outside or ECF. This leads to developing a net positive charge inside and net positive charge outside the axonal membrane.