Question

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

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