Question

During the propagation of a nerve impulse, the action potential results from the movement of

• A. Sodium ions from ECF to ICF
• B. Sodium ions from ICF to ECF
• C. Potassium ions from ECF to ICF
• D. Potassium ions from ICF to ECF

Hint:

Action potential = depolarization due to \textbf{influx of Na$^+$ ions} into the neuron.

Answer 1

The Correct Option is A

Step 1: At rest, a neuron has a resting potential due to unequal distribution of ions across the membrane.
Step 2: When a nerve impulse is initiated, voltage-gated sodium channels open.
Step 3: Sodium ions ($\text{Na}^+$) move rapidly from the extracellular fluid (ECF) into the intracellular fluid (ICF).
Step 4: This inward movement of sodium ions causes depolarization of the membrane, resulting in the action potential.