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

Options

A. `K^+`ions from intracellular fluid to extracellular fluid
B. `Na^(+)` ions from extracellular fluid to intra cellular fluid
C. `K^+ ` ions from extracellular fluid to intra cellular fluid
D. `Na^+` ions from intracellular fluid to extra cellular fluid

Answer

**Step-by-Step Solution:**

1. **Understanding Action Potential:**
- Action potential is a rapid change in the electrical potential across a neuron's membrane, which is essential for the propagation of nerve impulses.

2. **Role of Ion Movement:**
- The generation of action potential is primarily due to the movement of ions, specifically sodium (Na⁺) and potassium (K⁺) ions, across the neuron's membrane.

3. **Voltage-Gated Channels:**
- The neuron's plasma membrane contains voltage-gated ion channels that open in response to changes in membrane potential.
- Sodium channels open when the membrane potential reaches a threshold, allowing Na⁺ ions to flow into the neuron.

4. **Influx of Sodium Ions:**
- Sodium ions (Na⁺) are predominantly found in the extracellular fluid. When the sodium channels open, Na⁺ ions move from the extracellular fluid into the intracellular fluid, leading to depolarization of the membrane.

5. **Depolarization:**
- The influx of Na⁺ ions causes the inside of the neuron to become more positively charged compared to the outside, which is the key characteristic of action potential.

6. **Conclusion:**
- Based on the movement of ions during the action potential, the correct answer to the question is that action potential results from the movement of Na⁺ ions from the extracellular fluid to the intracellular fluid.

**Final Answer:**
- The action potential results from the movement of Na⁺ ions from extracellular fluid to intracellular fluid (Option B).

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