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

Options

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

Explanation

**Step-by-Step Solution:**

1. **Understanding Resting Membrane Potential:**
- At rest, a neuron has a resting membrane potential of approximately -70 mV. This means that the inside of the neuron is negatively charged compared to the outside. This difference in charge is due to the distribution of ions, primarily potassium (K+) and sodium (Na+).

2. **Ion Distribution:**
- Inside the neuron (intracellular fluid), there is a higher concentration of K+ ions and negatively charged proteins. Outside the neuron (extracellular fluid), there is a higher concentration of Na+ ions.

3. **Stimulus Arrival:**
- When a stimulus is applied to the neuron, it causes the sodium channels in the membrane to open. This is a crucial step in the generation of an action potential.

4. **Movement of Sodium Ions:**
- Due to the concentration gradient, sodium ions (Na+) rush into the neuron from the extracellular fluid where they are in higher concentration. This influx of Na+ ions causes the inside of the neuron to become more positively charged, leading to depolarization.

5. **Generation of Action Potential:**
- The rapid influx of Na+ ions changes the membrane potential from -70 mV to a positive value (approximately +30 mV). This change in potential is known as the action potential, which propagates along the axon as a nerve impulse.

6. **Conclusion:**
- Therefore, during the propagation of a nerve impulse, the action potential results from the movement of sodium ions (Na+) from the extracellular fluid into the intracellular fluid.

**Final Answer:**
The action potential results from the movement of sodium ions (Na+) from the extracellular fluid into the intracellular fluid.

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