Question

During the conduction of nerve impulse, the action potential is the result of movement of

• A. N$a^{+}$ from intracellular fluid to extracellular fluid
• B. N$a^{+}$ from extracellular fluid to intracellular fluid
• C. N$a^{+}$ towards both directions
• D. None of the above

Answer 1

The correct option is B N$a^{+}$ from extracellular fluid to intracellular fluid

The polarised neuron is less permeable to the Na${}^{+}$ ions as compared to the K${}^{+}$ when at rest due to the activity of the Na${}^{+}$-K${}^{+}$ pumps. The arrival of the threshold stimulus activates the voltage-gated Na${}^{+}$ channels due to which the Na${}^{+}$ ions move from the extracellular fluid to the intracellular fluid of the axon. This causes depolarization of the membrane and the impulse is generated. This impulse moves down the axon in the similar depolarization wave.

Hence, the correct answer is 'Na${}^{+}$ from extracellular fluid to intracellular fluid'