What is the expected effect on nerve impulse transmission if extracellular sodium were acutely lowered in a neuron while intracellular potassium remained unchanged?

• A. Reduced ability to generate action potentials because the reduced extracellular sodium decreases the inward sodium current during depolarization, slowing nerve impulse transmission.
• B. Complete and irreversible block of all nerve activity immediately because sodium is the only ion that supports any electrical signal in neurons and muscle tissue.
• C. No change in nerve conduction because potassium is the main ion responsible for depolarization and sodium levels do not influence neuronal electrical activity.
• D. Increased frequency of action potentials because lower extracellular sodium makes the membrane more excitable and more likely to depolarize spontaneously.

Answer: (A)