In a neuron at rest, the concentration of __________ is higher outside the cell than in the cell, whereas the concentration of _________ is greater inside the cell than outside.

• A. Sodium; potassium.
• B. Potassium; sodium.

Answer: (A)

Verified step by step guidance

1. Understand the concept of resting membrane potential in neurons. At rest, neurons maintain a specific distribution of ions across their membrane, which is crucial for their function.
2. Identify the key ions involved in establishing the resting membrane potential: sodium (Na⁺) and potassium (K⁺). These ions have different concentrations inside and outside the neuron.
3. Recall that the sodium-potassium pump actively transports ions to maintain concentration gradients. It pumps sodium ions out of the cell and potassium ions into the cell.
4. Recognize that at rest, the concentration of sodium ions (Na⁺) is higher outside the neuron than inside, while the concentration of potassium ions (K⁺) is higher inside the neuron than outside.
5. Use this understanding to fill in the blanks: Sodium concentration is higher outside the cell, and potassium concentration is higher inside the cell.