Sodium-potassium pump transports

Options

A. `Na^+ and K^+` out of the neuron
B. `Na^+ and K^+` into the neuron
C. `Na^+` into the neuron and `K^+` out of the neuron
D. `K^+` into the neuron and `Na^+` out of the neuron

Explanation

### Step-by-Step Solution:

1. **Understanding the Sodium-Potassium Pump**: The sodium-potassium pump is a type of active transport mechanism found in the cell membrane of neurons. It is crucial for maintaining the resting membrane potential and overall cellular homeostasis.

2. **Transport Mechanism**: The pump works by moving sodium (Na⁺) and potassium (K⁺) ions across the neuronal membrane. Specifically, for every three sodium ions that are transported out of the neuron, two potassium ions are transported into the neuron.

3. **Direction of Ion Movement**:
- **Sodium (Na⁺)**: The pump expels three sodium ions from the inside of the neuron to the outside.
- **Potassium (K⁺)**: The pump brings two potassium ions from the outside of the neuron into the inside.

4. **Conclusion**: Therefore, the sodium-potassium pump transports sodium ions out of the neuron and potassium ions into the neuron. This process is essential for maintaining the electrochemical gradient necessary for nerve impulse transmission.

5. **Final Answer**: The sodium-potassium pump transports potassium ions into the neuron and sodium ions out of the neuron.