Sodium pump stop operating during

Options

A. (a) Repolarization
B. (b) Action potential
C. (c) Resting potential
D. (d) None of the above

Answer

### Step-by-Step Solution:

1. **Understanding the Sodium Pump**: The sodium pump, also known as the sodium-potassium pump, is crucial for maintaining the resting membrane potential of neurons. It actively transports sodium ions out of the neuron and potassium ions into the neuron.

2. **Identifying the Phases of Action Potential**: The action potential consists of four main phases:
- **Resting Potential**: The neuron is at -70 mV, with the sodium and potassium channels closed.
- **Depolarization**: A stimulus causes sodium channels to open, allowing sodium ions to flow into the neuron, leading to a rise in membrane potential.
- **Action Potential**: This occurs when the membrane potential reaches around +30 mV, indicating maximum depolarization.
- **Repolarization**: Potassium channels open, allowing potassium ions to exit the neuron, which helps return the membrane potential back to resting levels.
- **Return to Resting Potential**: The neuron stabilizes back to -70 mV.

3. **Determining When the Sodium Pump Stops Operating**: The sodium pump primarily operates to maintain the resting potential and restore the ion balance after an action potential. During the action potential phase, when the sodium channels are open and sodium is rushing into the neuron, the sodium pump's activity is effectively halted because the focus is on the rapid influx of sodium ions.

4. **Conclusion**: The sodium pump stops operating during the **Action Potential** phase, specifically when the sodium channels are open and the neuron is depolarizing.

### Final Answer:
The sodium pump stops operating during the **Action Potential** phase.

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