Resting membrane potential is maintained by

Options

A. hormones
B. neurotransmitters
C. ion pumps
D. none of the above

Answer

### Step-by-Step Solution:

1. **Understanding Resting Membrane Potential**:
- The resting membrane potential is the electrical potential difference across the neuronal membrane when the neuron is not actively transmitting signals. It is typically around -70 millivolts (mV).

2. **Role of Ion Channels**:
- The membrane contains various types of ion channels. Among these, there are leak channels that remain open and allow ions to move across the membrane freely, and gated channels that open in response to specific stimuli.

3. **Leak Channels**:
- Leak channels primarily allow potassium ions (K+) to move out of the neuron, which contributes to the negative charge inside the cell. This movement of K+ ions is crucial for maintaining the resting membrane potential.

4. **Gated Channels**:
- Gated channels, on the other hand, are closed at rest and open only when a stimulus is received. When these channels open, sodium ions (Na+) can enter the cell, which depolarizes the membrane potential.

5. **Ion Pumps**:
- The sodium-potassium pump (Na+/K+ pump) is a critical ion pump that helps maintain the resting membrane potential. It actively transports 3 sodium ions out of the cell and 2 potassium ions into the cell, which helps restore and maintain the -70 mV potential after depolarization.

6. **Conclusion**:
- Therefore, the resting membrane potential is maintained primarily by ion pumps, specifically the sodium-potassium pump, which regulates the concentrations of sodium and potassium ions across the membrane.

### Final Answer:
The resting membrane potential is maintained by **ion pumps**.

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