Action potential is generated by

Options

A. `Na^(+)`
B. `K^(+)`
C. `Ca^(+)`
D. `Cl^(-)`

Answer

### Step-by-Step Solution:

1. **Understanding Action Potential**:
- Action potential is a rapid change in the electrical membrane potential of a neuron. It is crucial for the transmission of signals along nerve cells.

2. **Phases of Action Potential**:
- The action potential consists of three main phases: depolarization, repolarization, and hyperpolarization.

3. **Depolarization Phase**:
- The first phase is depolarization, which occurs when sodium (Na⁺) channels open. This allows sodium ions to flow into the neuron, causing the inside of the cell to become more positive (less negative). This shift in charge is what initiates the action potential.

4. **Repolarization Phase**:
- Following depolarization, the sodium channels close, and potassium (K⁺) channels open. Potassium ions flow out of the neuron, which helps to bring the membrane potential back down to a more negative value, thus repolarizing the cell.

5. **Hyperpolarization Phase**:
- Sometimes, the potassium channels remain open for a brief period, causing the membrane potential to become even more negative than the resting potential. This is known as hyperpolarization.

6. **Conclusion**:
- The generation of action potential is primarily due to the influx of sodium ions during depolarization. Therefore, the correct answer to the question "Action potential is generated by" is **sodium (Na⁺)**.