Depolarisation of neuron is caused due to
1) Opening of K + leak channels
2) Opening of voltage gated K + channels
3) Opening of voltage gated N a + channels
4) Both (2) & (3)

Options

A. Opening of `K^+` leak channels
B. Opening of voltage gated `K^+` channels
C. Opening of voltage gated `Na^+` channels
D. Both (2) & (3)

Answer

To solve the question regarding the cause of depolarization in a neuron, we can break it down step by step:

### Step-by-Step Solution:

1. **Understanding Neuron Resting Potential**:
- Neurons have a resting membrane potential where the inside of the neuron is negatively charged compared to the outside. This is primarily due to the distribution of ions, particularly sodium (Na⁺) and potassium (K⁺).

**Hint**: Remember that the resting state of a neuron is characterized by a negative internal charge.

2. **Triggering Depolarization**:
- When a neuron is stimulated, it undergoes depolarization, which is a change in the membrane potential from negative to positive. This is crucial for the transmission of nerve impulses.

**Hint**: Think about what happens when a neuron is activated or stimulated.

3. **Role of Sodium Channels**:
- Depolarization occurs primarily due to the opening of voltage-gated sodium (Na⁺) channels. When these channels open, sodium ions rush into the neuron, causing the inside of the cell to become more positive.

**Hint**: Focus on which ions are moving into the neuron during depolarization.

4. **Exclusion of Other Channels**:
- The opening of potassium (K⁺) channels (both leak and voltage-gated) typically leads to repolarization (returning to resting potential) rather than depolarization. Therefore, options involving K⁺ channels do not contribute to depolarization.

**Hint**: Consider the function of K⁺ channels in the context of action potentials.

5. **Final Answer**:
- Based on the above analysis, the correct answer to the question is **3) Opening of voltage-gated Na⁺ channels**. The other options (1 and 2) do not contribute to depolarization.

### Conclusion:
The depolarization of a neuron is primarily caused by the opening of voltage-gated sodium channels, allowing Na⁺ ions to flow into the neuron, leading to a positive shift in membrane potential.