One of the following ions are required for nerve impulse transmission at the neuro-muscular junction :

Options

A. Magnesium
B. Chloride
C. Calcium
D. Iron

Answer

To solve the question regarding which ion is required for nerve impulse transmission at the neuromuscular junction, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Context**: The question asks about the ions involved in nerve impulse transmission specifically at the neuromuscular junction, which is the connection between nerves and muscles.

2. **Evaluate the Options**:
- **Option 1: Magnesium**: While magnesium plays a role in muscle contraction, it is not directly involved in the transmission of nerve impulses at the neuromuscular junction.
- **Option 2: Chloride**: Chloride is important for maintaining blood volume and pressure, but it does not play a direct role in nerve impulse transmission at the neuromuscular junction.
- **Option 3: Calcium**: Calcium ions are crucial for the release of neurotransmitters at the neuromuscular junction. When a nerve impulse reaches the end of a motor neuron, calcium ions enter the neuron, triggering the release of acetylcholine, which transmits the signal to the muscle.
- **Option 4: Iron**: Iron is essential for various bodily functions, including oxygen transport, but it is not involved in nerve impulse transmission.

3. **Identify the Correct Answer**: Based on the evaluation, the ion required for nerve impulse transmission at the neuromuscular junction is **Calcium** (Option 3).

### Final Answer:
The correct answer is **Calcium**.