Define the following
Neurotransmitter

Explanation

**Step-by-Step Text Solution:**

1. **Definition of Neurotransmitter**: A neurotransmitter is defined as a chemical messenger in the nervous system.

2. **Function**: The primary function of neurotransmitters is to transmit signals between neurons. They carry messages from one neuron to another or from a neuron to other types of cells, such as muscle cells or gland cells.

3. **Examples**: Two well-known examples of neurotransmitters are:
- **Acetylcholine**: This neurotransmitter plays a critical role in muscle activation and various functions in the brain.
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