Which of the following is released by parasympathtic nervous system?

Options

A. Serotonin
B. Acetylcholine
C. Epinephrine
D. Norepinephrine

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks which chemical or hormone is released by the parasympathetic nervous system (PNS).

2. **Identifying the Parasympathetic Nervous System**: The PNS is a part of the autonomic nervous system that regulates involuntary bodily functions. It is responsible for the 'rest and digest' functions of the body.

3. **Key Neurotransmitter of PNS**: The primary neurotransmitter released by the PNS is acetylcholine. This neurotransmitter is crucial for transmitting signals in the autonomic nervous system.

4. **Differentiating Other Options**:
- **Serotonin**: Known as the "happy hormone," it is involved in mood regulation but is not primarily associated with the PNS.
- **Epinephrine (Adrenaline)**: Produced by the adrenal glands, it is more associated with the sympathetic nervous system, which prepares the body for 'fight or flight' responses.
- **Norepinephrine (Noradrenaline)**: Similar to epinephrine, it is also produced by the adrenal glands and functions in the sympathetic nervous system.

5. **Conclusion**: Since acetylcholine is the main neurotransmitter released by the parasympathetic nervous system, the correct answer is acetylcholine.

**Final Answer**: Acetylcholine

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