The secretion of vagus nerve , which reduces the heart rate, is

Options

A. dopamine
B. adrenaline
C. epinephrine
D. acetylcholine

Answer

To answer the question regarding the secretion of the vagus nerve that reduces the heart rate, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Role of the Vagus Nerve**: The vagus nerve is a crucial part of the autonomic nervous system and is primarily responsible for the parasympathetic control of the heart.

2. **Identifying the Function of the Autonomic Nervous System**: The autonomic nervous system regulates involuntary bodily functions, including heart rate. It has two main branches: the sympathetic and parasympathetic nervous systems.

3. **Sympathetic vs. Parasympathetic Effects**: The sympathetic nervous system increases heart rate during stress or emergency situations (fight or flight response) by releasing hormones like epinephrine (adrenaline). In contrast, the parasympathetic nervous system, through the vagus nerve, works to decrease heart rate.

4. **Secretion of the Vagus Nerve**: The primary neurotransmitter released by the vagus nerve that reduces heart rate is acetylcholine. When acetylcholine is released, it binds to receptors in the heart, leading to a decrease in heart rate.

5. **Conclusion**: Therefore, the secretion of the vagus nerve that reduces heart rate is acetylcholine.

### Final Answer:
The secretion of the vagus nerve, which reduces the heart rate, is **acetylcholine**.

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