Hormone with no effect on beat is

Options

A. Oxytocin
B. Adrenaline
C. Noradrenaline
D. Thyroxine.

Answer

To determine which hormone has no effect on heartbeat, we will analyze each option provided in the question.

### Step 1: Analyze the options
The options given are:
1. Oxytocin
2. Adrenaline
3. Noradrenaline
4. Thyroxine

### Step 2: Understand the function of each hormone
- **Adrenaline**: This hormone is produced by the adrenal medulla and is known as a stress hormone. It plays a significant role in the "fight or flight" response, which includes increasing heart rate. Therefore, adrenaline does affect heartbeat.

- **Noradrenaline**: Similar to adrenaline, noradrenaline is also produced by the adrenal medulla and contributes to the "fight or flight" response. It increases alertness and also raises heart rate. Hence, noradrenaline also affects heartbeat.

- **Thyroxine**: This hormone is produced by the thyroid gland and is involved in regulating metabolism. While it primarily increases the metabolic rate and oxygen uptake in cells, it also has an indirect effect on heart rate by influencing overall metabolism. Thus, thyroxine also affects heartbeat.

- **Oxytocin**: This hormone is secreted by the posterior lobe of the pituitary gland and is primarily involved in childbirth and lactation. It causes contractions of the smooth muscles in the uterus during labor but does not have a direct effect on heart rate or heartbeat.

### Step 3: Conclusion
Based on the analysis, the hormone that has no effect on heartbeat is **Oxytocin**.

### Final Answer:
The hormone with no effect on heartbeat is **Oxytocin**.

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