Which of the following hormones has no effect on heart beast

Options

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

Answer

To determine which hormone has no effect on heartbeat, we will analyze each of the options provided:

### Step-by-Step Solution:

1. **Identify the hormones listed in the options**:
- Option A: Oxytocin
- Option B: Thyroxine
- Option C: Adrenaline
- Option D: Noradrenaline

2. **Analyze Option A: Oxytocin**:
- Oxytocin is a peptide hormone secreted from the posterior lobe of the pituitary gland.
- Its primary function is to induce strong uterine contractions during childbirth (parturition).
- **Conclusion**: Oxytocin has no direct effect on heart rate or heartbeat.

3. **Analyze Option B: Thyroxine**:
- Thyroxine is a hormone produced by the thyroid gland.
- It plays a significant role in regulating metabolism and can influence heart rate.
- Low levels of thyroxine can slow down the heartbeat, while high levels can increase it.
- **Conclusion**: Thyroxine does affect heartbeat.

4. **Analyze Option C: Adrenaline**:
- Adrenaline (also known as epinephrine) is secreted from the adrenal medulla.
- It is involved in the body's fight-or-flight response, increasing heart rate and strength of heart contractions.
- **Conclusion**: Adrenaline does affect heartbeat.

5. **Analyze Option D: Noradrenaline**:
- Noradrenaline (norepinephrine) is also secreted from the adrenal medulla.
- Like adrenaline, it plays a role in the fight-or-flight response and increases heart rate and blood pressure.
- **Conclusion**: Noradrenaline does affect heartbeat.

6. **Final Conclusion**:
- After analyzing all options, we find that **Oxytocin (Option A)** is the only hormone that has no effect on heartbeat.

### Answer:
The hormone that has no effect on heartbeat is **Option A: Oxytocin**.