Which of the following is an example of negative feedback ?

Options

A. Sucking reflex
B. Uterine contractions during labor
C. Secretion of CRH in response to ACTH
D. Hair erection due to low body temperature

Answer

To determine which of the options provided is an example of negative feedback, we will analyze the concept of negative feedback and the options given.

### Step-by-Step Solution:

1. **Understanding Negative Feedback**:
- Negative feedback is a regulatory mechanism in biological systems where an increase in one substance leads to a decrease in another, and vice versa. This creates a balance and helps maintain homeostasis.

2. **Analyzing the Options**:
- We will look at the options provided and evaluate each one in the context of negative feedback.

3. **Option A - Sucking Reflex**:
- The sucking reflex in infants is an involuntary action triggered when the roof of the mouth is touched. This reflex helps in feeding but does not involve a feedback mechanism where one process decreases as another increases. Therefore, this is **not** an example of negative feedback.

4. **Option B - Uterine Contractions during Labor**:
- During labor, the secretion of oxytocin increases, which leads to stronger uterine contractions. This is a positive feedback loop where the increase in oxytocin leads to more contractions, not a decrease. Hence, this is also **not** an example of negative feedback.

5. **Option C - Body Temperature Regulation**:
- When body temperature drops, hair erects (pyloerection) to trap heat, which is an adaptation but does not involve a feedback mechanism where one process decreases as another increases. Thus, this is **not** an example of negative feedback.

6. **Option D - CRH and ACTH Secretion**:
- Corticotropin Releasing Hormone (CRH) is secreted by the hypothalamus to stimulate the release of Adrenocorticotropic Hormone (ACTH) from the pituitary gland. When ACTH levels are high, CRH secretion decreases, demonstrating a clear negative feedback mechanism. This is because the presence of ACTH indicates that there is no need for more CRH, thus fulfilling the criteria for negative feedback.

### Conclusion:
The correct answer is **Option D - CRH and ACTH Secretion** as it exemplifies negative feedback.

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