Which of the following is an example of a positive feedback mechanism?

• A. Thermoregulation by sweating to cool the body
• B. Regulation of blood glucose levels by insulin
• C. Secretion of parathyroid hormone in response to low blood calcium
• D. The release of oxytocin during childbirth to intensify uterine contractions

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the concept of feedback mechanisms. Feedback mechanisms are processes that help maintain homeostasis in the body. They can be categorized into two types: positive feedback and negative feedback. Negative feedback works to counteract changes and restore balance, while positive feedback amplifies a response to achieve a specific outcome.
2. Step 2: Analyze the examples provided in the question. For each example, determine whether it represents positive or negative feedback based on whether the response amplifies or counteracts the initial stimulus.
3. Step 3: Evaluate the first example, 'Thermoregulation by sweating to cool the body.' Sweating is a negative feedback mechanism because it works to counteract the increase in body temperature by cooling the body down.
4. Step 4: Evaluate the second example, 'Regulation of blood glucose levels by insulin.' Insulin lowers blood glucose levels when they are high, counteracting the change, which is characteristic of negative feedback.
5. Step 5: Evaluate the final example, 'The release of oxytocin during childbirth to intensify uterine contractions.' This is a positive feedback mechanism because the release of oxytocin amplifies the uterine contractions, which further stimulates the release of more oxytocin, creating a loop that intensifies the response until childbirth is complete.