In the context of homeostatic control systems, blood clotting is an example of which type of feedback loop?

• A. Negative feedback, because platelets inhibit further platelet aggregation as the clot grows.
• B. Neither positive nor negative feedback, because clotting occurs only by voluntary control.
• C. Negative feedback, because clotting reverses the initial stimulus to keep blood flow constant.
• D. Positive feedback, because each step amplifies the clotting response until a clot forms.

Answer: (D)

Verified step by step guidance

1. Understand the concept of feedback loops in homeostatic control systems: Negative feedback loops work to reverse a change and maintain stability, while positive feedback loops amplify a response until a specific outcome is achieved.
2. Analyze the blood clotting process: When a blood vessel is damaged, platelets adhere to the injury site and release chemicals that attract more platelets, amplifying the clotting response.
3. Recognize that this amplification continues until a clot fully forms to seal the injury, which is characteristic of a positive feedback loop rather than a negative one.
4. Contrast this with negative feedback, which would involve mechanisms that reduce or stop the response to maintain equilibrium, which is not the case in blood clotting.
5. Conclude that blood clotting is an example of a positive feedback loop because the process intensifies itself until the clot is complete.