Which feedback mechanism is exemplified by the process of blood clotting?

• A. Negative Feedback
• B. Homeostasis
• C. Equilibrium
• D. Positive Feedback

Answer: (D)

The process is driven by positive feedback: a small initial change prompts responses that amplify that same change, speeding it up until a final outcome is reached. When a blood vessel is injured, platelets adhere at the site and release signaling molecules like ADP and thromboxane A2. These signals recruit and activate more platelets, which in turn release even more signals. That chain reaction rapidly builds a platelet plug and activates the clotting cascade to seal the wound. This amplification is characteristic of positive feedback, because the response reinforces and accelerates the initial stimulus rather than opposing it. After the clot forms, regulatory mechanisms later limit growth and promote clot dissolution, preventing excessive clotting. Negative feedback would work to restore normal conditions and is not how the clotting cascade operates.