In the context of physiological feedback loops, is blood clotting an example of positive feedback or negative feedback?

• A. Positive feedback, because platelet activation and clotting factor cascades amplify the clotting response until the break in the vessel is sealed.
• B. Negative feedback, because the response counteracts the initial stimulus and returns the system to its set point by decreasing clot formation as bleeding begins.
• C. Positive feedback, because clotting is controlled mainly by a single hormone that directly reverses bleeding without amplification.
• D. Negative feedback, because blood clotting primarily functions to lower body temperature back toward normal.

Answer: (A)

Verified step by step guidance

1. Understand the difference between positive and negative feedback loops: Negative feedback loops work to reverse a change and bring the system back to its set point, maintaining homeostasis. Positive feedback loops amplify a response, pushing the system further in the direction of the initial stimulus until a specific outcome is achieved.
2. Identify the physiological process involved in blood clotting: When a blood vessel is damaged, platelets are activated and release chemicals that attract more platelets, and clotting factors trigger a cascade that accelerates clot formation.
3. Analyze whether the blood clotting process amplifies or reverses the initial stimulus: Since platelet activation and clotting factor cascades increase the clotting response rather than reduce it, this indicates amplification.
4. Conclude that blood clotting is an example of positive feedback because the process intensifies the response (clot formation) until the vessel break is sealed, stopping further bleeding.
5. Recognize that once the clot seals the break, the positive feedback loop ends, preventing excessive clotting, which is a controlled and temporary amplification rather than a continuous process.