Art-labeling Activity: Positive feedback and blood clotting Cell damage releases chemicals that begin blood clotting The process of positive feedback ends with blood clot formation Cells cell fragments and soluble blood proteins begin clot formation Each step of clotting releases chemicals that accelerate the process A break in a blood vessel wall causes bleeding Chemicals Positive feedback loop Clotting accelerates
The correct answer and explanation is:
Answer: Positive Feedback in Blood Clotting
The correct sequence of events in the positive feedback loop for blood clotting is as follows:
- A break in a blood vessel wall causes bleeding.
This triggers the clotting process to prevent excessive blood loss. - Cell damage releases chemicals that initiate blood clotting.
Damaged cells and platelets release signaling molecules, such as tissue factor, which activate the clotting cascade. - Cells, cell fragments (platelets), and soluble blood proteins begin clot formation.
Platelets aggregate at the site of the injury, forming a temporary “platelet plug,” while soluble blood proteins like fibrinogen are activated to form fibrin threads. - Each step of clotting releases chemicals that accelerate the process.
As platelets stick to the damaged area, they release chemicals such as adenosine diphosphate (ADP), thromboxane A2, and clotting factors. These substances recruit and activate more platelets, amplifying the clotting response. - The process of positive feedback ends with blood clot formation.
The positive feedback loop concludes when a stable clot forms, sealing the vessel break and stopping the bleeding.
Explanation of Positive Feedback in Blood Clotting
Positive feedback mechanisms amplify an initial signal, driving processes to a swift conclusion. In blood clotting (also known as hemostasis), positive feedback ensures rapid and efficient clot formation. When a blood vessel is injured, the exposed collagen and tissue factor activate platelets and the clotting cascade. Platelets adhere to the injury site and release chemicals that recruit more platelets. Simultaneously, the clotting cascade amplifies the production of thrombin, an enzyme that converts fibrinogen into fibrin, creating a mesh that stabilizes the clot.
This cascade is self-reinforcing: each step releases factors that enhance subsequent steps, ensuring rapid clot formation. However, the process is tightly regulated to prevent excessive clotting (thrombosis), as anticoagulants and inhibitors in the blood limit the clot to the injury site. The positive feedback loop is crucial for survival, as it prevents excessive blood loss from injuries.