During hemostasis, thrombin plays a central amplifying role. Which action of thrombin is responsible for AMPLIFYING the coagulation cascade rather than just converting fibrinogen to fibrin?

• A Thrombin activates Factor XIII, which cross-links fibrin polymers
• B Thrombin binds thrombomodulin, activating protein C to terminate coagulation
• C Thrombin cleaves von Willebrand factor multimers to enhance platelet adhesion
• D Thrombin activates Factors V, VIII, and XI via positive feedback, exponentially amplifying its own generation ✓

Explanation

Thrombin is the central amplifier of coagulation: it cleaves fibrinogen → fibrin (terminal step) but also feeds back to activate Factors V (cofactor for Xa), VIII (cofactor for IXa in tenase complex), and XI (amplifying intrinsic pathway), creating an explosive burst of thrombin generation. It also activates platelets via PAR-1/PAR-4 receptors. The small initial amounts of thrombin generated in the initiation phase trigger this positive-feedback amplification loop, generating the full thrombin burst needed for stable fibrin clot formation. Factor XIIIa cross-links fibrin; thrombomodulin-bound thrombin activates protein C (anticoagulant pathway — the opposite effect).

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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