This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Physiology
[{'content': 'Thrombin activity is inhibited by \nSelect and explain. \nA. Chymotrypsin, B. Heparin, C. Alpha 2 antitrypsin, D. Alpha 2 macroglobulin', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Heparin is present in the luminal surface of vascular endothelium it acts as an anticoagulation by the following mechanism: Prevent conversion of prothrombin to thrombin Inhibit the action of thrombin Facilitate the action of antithrombin III Ref: Medical Physiology Indu Khurana 2015 edition, Page No:159 It is also used as intravenous anticoagulant. Dose-0.5 to 1mg/kg of bodyweight. Action lasts for 1.5 to 4 hrs Injected heparin is destroyed by an enzyme in blood called heparinase', 'role': 'assistant'}]