Blood coagulation has both positive and negative feedback involved. When bleeding occurs in the human body, it leads to the activation of tissue factor and coagulation factor XII, which activate the exogenous coagulation pathway and the endogenous coagulation pathway, respectively, thus forming the prothrombin complex, which in turn activates the plasminogen, and ultimately causes the fibrinogen to form fibrin monomers. Numerous fibrin monomers aggregate together to form a fibrin network, which in turn, with the involvement of platelets, forms a thrombus for hemostasis. This process is a positive feedback process. When hemostasis is completed, the body regulates the coagulation process through negative feedback to weaken or stop, so as to avoid excessive thrombosis leading to thrombotic diseases, such as cerebral infarction, intravascular thrombosis, and so on. This process relies on the regulation of negative feedback.