Is blood clotting an example of a positive or negative feedback mechanism? explain your answer based on the description of the mechanism.

ii. blood clotting must happen quickly in order to be useful to the body. explain how this type of feedback mechanism is useful for accelerating the clotting process.

iii. imagine that a toxin in the bloodstream denatures the molecules that signal for platelets. predict how this would affect this feedback mechanism and the person's body as a result.

Blood clothing is an example of positive feedback.

This type of feedback mechanism is useful to the body because it multiplies the factor that intervenes in clotting accelerating the process.

If a toxin affects the molecules that signal for platelets the feedback will not be effective enough to produce clotting and the body will keep bleeding.

Explanation:

Blood clotting is an example of positive feedback due to the fact that when the vascular endothelium is damaged  platelets will go to this area and activate themselves once they are in contact with the collagen fibers of the damaged structure. When the platelets are activated they will release the contents that is stored in their granules. One of the contents is a Gq-linked protein receptor cascade,  that will increase the concentration of calcium in the platelets. Calcium activates protein kinase C, which, in turn, activates phospholipase A2 (PLA2). PLA2  will modifies  an  integrin membrane  increasing its affinity to bind fibrinogen. The activated platelets change their  shape , and the fibrinogen cross-links with the integrin membrane aiding  in  the aggregation of adjacent platelets. After this the coagulation cascade takes place. there are two pathways the extrinsic  and the extrinsic one.

The extrinsic pathway will be activated due to tissular factor released  by the platelets and the intrinsic pathway will be activated due to endothelial collagen. The final product of both pathways is factor x.

Factor x will transform prothrombin into thrombin will activate the conversion of fibrinogen into fibrin. Thrombin will form a net of fibrin that will the clot.

A cascade reaction is useful because every component of the cascade are related making a quick reaction once that one of then is activated and can activate other or more factors.

If a toxin affects the molecules that signals for platelets, platelets will not go to the damaged area and in consequence there will not be thrombin and fibrin to form the clot together with platelets.

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