A Medical Dictionary definition...
Procoagulant: Relating to or denoting substances that promote the conversion in the blood of the inactive protein prothrombin to the clotting enzyme thrombin.
The term “procoagulants” applied to snake venom toxins seems inappropriate when their effect is actually to remove the body’s ability to clot blood and their dangerous effect is internal (or external) haemorrhage (uncontrolled bleeding). So how does one reconcile the apparent contradiction?
Blood clotting involves a number of concurrent chemical factors and changes which combine to ultimately change prothrombin into thrombin, which then converts fibrinogen, a single protein molecule in the blood, into fibrin strands, made by joining together fibrinogen molecules. These strands form a physical mesh to which platelets (bits of cells designed to assist with clotting) attach, forming a clot that itself adheres to a rupture in the wall of a blood vessel (limited by size of course).
Procoagulant snake venom directly converts prothrombin into thrombin. This may or may not result in a myriad of tiny blood clots throughout the entire body. As a result of the conversion of all the fibrinogen to fibrin, this triggers release of enzymes to break down the fibrin. So the blood ends up stripped of fibrinogen and its ability to clot. In the absence of any further procoagulant toxin, it takes the liver some 12 hours or more to produce and replace the amount of fibrinogen required by the body.
Hope that clears up that point.
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A couple of other technical points that obviously need clarifying...
Hemotoxin is a general term for any toxins which affect the blood or blood vessels.
Procoagulant is a more specific term for a hemotoxin that affects the bloods clotting ability by causing formation and destruction of fibrin by converting prothrombin to thrombin.
Nerve cells connect with other nerve cells or with muscle cells. Theses connections are not direct but consist of a minute physical gap between the two called a synapse. Nerve impulses are transmitted across this gap by the movement of chemicals called neurotransmitters. There are many different neurotransmitters in the body and they have different effects, depending. However, the neurotransmitter that connects all nerves to voluntary/skeletal muscles is acetylcholine. It is this neurotransmitter that is affected by elapid venom neurotoxins. The resultant danger from this toxin alone is respiratory failure due to paralysis of the thoracic muscles (diaphragm and inter-costals).
Acetylcholine also has a minor but non-critical role in the central nervous system.
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