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The Function of Nerve Agents.
Nerve agents may be absorbed into the body by a number of diffrent routes. When inhaled, the chemicals may be absorbed at any point between the mucosa of the mouth and the alveoli of the lungs. Other routes include absorption through the skin (especially through a wound), direct absorption through the eye and via the intestinal tract following ingestion of contaminated foodstuffs.

Effective defense against nerve agents involves protection of the whole body.

Once inside, the nerve agents affect the body in the following way. At nerve muscle junctions and many other synapses throughout the body, there exists an enzyme called Acetyl-cholinesterase. The action of this enzyme is to hydrolyse and thus break up molecules of acetylcholine which are released as a result of nerve signals reaching these synapses. In a normal synapse, when a nerve signal is recieved, millions of these acetylcholine molecules are released into the sinaptic cleft (a microscopic space between the neuron and muscle) and bind to acetylcholine receptors on the muscle. Under normal circumstances these are bound only for a few milliseconds as the acetylcholine molecules are rapidly hydrolysed by the acetyl-cholinesterase enzyme.

In the presence of a nerve agent, however, the enzyme becomes inhibited and is unable to hydrolyse the acetylcholine which then remains bound to the receptor. As more nerve signals are recieved, more molecules are released resulting in excessive amounts of acetylcholine in these clefts.

The effect of the nerve agents is to inhibit the hydrloysis of acetylcholine
resulting in a build up of acetylcholine in the synaptic cleft.

There is an additional effect which stems from this build up of acetylcholine. In normal acetylcholine hydrolysis one of the products, choline, is taken back up by the pre- synaptic nerve and recycled to form more acetylcholine. Since hydrolysis is inhibited in an affected synapse, there can only be limited replenishment of acetylcholine stocks. For this reason the effects of exposure to these substances can be irreversable and even with immediate treatment the recovery period could be months, with hugely increased sensitivity to very mild nerve agents such as insecticides.