Answer:
Nerve agent
Explanation:
A nerve agent is a chemical in which on exposure to humans affects the functioning of the nervous system. These chemicals are known to disrupt the process by which messages are transferred to the organs from the nerve. This disruption occurs by blocking the activity of acetylcholinesterase, which is responsible for the catabolism of a neurotransmitter, acetylcholine.
On exposure to a nerve agent, the muscles of the body become paralyzed and early symptoms is production of excess mucous such as in runny nose, pupil constriction and also difficulty in breathing.
These agents are sometimes used in chemical warfare. Examples include sarin, tabun etc.