Final answer:
Organophosphorous insecticides affect the nervous system by inhibiting acetylcholinesterase, leading to overstimulation of nerve receptors, and can cause toxicity in humans at high doses or with prolonged exposure.
Step-by-step explanation:
Organophosphorous insecticides, such as carbamates, organophosphates, dichlorvos, malathion, and parathion, impact the nervous system by inhibiting the enzyme acetylcholinesterase (AChE). AChE is crucial for breaking down the neurotransmitter acetylcholine (ACh) in the synaptic cleft, which is critical for nerve impulse transmission. When organophosphates inhibit AChE, acetylcholine accumulates in the synaptic cleft, leading to overstimulation of nicotinic and muscarinic receptors, and results in symptoms like muscle twitching, fatigue, and, at high exposures, paralysis or death.
Those compounds are designed to be more toxic to insects than mammals, but high enough doses or long-term exposure can lead to acute toxicity in humans and animals. Organophosphates do not bioaccumulate and break down faster in the environment than chlorinated hydrocarbons, reducing the likelihood of long-term crop residue problems. Nevertheless, exposure, particularly among agricultural workers, remains a significant health concern.
Different individuals can have large variations in their ability to metabolize these compounds. This variance contributes to differential susceptibility to poisoning by these chemicals. Medical personnel treating poisoning victims can also be at risk of secondary poisoning due to excretions or vapors from patients.