Please answer all questions

1			If a person has been nerve gassed (i.e. exposed to one of the anticholinesterases), one symptom of the condition may be pin-point pupils. Please explain.
2			Angry people can often be seen to have very dilated pupils. Why?
3			The tobacco plant produces nicotine, several giant toadstools produce muscarine, and certain nerve gases (originally produced to kill people) are used as insecticides: what do all of these facts tell us about an insect's neurons?