Basically the title says it all. I’ve just always been curious about this since I first noticed it.
In: 3
To put it simply, it works the same way muscles contract and relax. The drug targets a receptor (I.e. a drug molecule binds to another molecule in your body) which illicits a nervous system response which causes it.
It’s actually very complex when considering all the different drugs and mechanisms, but this is the gist.
Opioids and some other sedatives cause the muscles responsible for dilating/constricting the pupil to relax, so the pupils constrict. Psychedelics and stimulants are excitatory and cause the muscles to contract, dilating the pupils.
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