In our brains there are 5-ht receptors that psilocin binds to . 5-ht is serotonin, so normally serotonin binds at 5-ht receptors. Exactly how shrooms work is not fully understood, but I do know psilocin (A metabolite of the psilocybin found in shrooms.) is a postsynaptic ( The receiving end of a synapse.) 5-ht2A receptor ( A type of 5-ht receptor.) agonist, ( A substance that binds to a receptor and triggers a response in the cell ( In this case a neuron.)) which means psilocin binds to the receiving end of a synapse ( The connection between 2 neurons in this case.) at the 5-ht2A receptors, then triggers a response in the neurons which in turn causes widespread neuronal excitation.

My explaination is also oversimplified.