We don’t fully know or are able toodel the details of neurochemistry, but we know some essential features which we can model, action potentials in spiking neuron models for example.
It’s likely that the details don’t actually matter much. Take traffic jams as an example. There is lots of details going on, driver psychology, the physical mechanics of the car etc. but you only need a handful of very rough parameters to reproduce traffic jams in a computer.
That’s the thing with “emergent” phenomena, they are less complicated than the sum of their parts, which means you can achieve the same dynamics using other parts.