There's a fair bit that is well understood, specifically the chemical processes that drive the signals (and that are present in many other types of cells), and

There's a fair bit that is well understood, specifically the chemical processes that drive the signals (and that are present in many other types of cells), and there are mathematical models that have been tested in-vivo and reasonably replicate some dynamics (for example the Hodgkin-Huxley model). But neurons are indeed complicated, and there are a lot of them...