[vntok]

output = if (input > locally_stored_threshold) input * locally_stored_weight else 0

This is not very complex and accurately models neurotransmission. What's missing here is the vastness of connections from a particular neuron towards thousands or more other neurons, but the inherent function is definitely not complex.

* weight being either 1 if you adopt a continous modelization (multiple serial input provide multiple serial output) or a float if you prefer the discrete modelization (sum of input to sum of output)