Newton's law still holds, by virtue of the correspondence principle. Which goes something like: The new theory must reduce to the old under the same conditions.
Re: apples
There is no theory of apples. Apples are described. Those neurons are holding a description, not a theory. I'm sure you are just trying to make the point though, that theories and descriptions are representations of reality, not the reality itself.
Theories are laws governing phenomena, or models of reality that are composed of those laws. The models are always mathematical constructions. Being that the theory governs reality, anyone can test it. It must be falsifiable and not contradict other valid theories.
Descriptions are fuzzy. Theories are not and they have mathematical form like F=ma, or E=mc2.
Theories are a way of predicting what we will witness.