The part of the neuron whose name literally means "branch" is a(n)

an active site is a region that is present on an enzyme where the reactants or the substrate molecules we can say bind and experience a chemical reaction. the substrate is basically a reactant whose concentration is changing and that is converting into a product after binding at the active site of an enzyme

answer: substrate concentration. enzymes work best when there is a high enough substrate concentration for the reaction they catalyse.