When the stimulus intensity is increased what changes the number of synaptic vesicles released or the amount of neurotransmitter per vesicle?

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

i do not know and i have a 100 in this class