The olfactory receptor neuron has a fast working negative feedback response upon depolarization. When the neuron is depolarizing, the CNG ion channel is open allowing sodium and calcium to rush into the cell. The influx of calcium begins a cascade of events within the cell. Calcium first binds to calmodulin to form CaM. CaM will then bind to the CNG channel and close it, stopping the sodium and calcium influx. CaMKII will be activated by the presence of CaM, which will phosphorylate ACIII and reduce cAMP production. CaMKII will also activate phosphodiesterase, which will then hydrolyze cAMP. The effect of this negative feedback response inhibits the neuron from further activation when another odor molecule is introduced.