From this point on, we enter the realm of hypotheses and conjectures. The basis of the excitation of the olfactory receptor, as with any other nerve cell, is the depolarization of the cell membrane. Let us recap: Every cell contains potassium ions, while the extracellular space contains sodium ions. Thus, there is a significant potential difference between the inside and outside of the cell membrane. If external influences alter the membrane’s permeability to these two types of ions, their concentrations on both sides of the membrane also change. This leads to an immediate change in the electrical potential. The electrical signal thus generated propagates as a nerve impulse along the length of the neuron. Two states are possible for the neuron: polarized (signal “+”) and depolarized (signal “−”). Intermediate states are not possible.