Smell receptors. Coloured transmission electron micrograph (TEM) of a section through smell receptors (cilia) projecting from an olfactory neurone (blue). This nerve cell is responsible for detecting smell. The swollen part of the cell is the olfactory vesicle. Information from the receptors is passed to the olfactory bulb in the brain, where it is processed. There are over a million olfactory receptor cells in a human nose, all located in a small area at the back of the nasal cavity. Magnification: x12,000 when printed 10 centimetres wide.