Smell pathway. Artwork of the pathway involved in the sensation of smelling a flower. The perception of smell starts in the lining (mucosa) of the nose (1), where tiny hair-like receptor nerve cells (2) detect airborne chemicals. Activated receptor cells transmit messages (3) to the olfactory bulb (4), just above the nasal cavity. The olfactory bulb is a swelling on the end of the olfactory nerve which carries the sensory impulses to the brain's smell centres (5). These olfactory centres lie brain's frontal lobes (centre left) and limbic system (6), which interpret the impulses to produce the sensation of smell.