Head anatomy with olfactory nerve. Source: Patrick J. Lynch, medical illustrator. Creative Commons Attribution 2.5 License 2006.
The olfactory nerve is the first cranial nerve, which conveys smell sensations (as nerve impulses) from the nose to the brain. Each of the two olfactory nerves detects smells by means of hair-like receptors in the mucous membrane lining the roof of the nasal cavity. Nerve fibers pass from the receptors through tiny holes in the roof of the nasal cavity and come together to form two structures called the olfactory bulbs. From the bulbs, nerve fibers travel to the olfactory center in the brain.