A small area on the mucous membrane that lines the nose (the olfactory epithelium) contains specialized nerve cells called smell receptors. These receptors have hairlike projections (cilia) that detect odors. Airborne molecules entering the nasal passage stimulate the cilia, triggering a nerve impulse in nearby nerve fibers. The fibers extend upward through the bone that forms the roof of the nasal cavity (cribriform plate) and connect to enlargements of nerve cells (olfactory bulbs). These bulbs form the cranial nerves of smell (olfactory nerves). The impulse travels through the olfactory bulbs, along the olfactory nerves, to the brain. The brain interprets the impulse as a distinct odor. Also, the area of the brain where memories of odors are stored—the smell and taste center in the middle part of the temporal lobe—is stimulated. The memories enable a person to distinguish and identify many different odors experienced over a lifetime