DESCRIPTION and 
FUNCTION: These tiny nerves run from the nasal mucosa (Figure 1B) to synapse with the olfactory bulbs, which are considered brain structures, not part of the cranial nerve.
The function is purely sensory. The olfactory nerve carries afferent impulses for the sense of smell (click to see a video "How Smell Works").
ORIGIN and COURSE: Olfactory nerve fibers arise from olfactory receptor cells located on olfactory epithelium. They pass through the ethmoid bone to synapse in the olfactory bulb. Fibers of the olfactory bulb neurons extend posteriorly as the olfactory tract, which runs beneath or inferior to the fronal lobe to enter the cerebral hemispheres (Figure 1A). The fibers terminate in the primary olfactory cortex.
CLINICAL TESTING: Person is asked to sniff aromatic substances and to identify each
HOMEOSTATIC IMBALANCE: Fracture of the ethmoid bone or lesions of olfactory fibers may result in partial or total loss of smell, a condition known as anosmia (an-oz'-me-ah).