Also known as CN1, the olfactory nerve is the first of 12 cranial nerves located within the head. It relays sensory data to the brain, and it is responsible for the sense of smell.

The nerve’s olfactory receptors are located within the mucosa of the nasal cavity. Unlike many other nerves, CN1 does not possess two trunks. Rather, its sensory fibers extend through the ethmoid bone’s cribriform plate, a part of the skull located behind the nose. Once airborne chemicals and particles enter the nasal cavity, they interact with these neural receptors.

While part of the nervous system, the CN1 does not join the brainstem. It and the optic nerve are the only cranial nerves for which this is true.

CN1 is the shortest cranial nerve within the human head. It can be susceptible to lesions created by blunt trauma damage, which can result from complications of frontal brain lobe tumors, meningitis, and a few other factors. This will lead to a reduced or absent sense of smell. However, even if CN1 is damaged, nasal pain will still be transmitted via the trigeminal nerve.