Description and Physiology:
This purely sensory cranial nerve conveys nerve impulses from the nasal passage to the brain. We interpret these nerve impulses as smells. The olfactory nerve, outlined in yellow below, is the mechanism through which one is able to experience olfaction, or the sense of smell.
The afferent axons, pictured here as the yellow hair like extensions that line the roof of the nasal cavity respond to volatile small molecule odorants, non-volatile proteins, and non-volatile hydrocarbons. All of the aforementioned cause olfaction sensations, which we perceive as smell.
(FIGURE 1.1) Source: Patrick J. Lynch, medical illustrator. Creative Commons Attribution 2.5 License 2006
Pathophysiology:
- Anosmia – inability to smell
- Cacosmia – things smell like feces
- Dysosmia – things smell different than they should
- Hyperosmia – an abnormally acute sense of smell.
- Hyposmia – decreased ability to smell
- Olfactory Reference Syndrome – psychological disorder which causes the patient to imagine he or she has strong body odor
- Parosmia – things smell worse than they should
- Phantosmia – “hallucinated smell,” often unpleasant in nature
Literature Cited
Olfactory and optic nerve. 2011. Youtube; [updated 2011 Mar 12, cited 2012 May 6]. Available from: http://www.youtube.com/watch?v=DwRAG7BdFAY
12 Cranial Nerves 