Cranial Nerves
CN 0 - Cranial nerve zero
CN I - Olfactory
CN II - Optic
CN III - Oculomotor
CN IV - Trochlear
CN V - Trigeminal
CN VI - Abducens
CN VII - Facial
CN VIII - Vestibulocochlear
CN IX - Glossopharyngeal
CN X - Vagus
CN XI - Accessory
CN XII - Hypoglossal

The terminal nerve, or cranial nerve zero, was discovered by German scientist Gustav Fritsch in 1878 in the brains of sharks. It was first found in humans in 1913,^[1] although its presence in humans remains controversial. However, a study has indicated that the terminal nerve is a common finding in the adult human brain^[2]. It projects from the nasal cavity, enters the brain just a little bit ahead of the other cranial nerves as a microscopic plexus of unmyelinated peripheral nerve fascicles.

The nerve is often overlooked in autopsies because it is unusually thin for a cranial nerve, and is often torn out upon exposing the brain. Careful dissection is necessary to visualize the nerve. Its purpose and mechanism of function is still open to debate; consequently, nerve zero is often not mentioned in anatomy textbooks.^[1]

Although very close to (and often confused for a branch of) the olfactory nerve, nerve zero is not connected to the olfactory bulb, where smells are analyzed. This fact suggests that the nerve is either vestigial or may be related to the sensing of pheromones. This hypothesis is further supported by the fact that nerve zero projects to the medial and lateral septal nuclei, and the preoptic areas, all of which are involved in regulating sexual behavior in mammals.^[1]

The zebrafish has been used as a model in recent research.^[3]

[edit] References

[edit] See also

• Vomeronasal organ

[edit] External links

• Diagram at kent.edu ("nervus terminalis", #4)

v • d • e Nerves of head and neck: the cranial nerves and nuclei (TA A14.2.01, GA 9.855) olfactory (AON->I) olfactory bulb · olfactory tract optic (LGN->II) optic chiasm · optic tract oculomotor (ON, EWN->III) superior branch (parasympathetic root of ciliary ganglion/ciliary ganglion) · inferior branch trochlear (TN->IV) no significant branches trigeminal (PSN,TSN,MN,TMN->V) trigeminal ganglion • ophthalmic • maxillary • mandibular abducens (AN->VI) no significant branches facial (FMN,SN,SSN->VII) near origin nervus intermedius • geniculate inside facial canal greater petrosal (pterygopalatine ganglion) · nerve to the stapedius · chorda tympani (lingual nerve, submandibular ganglion) at stylomastoid foramen posterior auricular · suprahyoid (digastric, stylohyoid) · parotid plexus (temporal, zygomatic, buccal, mandibular, cervical) vestibulocochlear (VN, CN->VIII) cochlear (striae medullares, lateral lemniscus) • vestibular (Scarpa's ganglion) glossopharyngeal (NA, ISN, SN->IX) before jugular fossa ganglia (superior, inferior) after jugular fossa tympanic (tympanic plexus, lesser petrosal, otic ganglion) • stylopharyngeal branch • pharyngeal branches • tonsillar branches • lingual branches • carotid sinus vagus (NA, DNVN, SN->X) before jugular fossa ganglia (superior, inferior) after jugular fossa meningeal branch · auricular branch neck pharyngeal branch (pharyngeal plexus) · superior laryngeal (external, internal) · recurrent laryngeal (inferior) · superior cervical cardiac thorax inferior cardiac · pulmonary · vagal trunks (anterior, posterior) abdomen celiac · renal · hepatic · anterior gastric · posterior gastric accessory (NA,SAN->XI) cranial · spinal hypoglossal (HN->XII) lingual branches

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