Kranienerver

Gray686.png Fig. 686 - Øvre del av ryggmargen og hind- and midthjerne; posteriørt aspekt, eksponert in situ. (illustrerer flere, men ikke alle kranienervene).]] Kranienerver (Latinsk: Nervi craniales) er nerver som utløper fra hjernestammen.

Navn på nerver

I den humane anatomi forefinnes 12 par kranienerver, som tradisjonelt forkortes med deres korresponderende romerske tall. De er nummerert etter plasseringen av deres cellekjerner (nuclei) i hjernestammen. , f.eks. kranienerve I (nervus olfactorius) forlater hjernestammen fra en høyere posisjon enn kranienerve XII, hvis opprinnelse er mer kaudal enn de andre kranienervene.

Alle kranienerver bortsett fra nervus olfactorius og nervus opticus tilhører det perifere nervesystem, og innehar således axoner som er myelinisert av Schwann-celler (myeliniserende celler i det perifere nervesystem) i stedet for oligodendrocytter (myeliniserende celler i sentralnervesystemet). Nervus olfactorius og nervus opticus benevnes som nerver, men er teknisk sett ikke nerver, men forlengelsen av sentralnervesystemet.

Note: teknisk er nervus accessorius splittet i en spinal accessory nerve og cranial accessory nerve, men den sistnevnte fusjonerer tidlig med nervus vagus.

|- | I || Nervus olfactorius || Anterior olfactory nucleus |- | II || Nervus opticus || Lateral geniculate nucleus |- | III || Nervus oculomotorius || Oculomotor nucleus, Edinger-Westphal nucleus |- | IV || Nervus trochlearis || Trochlear nucleus |- | V || Nervus trigeminus || Principal sensory trigeminal nucleus, Spinal trigeminal nucleus, Mesencephalic trigeminal nucleus, Trigeminal motor nucleus |- | VI || Nervus abducens || Abducens nucleus |- | VII || Nervus facialis (VII) || Facial nucleus, nucleus solitarius, Superior salivary nucleus |- | VIII || Nervus vestibulocochlearis || Vestibular nuclei, Cochlear nuclei |- | IX || Nervus glossopharyngeus || Nucleus ambiguus, Inferior salivary nucleus, nucleus solitarius |- | X || Nervus vagus || Nucleus ambiguus, Dorsal motor vagal nucleus, nucleus solitarius |- | XI || Nervus accessorius (eller cranial accessory nerve or spinal accessory nerve) || Nucleus ambiguus, Spinal accessory nucleus |- | XII || Nervus hypoglossus || Hypoglossal nucleus

#	Navn	Cellekjerner

Kranienerver hos ikke-humane virveldyr

Humane kranienerver er evolusjonsmessig homologt til de som gjenfinnes hos mange andre virveldyr. De første ti kranienerve-par har sitt felles opphav hos tetrapoder (amfibier, reptiler inklusive fugler og pattedyr). Kranienervene XI og XII ble utviklet hos den felles ancestor til amnioter (non-amfibiske tetrapoder), slik at det totalt er tolv par. Disse karakteristika er synapomorfier for deres respektive klader. Hos noen primitive bruskfisker, som f.eks. dogfish (Squalos acanthos), there is a terminal nerve numbered 0 (as it exits the brain before the first cranial nerve).

Huskeregler

As the list is important to keep in mind during the examination of the nervous system, there are many mnemonic devices in circulation to help remember the names and order of the cranial nerves.

Oliver the optimistic octopus trots triumphantly about facing audiances glossily vaguely spinning hippos.
- (Note that the accessory nerve is referred to by its alternate name Spinal accessory nerve, and the Vestibulocochlear nerve by its former name, Auditory, in this mnemonic.)

On Old Olympus' Towering Top A Fin And German Viewed Some Hops
- (Note that the accessory nerve is referred to by its alternate name Spinal accessory nerve, and the Vestibulocochlear nerve by its former name, Auditory, in this mnemonic.)
Ooh, Ooh, Ooh To Touch And Feel Virgin Girls Vaginas, Ahh Heaven!
Ooh, Ooh, Ooh To Touch And Feel Virgin Girls Vaginas And Hymens!
Ooh, Ooh, Ooh To Touch And Feel Very Good Velvet. Such Heaven!
- (Note that the accessory nerve is referred to by its alternate name Spinal accessory nerve in this mnemonic.)
Oh Once One Takes The Anatomy Final Very Good Vacations Are Heavenly
Another to help remember the types of information these nerves carry (sensory, motor, or both) is thus: Some Say Marry Money, But My Brother Says Big Brains Matter More.

See mnemonic for more mnemonic devices to aid remembering the cranial nerves.

Tretten kranienerver?

Although twelve nerves are classically described in humans, there is a theory that finds favour with some authors, that humans really have thirteen cranial nerves (Andy Lelli , 1999). If the C1 spinal nerve were considered the thirteenth cranial nerve, C2 through C8 would be renamed as the first through seventh cervical nerves (though anatomists might change the term 'cervical' to 'nuchal' or some other term to avoid confusion between the two nomenclatures). This would make the numbering system consistent all the way through the spinal column - every nerve would exit below its corresponding vertebra, and the number of vertebrae would equal the number of spinal nerves.

Alternatively, C1 could be considered the spinal root of the hypoglossal nerve (CN XII). This would, again, make the numbering system consistent.

Se også

Cranial nerve nucleus

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