Cranial nerves Flashcards
Cranial nerve 1 name
Olfactory
Cranial nerve 1 anatomical coruse
- Unique: only cranial nerve to attach directly to cerebrum
- Anatomical course
◦ Olfactory epithelial nerve cell bodies leave via cribriform plate of ethmoidal bone
◦ Synapse in the olfactory bulb above cribriform plate from which mitral cells (2nd order) send axons in olfactor tract to the olfactory cortex
Cranial nerve 2 is called? Unique factor
Cranial nerve 2: OPTIC
* Unique: 1 million fibres + envagination of dicephalon
Cranial nerve 2 course
◦ Retinal ganglion cells give axons that lead to vision - exiting eyeball at the optic disc through the optic canal
‣ Meninges extend to this point and myelin from oligodendrocytes
Pupillary light reflex path
Pupillary light reflex
* Afferent: CN2
◦ Retina –> optic nerve –> optic chiasm –> optic tract –> lteral geniculate nucleus
* Communication via the midbrain
* Efferent: CN3
* A light is shone into the eye and the pupillary contrictor response is observed for
Cranial nerve 3 called?
Occulomotor
Cranial nerve 3 has 2 types of motor nerve fibres
Somatic motor
Visceral motor
What somatic motor supply does CN3 provide
◦ From midbrain CN3 nucleus through superior orbital fissure
◦ Motor supply to
‣ Superior rectus
‣ Inferior rectus
‣ Medial rectus
‣ Inferior oblique
‣ Levator palpebri superioris
‣ Proprioception for these
Where does CN3 originate and pass through
Midbrain
Superior orbital fissure
What visceral motor efferents come from CN3 - where do they originate? First syanpse? Provide innervation to? What is interesting about them?
◦ Pre-synpatic in Edinger Westfall nucleus of midbrain, post synaptic from ciliary ganglion (node post entry to eye socket) through superior orbital fissure –> PSNS innervation to sphincter pupillae constriction + ciliary body causing contractiona dn accomodation
◦ They are the most superficial fibres i.e. the first affected by compression
CN3 injury results in what movement
Down and out
Dilated pupil
Ptosis
Cranial nerve 4 has what unique feature
Longest intracranial path
From the posterior brain surface rather than anterior
CN4 path
Longest intracranial path
◦ Originates from dorsal mesencephalon and emerges from posteiror brain surface ◦ Enters dura on free edge of cerebellum tentorium and passes in the lateral wall of the cavernous sinus ◦ Enters orbit through superior orbital fissure to inenrvate superior oblique (uses pulley/trochlear) to move eye down, and in (inferior/medial)
CN4 innervates
◦ Originates from dorsal mesencephalon and emerges from posteiror brain surface
◦ Enters dura on free edge of cerebellum tentorium and passes in the lateral wall of the cavernous sinus
◦ Enters orbit through superior orbital fissure to inenrvate superior oblique (uses pulley/trochlear) to move eye down, and in (inferior/medial)
Cn5 has 3 branches?
Opthalmic
maxillary
mandibular
Opthalmic branch of the CN5 has what function
Somatic sensory
Path of CNV1
◦ Path –> from trigeminal ganglion (lateral to cavernous sinus in a dural recess) –> recurrent meningeal branches and anterior meningeal branches –> through superior orbital fissure
‣ Anterior meningeal –> anterior cranial cavity
‣ Posterior ethmoidal nerve gives off recurrent meningeal branches to produce tentorial nerves (post falx cerebri) as welll as of tentorium cerebelli
‣ Continuing opthalmic nerve does sensation to:
* Cornea
* Skin of forehead
* Scalp
* Eyelids
* Mucosa of nasal cavity
* Paranasal cavities
Path and character of CNV2
◦ Somatic general sensory
◦ Path
‣ Meningeal branch of V2 to last aspect of anteiror cranial fossa as well as nervesto the middle meningeal artery
‣ Then passes through foramen rotundum to supply the sensation to skin of face over maxilla, upper lip, maxillary teeth, mucosa of nose, sinuses and palate
