Cranial Nerves Flashcards
Cranial Nerve I
Olfactory
Special sensory (smell)
Origin: chemoreceptors of olfactory epithelium
Course: enters through cribiform plate in ethmoid bone, ipsilateral sensation. Does not go through the thalamus (unique)
Termination: olfactory bulb
Cranial Nerve II
Optic
Special sensory (vision)
Origin: optic stalks
Course: exit eyeball at optic disk and travel through optic canal, partially crossover at the optic chiasm
Termination: lateral geniculate nucleus (thalamic)
Cranial Nerve III
Occulomotor Motor Origin: Course: Termination:
Cranial Nerve III
Oculomotor
Motor
Origin: oculomotor nuclei in brainstem (somatic and accessory/Edinger-Westphal)
Course: Supplies 4 of the 6 extraocular muscles (superior rectus, medial rectus, inferior rectus, inferior oblique) and levator palpebrae superioris for the eyelid. Proprioceptive afferents come from these muscles. Visceral motor fibres do parasympathetic innervation for smooth muscle in the pupil and accommodation in the ciliary body.
Cranial Nerve IV
Trochlear
Motor + proprioception
Origin: dorsal mesencephalon on the posterior aspect (unique)
Course: Comes from the posterior brain surface and has the longest intracranial course, enter dura mater at the free edge of the cerebellar tentorium and lateral wall of cavernous sinus. Enters orbit through the superior orbital fissure
Termination: superior oblique extraocular muscle.
Cranial Nerve V
Trigeminal
Motor + main general sensory for the head
Origin: pons-medulla-spinal cord
Course: nuclei in the trigeminal ganglion then splits to 3 roots - opthalmis runs through superior orbital fissure, maxillary through foramen rotundum and mandibular through the foramen ovale.
Termination: skin, dura and mucous membranes in the V1/V2/V3 section
Cranial Nerve VI
Abducens Somatic motor + proprioception Origin: pons Course: Emerges between the pons and medulla and runs intradurally through the cavernous sinus, enters the orbit through the superior orbital fissure. Termination: lateral rectus muscle
Cranial Nerve VII
Facial
General + special sensory (taste from anterior 2/3), somatic and visceral motor
Origin: motor nuclei in pons
Course: Travels with CNVIII through the internal acoustic meatus in the temporal bone → longest interosseous path of the CNs. Motor branches:
- Stapedius: protects middle ear in response to loud noise
- Posterior belly of digastric
- Stylohyoid
- Muscles of facial expression and scalp
Termination: geniculate ganglion
Cranial Nerve VIII
Vestibulocochlear
Special sensory
Origin: Vestibular apparatus and the cochlea of the ear
Course: Separates to the 2 nerves when entering the internal acoustic meatus
Termination: Vestibular and cochlear nuclei of the pons and medulla
Cranial Nerve IX
Glossopharyngeal General + special sensory, minor motor Origin: nuclei in medulla Course: Nucleus ambiguus (shared with CN X) does motor fibres, inferior salivatory nucleus supplies parasympathetic to the otic ganglion/parotid, nucleus of solitary tract (shared with CN X) receives afferent fibres. Termination: nuclei in medulla
Cranial Nerve X
Vagus
Sensory, motor and parasympathetic ++
Origin: group of 8-10 rootlets from medulla
Course: Most extensive distribution of all cranial nerves, divides to cranial, cervical, thoracic and abdominal. Nuclei are in the medulla (solitary tract, dorsal motor nucleus of vagus and nucleus ambiguus)
Termination: chemo- and baroreceptors, mucous membranes and taste receptors + motor input to SM and glands
Cranial Nerve XI
Accessory
Motor to back and neck
Origin: motor nuclei of spinal cord
Course: Enters cranium through the foramen magnum and exits via jugular foramen with IX and X, sensory afferents from the cervical plexus
Cranial Nerve XII
Hypoglossal
Motor to intrinsic/extrinsic tongue muscles
Origin: rootlets from caudal brain stem
Course: Exits via the hypoglossal canal, lingual branches supply all of the intrinsic/extrinsic tongue muscles except for palatoglossus
