Cranial Nerves Flashcards
CN1
Olfactory
CN2
Optic
CN3
Occulomotor
CN4
Trochlear
CN5
Trigeminal
CN6
Abducens
CN7
Facial
CN8
Vestibulocochlear
CN9
Glossopharyngeal
CN10
Vagus
CN11
Accessory
CN12
Hypoglossal
CN1: Origin & path
Origin: R & L olfactory bulbs
Path: exits skull via cribiform plate
Termination: roof of the nose
CN2: Origin & path
Origin: optic disc
Path: leaves orbit entering skull via optic canal. Runs posterior-medically towards optic chiasm. Decussation of fibres from temporal visual fields of both eyes. Terminates in lateral geniculate nucleus (in thalamus) where information is relayed to visual cortex
CN3: Origin & path
Origin: third nerve nucleus at level of superior colliculus in the midbrain
Path: emerges from ant aspect of midbrain, passing inf to posterior cerebral artery and sup to superior cerebellar artery. Pierced dura mater and enters lateral aspect of cavernous sinus. Leaves cavity via superior orbital fissure. Divides into superior and inferior branches
CN4: Origin & path
Origin: trochlear nucleus
Path: emerges from posterior aspect of midbrain. Runs anterior and inferior within subarachnoid space. Pierces dura mater adjacent to posterior clinoid process. Runs along lateral wall of cavernous sinus. Enters orbit via superior orbital fissure.
CN5: Origin
Origin: 3 sensory nuclei (mesencephalic, principle sensory, spinal nuclei of trigeminal), 1 motor nucleus (motor nuclei of trigeminal).
CN5: path
Path: at level of pons, sensory nuclei merge to form sensory root. In the middle cranial fossa the sensory root expands into the trigeminal ganglion, lateral to cavernous sinus. Gives rise to 3 divisions: ophthalmic (V1), maxillary (V2), mandibular (V3).
CN5: Path of branches
V1: travels lateral to cavernous sinus exiting cranium via superior orbital fissure
V2: travels lateral to CS exiting via foramen rotundum
V3: exits via foramen ovale
CN6: Origin & path
Origin: abducens nucleus located in pons
Path: pierces dura mater through Dorello’s Canal. Sharp then at tip of petrous part of temporal bone to enter CS. Enters orbit through superior orbital fissure
CN7: Origin
Origin: facial nucleus in the pons (sensory & parasympathetic parts from intermediate nerve)
CN7: Path (intercranial)
Two roots: motor and sensory roots
Travel through internal acoustic meatus (of temporal bone). Enters the facial canal. Exits via stylomastoid foramen.
CN7: Inside facial canal
- Motor and sensory roots fuse to become facial nerve
- Nerve forms geniculate ganglion
- Gives rise to: greater petrosal nerve, nerve to stapedius, chorda tympani
CN7: Path (extracranial)
After exiting via stylomastoid foramen, nerve runs superior, just anterior to outer ear. 1st branch: post auricular nerve. 2nd: nerve to digastric. 3rd: nerve to stylohyoid. Main trunk continues ant and inf into the parotid gland. Within the gland it terminates splitting into 5 branches.
CN7: branches
Intercranial: greater petrosal nerve, nerve to stapedius, chorda tympani
Extracranial: posterior auricular nerve, nerve to digastric, nerve to stylohyoid
Terminal: temporal, zygomatic, buccal, marginal mandibular, cervical
CN8: Origins
Origins: vestibular: vestibular nuclei complex in pons and medulla. Cochlear: ventral and dorsal cochlear nuclei in inferior cerebellar peduncle
CN8: path
Vestibular and cochlear fibres combine in the pons to form vestibulocochlear nerve. Emerges from brain at cerebellopontine angle. Exits cranium at internal acoustic meatus (of temporal bone). Within IAM nerve splits to form vestibular and cochlear nerves.
CN9: Origins & path
Origin: medulla oblongata
Path: emerges at anterior aspect of medulla moving laterally in posterior cranial fossa. Leaves cranium via jugular foramen forming superior and inferior ganglia. 1st branch: Tympanic nerve. Descends down neck anterolaterally to internal carotid artery giving of branches.
CN9: Branches
Tympanic nerve
Nerve to stylopharyneus
Pharyngeal branch
Tonsillar branch
Lingual nerve
Carotid sinus branch
CN9: Parasympathetic branches
Origin: inferior salivatory nucleus
Path: Fibres travel with tympanic nerve to ear. Fibres continue as the lesser petrosal nerve before synapsing at Otic ganglion. Fibres hitchhike on the auriculotemporal nerve (V3, CN5) to parotid gland.
CN10: Origin
Origin: medulla of brainstem
CN10: path
Path: gives of auricular branches. Exits cranium via jugular foramen. Passes in the carotid sheath.
R: passes ant to subclavian artery and post to sternoclavicular joint entering thorax. Forms posterior vagal trunk. Enter abdomen via oesophageal hiatus (T10). Terminates by dividing into branches.
L passes inf between L common carotid and L subclavian artery, post to sternoclavicular joint entering thorax. Forms anterior vagal trunk. Enter abdomen via oesophageal hiatus (T10). Terminates by dividing into branches.
CN10: branches
Cranium: auricular branch
Neck: pharyngeal branches, superior laryngeal nerve, (right only) recurrent laryngeal nerve.
Thorax: (left only) recurrent laryngeal nerve, cardiac branches
Abdomen: branches that supply oesophagus, stomach, small and large bowel (up to splenic flexure).
CN11: Origins
Origins: spinal component: C1-C5/6 spinal nerve roots. Cranial: lateral aspect of medulla oblongata.
CN11: Path
Spinal component: fibres (C1-C5/6) coalesce to form spinal part of accessory. Runs superior to enter cranium via foramen magnum. Transverses posterior cranial fossa to reach jugular foramen. Briefly meets cranial portion before exiting skull. Descends along internal carotid to reach sternocleidmastoid. Then moves across posterior triangle of neck to supply trapezius.
Cranial: leave cranium via jugular foramen where it briefly contacts spinal part. Combines with CNX at inferior ganglion on vagus.
CN12: Origins & path
Origin: hypoglossus nucleus of medulla oblongata
Path: passes laterally across posterior cranial fossa. Exits via hypoglossal canal. Passes inferior to angle of mandible crossing internal and external carotids and moving anterior to enter tongue.
CN1: Functions
Smell
CN2: Functions
Vision
CN3: Functions
Motor:
Superior branch:
Superior rectus (elevates eyeball)
Levator palpabrae superioris (raises upper eyelid)
Inferior branch:
Inferior rectus (depressed eyeball)
Medial rectus (adducts eyeball)
Inferior oblique (elevates, abducts, laterally rotates eyeball)
Parasympathetic:
Inferior branch:
Sphincter papillae (constricts pupil)
Ciliary muscles (contracts makes lens more spherical)
CN4: Functions
Motor:
Superior oblique (abduction, depression, internal rotation of eyeball)
CN5: Functions
V1:
Sensory: forehead & scalp, frontal & ethmoidal sinus, upper eyelid, cornea, dorsum of nose.
V2:
Sensory: lower eyelid, cheeks, maxillary sinus, nasal cavity & lateral nose, upper lip, upper molar, incisor & canine, superior palate
V3:
Sensory: mucous membranes & floor of oral cavity, external ear, lower lip, chin, ant 2/3rd tongue (not taste), lower molar/incisor/canine teeth
Motor: muscles of mastication (medial pterygoid, lateral pterygoid, masseter, temporalis), anterior belly of digastric, mylohyoid, tensor veli palatini, tensor tympani
CN5: Branches
V1: Ophthalmic
- frontal
- lacrimal
- nasociliary
V2: Maxillary
- 14 terminal branches
V3: Mandibular
- buccal
- inferior alveolar
- auriculotemporal
- lingual
CN6: Functions
Motor:
Lateral rectus (abduct eyeball)
CN7: Functions
Motor: muscles of facial expression, posterior belly of digastric, stylohyoid and stapedius.
Sensory: small area around the concha of external ear
Special sensory: taste to anterior 2/3 of tongue via chorda tympani
Parasymp: submandibular and sublingual salivary glands, nasal/palatine/pharyngeal mucous glands, lacrimal glands
CN8: Functions
Special sensory:
Hearing
Equilibrium
CN9: Functions
Sensory: oropharynx, carotid body and sinus, post 1/3 tongue, middle ear, Eustachian tube
Special sensory: taste post 2/3 tongue
Parasympathetic: parotid
Motor: stylopharyngeus
CN10: Functions
Sensory: external acoustic meatus, internal surfaces of latyngopharynx and larynx. Visceral sensation to heart and abdominal organs
Special sensory: taste to epiglottis and root of tongue
Motor: muscles of pharynx, soft palate and larynx
Parasympathetic: smooth muscle of trachea, bronchi, GI tract, regulates heart rhythm
CN11: Functions
Motor: sternocleidomastoid, trapezius
CN12: Functions
Motor: muscles of tongue (except palatoglossus)
