Cranial Nerves Flashcards
cranial nerves
- Bundles of sensory, motor, or mixed fibers that innervate muscles or glands
- They emerge through foramina or fissures in the cranium
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motor CN
CN III – oculomotor
CN IV – trochlear
CN VI – abducent
CN XI – accessory
CN XII – hypoglossal
sensory CN
CN I – olfactory
CN II – optic
CN VIII – vestibulocochlear
mixed CN
CN V – trigeminal
CN VII – facial
CN X – vagus
CN XI – glossopharyngeal
CN I
- Olfactory
- Type: special sensory
- Course: olfactory receptors on olfactory mucosa -> CN I arise through the foramina of the cribriform plate -> synapse on olfactory bulb -> axons of secondary nerve cells (mitral cells) become olfactory tract
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CN II
- Optic
- Type: special sensory
- Course: axons of 3rd order nerve cells in the retina (retinal ganglion cells) project back to the brain forming the optic nerve (CN II) ->enters cranium through the optic canal -> form the optic chiasm -> posterior to the chiasm becomes the optic tract
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CN III
- Oculomotor
- Type: somatic motor and visceral motor (parasympathetic fibers)
- Course: runs anteriorly in the lateral wall of the cavernous sinus -> enters the orbit through the superior orbital fissure -> branches out into superior and inferior divisions
- Innervation
- Superior division
- Levator palpebrae superioris
- Superior rectus
- Inferior division
- Medial rectus
- Inferior rectus
- Inferior oblique
- Parasympathetic fibers (via short ciliary nerves of ciliary ganglion)
- sphincter pupillae m. (constriction of pupil)
- ciliary m. (accomodation of lens; for distance or close vision)
- Superior division
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CN IV
- Trochlear
- Type: somatic motor
- Smallest cranial nerve, with longest intracranial course
- Course: runs anteriorly in the lateral wall of the cavernous sinus -> enters the orbit through the superior orbital fissure
- Innervation
- Superior oblique m. (uses a pulley or trochlea to redirect its line of action, giving name to CN IV)
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CN VI
- Abducent
- Type: somatic motor
- Course: runs through the cavernous sinus parallel and inferior to internal carotid artery -> enters the orbit through the superior orbital fissure
- Innervation
- Lateral rectus m (abducts the eye)
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CN V
- trigeminal
- Type: somatic sensory and somatic motor
- Principal somatic sensory nerve of the head (face, teeth, mouth, nasal cavity, and dura mater of cranial cavity). Motor root is distributed exclusively via the mandibular division (CN V3)
- Branches or divisions
- Ophthalmic (CN V1)
- Maxillary (CN V2)
- Mandibular (CN V3)
- Opthalmic & maxillary ONLY SENSORY
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CN V1
- Ophthalmic
- Type: sensory only
- Course: runs anteriorly in the lateral wall of the cavernous sinus -> enters the orbit through the superior orbital fissure
- Branches
- Lacrimal n.
- Frontal n.
- Nasociliary n.
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Lacrimal n.
- runs anteriorly along lateral aspect of orbit
- Supply: upper eyelid (sensory)
- Supply: lacrimal gland (parasympathetic fiber from the pterygopalatine ganglion via the zygomatic n. of CN V2)
Frontal n.
- runs anteriorly in the center of orbit
- Supraorbital n. (exits through supraorbital foramen)
- Supratrochlear n. (medial to supraorbital n.)
- Supply: forehead, anterior scalp, and upper eyelid
Nasociliary n.
- runs anteriorly along medial wall of orbit
- Sensory root of ciliary ganglion: sensory fibers from the eyeball pass through
- the ciliary ganglion and join the nasociliary n.
- Long ciliary nerve: supply iris and cornea. Contains sympathetic fibers to
- the dilator pupillae m.
- Infratrochlear nerve: supplies skin of eyelid, side of nose, conjunctiva,
- and lacrimal sac
- Anterior & Posterior ethmoidal nerves: supply ethmoid and sphenoid
- air sinuses and part of nasal cavity
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CN V2
- Maxillary
- Type: sensory only
- Course: goes through lateral wall of the cavernous sinus -> exits cranium via foramen rotundum -> travel in the pterygopalatine fossa
- Major nerves and their branches:
- Zygomatic n
- Infraorbital n
- Nasal branches
- Pterygopalatine ganglion branches
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Zygomatic nerve
- Zygomaticofacial nerve: skin of upper cheek
- Zygomaticotemporal nerve: skin over side of forehead. Carries communicating branch to lacrimal nerve
Infraorbital nerve
- (exits through infraorbital foramen)
- Supply: upper teeth, lower eyelid, upper lip, and part of nasal vestibule
- Posterior superior alveolar nerve: molar teeth and associated gum area
- Anterior & Middle superior alveolar: premolar, canine, and incisive teeth and associated gum
Nasal branches
- Posterior superior and inferior lateral nasal nerves
- Nasopalatine nerve
- Supply walls and septum of nasal cavity
Pterygopalatine ganglion branches
- Ganglion located inferior to the maxillary nerve in the pterygopalatine fossa
- Receives parasympathetic fibers via the greater petrosal nerve from the Facial nerve (CN VII)
- Greater & Lesser palatine nerve: enter nasal cavity and supply palate mucosa and glands
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CN V3
- Mandibular
- Type: sensory and motor
- Course: exits cranium via foramen ovale
- Branches:
- Motor
- Sensory
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Motor branch of Mandibular CN V3
- Muscles of mastication (temporalis, masseter, & lateral and medial pterygoid)
- Tensor veli palatini: in palate, tenses soft palate(when swallowing opens and covers nasal cavity)
- Tensor tympani: in tympanic cavity, dampens sounds (reduce damage to ear)
- Mylohyoid and anterior belly of digastric via mylohyoid nerve
Sensory branch of Mandibular CN V3
- Auriculotemporal nerve: auricle, TMJ, and anterior temporal region
- Parotid branches: parasympathetic fibers from the glossopharyngeal nerve (CN IX) via the lesser petrosal nerve -> otic ganglion->auriculotemporal n.
- Buccal nerve: skin over buccinator m. (cheeks) and internal mucosa membrane of the same area
- Lingual nerve: sensation to anterior 2/3rd of tongue
- Submandibular ganglion branches: visceral fibers from the facial nerve (CN VII) via chorda tympani nerve join the lingual nerve posteriorly to reach the submandibular ganglion
- Supply submandibular and sublingual glands and carry taste fibers from anterior 2/3rd of tongue
- Inferior alveolar nerve: enters mandibular foramen -> runs anteriorly in the body of mandible -> emerges through the mental foramen as the mental nerve
- Supply: mandibular teeth (IAN); skin of chin, and skin and mucosa of lower lip (MN)
*Parasympathetic ganglia and CNs
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3 parasympathetic ganglia associated with the trigeminal nerve
- Pterygopalatine ganglion (from CN VII -> CN V2)
- Submandibular ganglion (CN VII -> lingual nerve of CN V3)
- Otic ganglion (CN IX -> auriculotemporal n. of CN V3)
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cavernous sinus and associated structures
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CN VIII
- Facial
- Type: somatic and visceral motor and sensory
- Course: enters cranium through internal acoustic meatus runs in facial canal (geniculate nucleus) exits cranium through stylomastoid foramen
- Clinical: lesions lead to facial paralysis
- Branches:
- Sensory:
- Geniculate ganglion (also carries taste)
- Motor:
- Stapedius n.
- Post. auricular n.
- Temporal branches
- Zygomatic branch
- Buccal branch
- Mandibular branch
- Cervical branch
- Sensory:
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Geniculate ganglion
- sensory
- Greater petrosal nerve: from geniculate ganglion -> to pterygopalatine ganglion (CN V2 in the pterygopalatine fossa) -> via the zygomatic nerve to lacrimal nerve (CN V1) to lacrimal gland
- Chorda tympani through petrotympanic fissure to submandibular ganglion via the lingual nerve (CN V3) -> to sublingual and submandibular glands. It also carries taste (special sensory) fibers from anterior 2/3rd of tongue
Stapedius nerve
to stapedius muscle in middle ear. Before coming out of stylomastoid foramen
Posterior auricular n.
- runs posterior to auricle
- Muscles of auricle and occipitalis m.
- Posterior belly of digastric, stylohyoid m.
5 motor branches of CN VII that innervate the mm of facial expression after getting into the parotid gland
- temporal branches
- zygmatic branch
- buchal branch
- mandibular branch
- cervical branch
Temporal branches
Course: superior to parotid gland -> crosses zygomatic arch -> to temporal and frontal regions of scalp
Zygomatic branch
Course: anterior to parotid gland -> innervates muscles as it goes forward on the upper cheek
Buccal branch
Course: medially through cheek
Innervate: buccinator. This is motor, remember that CN V3 has a buccal branch as well, but it is sensory
Mandibular branch
Course: along lower border of mandible, innervates muscles on its course
Cervical branch
Course: courses inferiorly to innervate the platysma
*CN VII Facial
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CN VIII
- Vestibulocochlear
- Type: special sensory (hearing and equilibrium and motion)
- Course: Enters the internal auditory meatus with the facial nerve divides in two parts:
- Divisions:
- Cochlear
- Vestibular
cochlear division of CN VIII
Cochlear: to the cochlear or organ of hearing
vestibular division of CN VIII
Vestibular: to the semicircular canal for balance and equilibrium
*CN VIII vestibulocochlear
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CN IX
- Glossopharyngeal
- Type: somatic, visceral, and special sensory (taste) & somatic and visceral motor
- Course: exits cranium through anterior aspect of the jugular foramen. At this foramen the CN IX has two ganglia
- Branches
- Somatic motor
- Stylopharyngeous m.
- Somatic sensory
- Tympanic nerve
- Carotid sinus nerve
- Pharyngeal and tonsillar nerves
- Lingual nerve
- Visceral motor
- Lesser petrosal nerve to otic ganglion
- Somatic motor
Stylopharyngeous m.
somatic motor branch of CN IX
Tympanic nerve
- somatic sensory branch of CN IX
- sensory to middle ear (affected during ear infection)
Carotid sinus nerve
- somatic sensory branch of CN IX
- sensory to carotid sinus (barorec.) and body (chemorec.)
Pharyngeal and tonsillar nerves
- somatic sensory branch of CN IX
- sensory to pharynx, palatine tonsils, and soft palate
Lingual nerve
- somatic sensory branch of CN IX
- sensory and taste (special sensory) to posterior 1/3rd of tongue
Lesser petrosal nerve to otic ganglion
- visceral motor branch of CN IX
- (associated with CN V3) -> auriculotemporal nerve -> to parotid gland
*CN IX Glossopharyngeal
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CN X
- vagus
- Type: somatic, special, and visceral sensory & somatic and visceral motor
- Course: exits cranium through middle aspect of jugular foramen between CN IX and XI and travels inferiorly in the neck in the carotid sheath
- Branches:
- meningeal branch
- auricular branch
- pharyngeal branch
- sup. laryngeal n.
- cardiac branches
- recurrent laryngeal n.
Meningeal branch
- sensory branch of CN X
- sensory to dura mater of posterior cranial fossa, rest of dura mater (CN V)
Auricular branch
- branch of CN X
- tympanic membrane, part of ear canal, and auricle
Pharyngeal branch
- motor and sensory branch of CN X
- motor to pharyngeal mm., except stylopharyngeous (CN IX) & to soft palate, except tensor veli palatini (CN V3). Sensory to lower pharynx, rest of pharynx (CN IX)
Superior laryngeal nerve
- branch of CN X
- Internal laryngeal n.: sensory to larynx (above vocal folds), and soft palate. Taste to root of tongue and epiglottis
- External laryngeal n.: motor to cricothyroid m.
Cardiac branches
- branch of CN X
- visceral motor and sensory to heart and lungs
Recurrent laryngeal nerve
- branch of CN X
- Course: goes inferiorly, wraps around subclavian artery (R) & around aortic arch (L) ascends in the neck in the groove between the trachea and esophagus
- Motor to laryngeal mm., except for cricothyroid. Clinical relevance: damage to this nerve could lead to lack of voice production
- Sensory to larynx (below focal folds)
*CN X vagus
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CN XI
- Accessory
- Type: somatic motor only
- Course: ascends along upper cervical cord -> enters skull through FM -> loops around and exit cranial cavity through posterior part of jugular foramen
- Innervates: SCM & trapezius mm.
*CN XI accessory
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CN XII
- Hypoglossal
- Type: somatic motor
- Course: Exits cranium through hypoglossal canal -> goes anteriorly between ECA and IJV -> runs deep to posterior belly of digastric and stylohyoid mm. to enter the submandibular triangle
- Superior root of Ansa cervicalis runs with hypoglossal n. and provides motor innervation to thyrohyoid and geniohyoid mm.
- Innervate: intrinsic and extrinsic tongue muscles
*CN XII Hypoglossal
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innervation of the tongue
- CN V3 (anterior 2/3rd of tongue sensation)
- CN VII (anterior 2/3rd via chorda tympani and lingual taste)
- CN IX (posterior 1/3rd sensation and taste)
- CN X (taste to root of tongue and epiglottis)
- CN XII (motor to extrinsic and intrinsic m.)
- Clinical relevance: these functions can be used clinically to test the integrity of these nerves
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