Cranial Nerve Overview Flashcards
(21 cards)
Name the Cranial Nerves (12 pairs)
CN I Olfactory CN II Optic CN III Oculomotor CN IV Trochlear CN V Trigeminal CN VI Abducent CN VII Facial CN VIII Vestibulocochlear CN IX Glossopharyngeal CN X Vagus CN XI Accessory CN XII Hypoglossal
Describe the pathway of the Olfactory (CN I)
- Fiber type: Special sensory
- Cranial exit: Cribriform foramina
- Pathway: Olfactory bulb Cribriform foramina Olfactory nerves in nasal cavity
- Target: Olfactory nerves in nasal mucosa (smell)
Describe the pathway of the Optic (CN II)
- Fiber type: Special sensory
- Cranial exit: Optic canal
- Pathway: Optic chiasm Optic nerve Optic canal
- Target: retina (sight)
Describe the pathway of the Oculomotor (CN III)
- Fiber type: Somatic motor and parasympathetic
- Cranial exit: Superior orbital fissure
-Pathway:
•Cavernous sinus Superior orbital fissure Muscles located in orbit
•Parasympathetic pathway: Cavernous sinus Superior orbital fissure Ciliary ganglion (synapse)
-Targets:
•Somatic motor targets: levator palpebrae superioris m., extraocular muscles: superior, medial, and inferior rectus, inferior oblique
•Parasympathetic targets: Ciliary muscle and sphincter pupillae muscle
Describe the pathway of the Trochlear (CN IV)
- Fiber type: Somatic motor
- Cranial exit: Superior orbital fissure
- Pathway: Cavernous sinus -> Superior orbital fissure -> Superior orbit
- Target: superior oblique muscle
Describe the pathway of the Trigeminal (CN V)
- Somatic sensory and somatic motor
- There are three divisions of this nerve: Ophthalmic (CN V1), Maxillary (CN V2), Mandibular (CN V3)
Describe the pathway of the Ophthalmic (CN V1)
- Fiber type: Somatic sensory only
- Cranial exit: Superior orbital fissure
-Pathway: Trigeminal ganglion -> Superior orbital fissure -> Through orbit
Major Targets: Skin of forehead, scalp, upper eyelid, cornea, mucosa of anterior nasal cavity and frontal/ethmoidal sinuses
Describe the pathway of the Maxillary (CN V2)
- Fiber type: Somatic sensory only
- Cranial exit: Foramen rotundum
- Pathway: Trigeminal ganglion -> Foramen rotundum -> Branches travel through pterygopalatine fossa to either inferior orbital fissure and orbit or inferior targets
- Major Targets: Skin of face, lower eyelid, upper lip, maxillary teeth and gingivae, scalp, maxillary sinuses, mucosa of posterior nasal cavity and hard & soft palate
Describe the pathway of the Mandibular (CN V3)
- Fiber Type: somatic sensory and somatic motor
- Cranial exit: Foramen ovale
- Pathway: Trigeminal ganglion -> Foramen ovale -> Branches (lingual nerve, etc) and travels inferior, posterior or anterior to targets
- Targets:
1) Somatic sensory targets: portion of scalp near anterior auricle, external tympanic membrane, skin of face, cheek, lower lip, mandibular teeth and gingivae, TMJ, anterior 2/3rds tongue
2) Somatic motor targets: muscles of mastication (temporalis, masseter, lateral & medial pterygoids), mylohyoid, anterior belly of digastric m, tensor veli palatini and tensor tympani mm.
Describe the pathway of the Abducent (CN VI)
-Fiber type: Somatic motor only
-Cranial exit: superior orbital fissure
-Pathway: Cavernous sinus -> superior orbital fissure -> lateral orbit
Target: Lateral rectus muscle
Describe the pathway of the Facial (CN VII)
- Fiber types: Somatic motor, special sensory, parasympathetic, and sympathetic
- Cranial exit: Stylomastoid foramen
- General Pathway: Internal acoustic meatus facial canal gives off three branches (chorda tympani, branch to stapedius muscle, greater petrosal) exits facial canal via stylomastoid foramen travels inferiorly
-Targets: Somatic motor to stapedius, muscles of facial expression (buccinator, occipitofrontalis, orbicularis oris, orbicularis oculi, platysma), stylohoid m., posterior belly of digastric
Describe the pathway of the Chorda tympani: Portion of the Facial (CN VII)
- Middle ear -> Hitchhike on lingual nerve (CN V3) -> anterior & posterior to targets OR -> Submandibular ganglion (synapse) -> oral cavity.
- Special sensory target: anterior 2/3rds of tongue (taste)
- Parasympathetic target: submandibular and sublingual glands
Describe the pathway of the Greater Petrosal: Portion of the Facial (CN VII)
- Exit temporal bone -> joins with deep petrosal nerve (carries sympathetic fibers) -> pterygoid canal -> pterygopalatine ganglion (synapse) -> Hitchhike on CN V2 -> travels anteriorly
- Parasympathetic/sympathetic target: Lacrimal gland and mucosa of nasal cavity
Describe the pathway of the Vestibulocochlear (CN VIII)
- Fiber type: Special sensory only
- Cranial exit: Internal acoustic meatus
- Pathway: Internal acoustic meatus -> Divides into vestibular and cochlear nerves -> inner ear
- Targets:
1) Vestibular n. targets are vestibule and semicircular canals (balance)
2) Cochlear n. target is cochlea (hearing)
Describe the pathway of the Glossopharyngeal (CN IX)
- Fiber types: Somatic sensory, Visceral sensory, Special sensory, Somatic motor, Parasympathetic (visceral motor)
- Cranial exit: Jugular foramen
- Pathway: Jugular foramen -> Gives off tympanic nerve (see below) and then travels inferiorly to most targets
- Major Targets:
1) Somatic motor target: stylopharyngeus muscle
2) Visceral sensory target: carotid body and sinus
3) Somatic sensory target: mucosa of oropharynx, posterior 1/3 of tongue, soft palate
4) Special sensory target: posterior 1/3 of tongue (taste)
Describe the pathway of the Tympanic nerve: Portion of the Glossopharyngeal (CN IX)
- Re-enters skull through temporal bone -> travels through middle ear -> lesser petrosal branch exits middle ear -> foramen ovale -> otic ganglion -> hitchhikes on auriculotemporal branch of CN V3
- Tympanic nerve targets:
1) Somatic sensory target: internal surface of tympanic membrane
2) Parasympathetic target: parotid gland
Describe the pathway of the Vagus (CN X)
- Fiber types: Somatic sensory, special sensory, somatic motor in the head and neck.
- Remember: provides parasympathetic innervation to targets in thorax and abdomen.
- Cranial exit: jugular foramen
- Pathway: Jugular foramen -> Travels inferiorly -> Gives off superior laryngeal branch (see below) near hyoid -> Travels inferiorly -> Branches into recurrent laryngeal nerve (see below) -> Travel around aortic arch and brachiocephalic trunk superiorly to larynx.
- Targets:
1) Somatic motor targets: pharyngeal constrictors, muscles of palate (levator veli palatini, palatoglossus, palatopharyngeus, NOT tensor veli palatini), esophagus
2) Special sensory targets: epiglottis and palate (taste)
Describe the pathway of the Superior laryngeal: Portion of Vagus (CN X)
- Branches into internal branch and external branch
- Targets:
1) Somatic sensory targets (internal branch): laryngeal mucosa superior to vocal folds
2) Somatic motor target (external branch): cricothyroid muscle
Describe the pathway of the Recurrent laryngeal: Portion of Vagus (CN X)
- After traveling around aortic arch and brachiocephalic trunk, changes names in larynx to inferior laryngeal nerve.
- Targets:
1) Somatic motor targets: most intrinsic muscles of larynx (transverse & oblique arytenoid mm., posterior cricoarytenoid, lateral cricoarytenoid, thyroarytenoid)
2) Somatic sensory targets: laryngeal mucosa inferior to vocal folds.
Describe the pathway of the (Spinal) Accessory (CN XI)
- Fiber type: Somatic motor only
- Cranial exit: Jugular foramen
- Pathway: Superior spinal cord -> ENTERS skull through foramen magnum -> EXITS skull via jugular foramen -> Neck muscles
- Targets: Sternocleidomastoid and trapezius muscles
Describe the pathway of the Hypoglossal (CN XII)
- Fiber type: Somatic motor only
- Cranial exit: Hypoglossal canal
- Pathway: Hypoglossal canal -> Travels inferiorly medial to tongue -> Anteriorly toward intrinsic and extrinsic tongue muscles
- Targets: Intrinsic tongue muscles and Extrinsic tongue muscles (hyoglossus, genioglossus, styloglossus).
