Cranial nerves

Question 1

CN I

Answer 1

• olfactory nerve
• -sensory nerve
• -one of two nerves that DONT arise from brainstem
• -cell bodies of nerve located in olfactory mucosa of nose (superior nasal concha & superior part of nasl septum)
• -axons of cells pass through the cribriform plate on way to brain

Question 2

CN II

Answer 2

• optic nerve–sensory nerve
• -nerve of sight
• -fibers of nerve arise from retina (not brain)
• -from each eyeball nerve passes posteriorly to apex of the orbit to exit via optic foramen
• -right and left optic nerves meet at optic chiasma
• optic tracks leave chiasma to terminate in the brain

Question 3

CN III

Answer 3

• oculomotor nerve–motor nerve
• -origin–>ventral surface of brain stem–>pierces dura to enter the cavernous sinus
• -from sinus it enters orbit through the superior orbital fissure
• -provides motor fibers to all the extraocular muscles, EXCEPT 2.
• -carries preganglionic paraS figers to ciliary ganglion (intrinsic eyeball muscle) and proprioception fibers to eyeball muscles
• -damage to nerve results in drooping of upper eye lid (ptosis)

Question 4

CN IV

Answer 4

• trochlear nerve–motor
• -longest intercranial course–>originates from the dorsum of brain stem and penetrates the dura to enter cavernous sinus–>passes through the superior orbital fissure to enter orbit
• -supplies only one muscle–> superior oblique muscle of orbit
• -damage to nerve–>double vision when pt looks downward and outward

Question 5

CN V

Answer 5

• trigeminal verve–mixed (motor & general sensory)
• -nerve of first arch, largest cranial nerve, sensory innervation to head, motor innervation of muscles of mastication and few other muscles
• -emerges from pons by sensory and motor root
• -SEMILUNAR GANGLION–>contains cell bodies of the sensory root fibers–>ganglion forms a shallow groove on the anteromedial side of petrous part of temporal bone, known as TRIGEMINAL IMPRESSION

Question 6

3 divisions of CN V

Answer 6

• ophthalmic-sensory
• maxillary-sensory
• mandibular-mixed

Question 7

Ophthalmic division of CN V

Answer 7

• smallest of 3 divisions
• passes through the cavernous sinus
• divides into branches that enter orbit through the superior orbital fissure & supply the orbit & part of the face with sensory innervation

Question 8

Maxillary division of CN V

Answer 8

• enters the cavernous sinus while still in skull
• exits skull through the foreman rotundum
• 4 major branches–>zygomatic, palatine, nasal, infraorbital
• -zygomatic–>supplies skin over zygomatic bone and skin between and including, the lower eyelid and upper lip
• -palatine–>greater and lesser palatine–>supply the soft and hard palates
• -nasal–>shpenopalatine, nasopalatine–>supply the mucosa of the nose
• -infraorbital–>exits through the infraorbital foramen to supply skin between the lower eyelid and upper lip

Question 9

4 branches of maxillary division

Answer 9

• -zygomatic–>supplies skin over zygomatic bone and skin between and including, the lower eyelid and upper lip
• -palatine–>greater and lesser palatine–>supply the soft and hard palates
• -nasal–>shpenopalatine, nasopalatine–>supply the mucosa of the nose
• -infraorbital–>exits through the infraorbital foramen to supply skin between the lower eyelid and upper lip

Question 10

Mandibular division of CN V

Answer 10

• sensory and motor
• exits skill through the foramen ovale to enter the infratemporal fossa (includes motor root of CN V)
• otic ganglion attached to its trunk
• 5 branches–
• ->motor branches, buccual (long buccal), auriculotemporal, lingual, inferior alveolar

Question 11

5 branches & functions of mandibular division

Answer 11

• MOTOR BRANCHES–>to muscles of mastication
• BUCCAL (LONG BUCCAL)–>sensory to buccal mucosa and adjacent gingiva
• AURICULOTEMPORAL–>encircles the middle meningeal artery—passes through the parotid gland to ascend into the scalp anterior to the ear–sensory to TMJ, external acoustic meatus, skin of temple and scalp–contains postganglionic parasympathetic fibers for the parotid gland
• LINGUAL–>sensory to the anterior 2/3 of the tongue–enters floor of mouth–also carries taste fibers from anterior 2/3 of tongue and parasympathetic fibers to oral glands
• INFERIOR ALVEOLAR–>enter the mandibular foramen and courses through the mandibular canel–motor fibers leave before the nerve enters the mandibular foramen as the mylohyoid nerve–the canal gives sensory branches to the mandibular teeth–its mental branch emerges from the mental forman as the mental nerve

Question 12

Motor branches (Mandibular division)

Answer 12

-to muscles of mastication

Question 13

Buccal (long buccal)-mandibular division

Answer 13

-sensory to buccal mucosa and adjacent gingiva

Question 14

Auriculotemporal (mandibular division)

Answer 14

-encircles the middle meningeal artery—passes through the parotid gland to ascend into the scalp anterior to the ear–sensory to TMJ, external acoustic meatus, skin of temple and scalp–contains postganglionic parasympathetic fibers for the parotid gland

Question 15

Lingual (mandibular division)

Answer 15

-sensory to the anterior 2/3 of the tongue–enters floor of mouth–also carries taste fibers from anterior 2/3 of tongue and parasympathetic fibers to oral glands

Question 16

-inferior alveolar (mandibular division)

Answer 16

-enter the mandibular foramen and courses through the mandibular canel–motor fibers leave before the nerve enters the mandibular foramen as the mylohyoid nerve–the canal gives sensory branches to the mandibular teeth–its mental branch emerges from the mental forman as the mental nerve

Question 17

CN VI

Answer 17

• abducens nerve–motor
• -leaves the brain and traverses the cavernous sinus before passing through the superior orbital fissure to enter the orbit.
• -In the orbit it supplies only one extrocular muscle – Lateral rectus muscle.
• -damage to this nerve the pupils of the eye cannot move laterally beyond the midpoint.

Question 18

CN VII

Answer 18

Facial nerve–motor and sensory (mixed)
Nerve of the 2nd arch
Accompanies CN VIII into the internal auditory (acoustic) meatus.
At distal end of the meatus CN VII enters the facial canal and exits at the stylomastoid foramen.
Facial canal is in the petrous part of the temporal bone.
Distal to the stylomastoid foramen CN VII enters the parotid gland where it divides into its five terminal branches.
Branches given off while in the canal
A. Branch to the stapedius muscle
B. Chorda tympani - contains Preganglionic parasympathetic and taste fibers
C. Greater petrosal nerve - contains preganglionic parasympathetic fibers to the pterygopalatine ganglion. The postganglionic fibers go supply the lacrimal gland.
Branches given off after exiting the stylomastoid foramen
A. Branches to posterior belly of digastric and stylohyoid muscles
B. Branches to muscles of facial expression: temporal, zygomatic, buccal, mandibular and cervical
Type of fibers in CN VII
A. Motor fibers
B. Secretory parasympathetic to sublingual, submandibular and lacrimal glands
C. Taste fibers (special sensation) from anterior 2/3 of tongue and from the palate