Cranial Nerves

Question 1

CN I

Answer 1

• olfactory nerve
• The crista galli is a median ridge of bone that projects from the cribriform plate of the ethmoid bone.
• The olfactory bulbs lie on either side of the crista galli on top of the cribriform plate

Question 2

CN II

Answer 2

• optic nerve
• passes through the optic canal

Question 3

name the 4 cranial nerves that carry preganglionic PS fibers out of the CNS

Answer 3

preganglionic cell bodies are found in nuclei inside the CNS

• Edinger Westphal nucleus (CN III)
• superior salivatory nucleus (CN VII)
• inferior salivatory nucleus (CN IX)
• dorsal motor nucleus of the vagus (CN X)

Question 4

describe CN III

Answer 4

• oculomotor nerve
• exits cranial vault and enters orbit through sup. orbital fissure
• motor to elevator of upper eyelid and 4 extraocular muscles
• parasymp. preganglionic fibers -> synapse at ciliary ganglion -> postganglionic fibers to ciliary muscle and pupillary constrictor

Question 5

describe the pupillary light reflex

Answer 5

• CN II = afferent limb
• CN III = efferent limb (parasymp. component)
• Light in R eye -> R pupil constricts (direct light reflex) AND L pupil constricts (consensual reflex)

Question 6

describe the accomodation reflex

Answer 6

• CN II (afferent limb) and CN III which is the PS component (efferent limb)
• attempt to focus on near object -> pupil constricts (pupillary constrictor muscle)
• the lens “fattens up” (ciliary muscles contract) for increased refraction

Question 7

describe function of CN IV

Answer 7

• IV = trochlear nerve
• motor to 1 extraocular muscle; superior oblique

Question 8

CN III, IV, VI

Answer 8

• III = oculomotor nerve
• IV = trochlear nerve
• VI = aducens nerve
• passes through the superior orbital fissure (in sphenoid bone)
  
  • V-1 also passes through SOF

Question 9

describe function of V-1

Answer 9

• opthalmic: exits via superior orbital fissure
• sensory to eye, forehead, part of nasal cavity, paranasal sinuses meninges (dura mata)

Question 10

describe function of CN V2

Answer 10

• maxillary
• 2nd portion of the trigeminal nerve
• passes through the f. rotundum (rotwondum)
• entirely sensory to cheek, upper lip, lower eyelid, and upper teeth, part of paranasal sinuses, tympanic membrane, meninges

Question 11

describe function of CN V3

Answer 11

• mandibular
• 3rd portion of the trigeminal nerve
• passes through the f. ovale (ovalthree)
• sensory: lower lip, lower teeth, chin, ant. 2/3 of tongue, meninges (dura mata)
• motor: mandibular nerve (muscles of 1st pharyngeal arch)

Question 12

describe the sensory innervation of CN V

Answer 12

Question 13

describe function of CN VI

Answer 13

• abducens nerve
• motor to one extraocular muscle, the lateral rectus

Question 14

Answer 14

Question 15

describe CN VII

Answer 15

• exits cranial vault through internal acoustic meatus with CN VIII
• travels through facial canal in temporal bone and exits skull via stylomastoid foramen (main motor branch)

Question 16

describe the motor branch of CN VII

Answer 16

• motor branch exits the temporal bone at the stylomastoid foramen and passes through the parotid salivary gland
• motor to muscles of 2nd pharyngeal arch:
  
  • stapedius
  • auricular muscles
  • stlohyoid
  • digastric (post. belly)
  • muscles of facial expression
• preganglionic PS fibers for all glands in the head EXCEPT parotid gland
• special sense (taste) from ant. 2/3 of tongue
• general sensation from a small part of outer ear

Question 17

name the motor branches of CN VII

Answer 17

Two Zebra Bit My Clavicle

Question 18

what are the 2 branches of CN VII carrying preganglionic PS fibers?

Answer 18

1. greater petrosal nerve -> pterygopalatine ganglion
2. chorda tympani -> submandibular ganglion to submandiular and sublingual salivary glands

Question 19

describe CN VIII

Answer 19

• VIII = vestibulocochlear nerve
  
  • passes through internal acoustic meatus
• involved in special senses:
  
  • hearing (cochlear nerve)
  • aiding balance: head rotation/movement sense (vestibular nerve)

Question 20

CN IX, X, XI

Answer 20

• IX = glossopharyngeal nerve
• X = vagus nerve
• XI = accesssory nerve
• passes through jugular foramen

Question 21

CN XII

Answer 21

• XII = hypoglossal nerve
• passes through hypoglossal canal

Question 22

describe CN IX

Answer 22

• glossopharyngeal nerve
  
  • passes through jugular forament w/ CN X and XI
• general sensation from most of pharynx, posterior 1/3 of tongue, palatine tonsil, middle ear mucosa and tympanic membrane
• PS (preganglionic) fibers for parotid salivary gland
• motor for stylopharyngeus muscle
• visceral afferents from carotid sinus and carotid body