head: cranial nerves Flashcards
where do these cranial nerves originate? CNI , CN II, CN XI
I- cerebrum
II- diencephalon
XI- spinal cord
olfactory nerve: where are the receptors, cell bodies, central processes and synapse ?
Receptors in roof of nasal cavity
Cell bodies in nasal mucosa
Central processes enter cranium via cribriform plate
Synapse in olfactory bulb
only CN to enter cerebrum
CN I- olfactory
Olfactory tracts project to where?
Olfactory tracts project to ipsilateral & contralateral anterior temporal lobes
CN II: Optic “nerves” are ___ order neurons
Extensions of ________
3rd, extensions of diencephalon
optic chiasm
Medial (nasal) retinal fibers cross & join lateral (temporal) retinal fibers of contralateral eye
Form optic tracts
optic tracts
R carries fibers from R half of each retina=left visual field
L carries fibers from L half of each retina=right visual field
where do the optic tracts project?
to thalamus then to occipital lobes
oculomotor: CN III - what does it do?
Somatic motor-eye/eyelid movement
Visceral motor-constricts pupil, rounds lens (accommodation)
Efferent limb of light reflex
CN III originates from two midbrain nuclei
- Motor-somatic
- Accessory/parasympathetic (Edinger-Westphal)-visceral
To ciliary ganglion
oculomotor nerve + CN IV + CN VI course
Courses lateral to diaphragm sella, crosses internal carotid
Enters orbit via superior orbital fissure
Short ciliary nerves (V1) go where?
to sphincter pupillae & ciliary body
what is the largest true cranial nerve?
CN V (trigeminal)
trigeminal nerve: made of how many brainstem nuclei? - how many are sensory and how many motor? which are larger? where does it emerge from?
4 brainstem nuclei-3 sensory, 1 motor
sensory (large) & motor (small) roots
pons
*Sensory root has central processes from trigeminal (semilunar) ganglion
trigeminal ganglion is ____ to cavernous sinuses
lateral
do all trigeminal nerve fibers go through the trigem ganglion?
NO! sensory do, but Motor root fibers bypass ganglion
–> Blend with V3 in foramen ovale
three branches of opthalmic V1 and their subdivisions
Lacrimal
Frontal: Supraorbital/supra trochlear
Nasociliary: Long/short ciliary, Infratrochlear
afferent limb of sneeze reflex
maxillary V2
while V2 has 5 branches, which 2 do we care about? what are their subdivisions?
Zygomatic: Zygomaticofacial, Zygomaticotemporal
Infraorbital: Anterior superior alveolar
what are the 4 ganglia in the head? what nerve carries ALL postgang PSNS?
Ciliary Pterygopalatine Otic Submandibular - Postganglionic parasympathetic from all ganglia carried by CN V branches
where does CN VI (abducens) enter to orbit?
comes from posterior cranial fossa
Enters at clivus
- enters orbit via SOF
which nerve has the longest intradural course?
CN VI
which CN has the longest interosseus course?
CN VII
where does the facial nerve enter and exit
enter: IAM (facial canal)
exit: stylomastoid foramen
where does the facial nerve take a sharp bend?
at the geniculate ganglion
three interosseus branches of CN VII (facial)
Greater petrosal
Nerve to stapedius
Chorda tympani
Chorda tympani (of facial nerve) enters infratemporal fossa via ______ _______ to meet with lingual V3
petrotympanic fissure
what innervates the stapedius (muscle that stabilizes the stapes)?
Branch to stapedius from facial nerve CN VII
Facial nerve CN VII- exits cranium via what? to become what 5 extracranial branches?
stylomastoid foramen
temporal, zygomatic, buccal, marginal mandibular, cervical
what do the external branches of facial nerve innervate?
Muscles of facial expression
posterior digastric + stylohyoid
Efferent limb of corneal reflex
Orbicularis oculi
mandibular V3 supplies what muscles?
Mylohyoid
Anterior digastric via Nerve to mylohyoid
Tensor veli palatini
Tensor tympani
where do the two branches of vestibulocochlear nerve go? (CN VIII) - where are the cell bodies of each?
Vestibular to maculae of utricle & saccule, cristae ampullaris of semicircular canals
Cell bodies in vestibular ganglion
Cochlear to spiral organ of Corti
Cell bodies in spiral ganglion
which nerves come from preolivary sulcus of medulla oblongata as rootlets?
CN IX, X and XII
what are the branches of CN IX glossopharyngeal
tympanic, pharyngeal (+ stylopharyngeus), lingual, carotid sinus
what reflexes are the vagus nerve involved in?
Afferent & efferent limbs of cough reflex
Efferent limb of gag reflex
Efferent limb of carotid sinus reflex
what are the C1-C2 fibers that the hypoglossal nerve CN XII carries (but then they depart)
Superior root of ansa cervicalis (C1 ± C2)
Nerves to geniohyoid & thyrohyoid (C1)
which CNs arrive midline? which more lateral?
1-3, 6, 12 emerge near midline
4,5 7-10 emerge more lateral
for each cranial fossa, how many foramina in each? what are they?
Anterior cranial fossa: 1 foramen - cribiform
I
Middle cranial fossa: 4 foramina - optic canal, SOF, rotundum, ovale
II, III, IV, V (1-3), VI
Posterior cranial fossa: 3 foramina - IAM, jugular foramen, hypoglossal canal
VII, VIII, IX, X, XI, XII
CN test I + II
CN I-check for air movement through each nostril; patient occludes one nostril; use distinctive odor 10 cm from each nostril
CN II-hand-held or wall Snellen chart for acuity; Ishihara for color; visual fields by confrontation
CN test III, IV, VI
CN III (autonomic motor)-direct & consensual pupil constriction to light & accommodation
II-afferent, III-efferent
CN III (somatic motor), IV, & VI-ptosis & extraocular movements; follow “H” pattern
LR6 SO4 All Others3
CN test V
CN V (somatic sensory)-cotton swab to V1, V2, V3 distributions, cotton wisp to cornea (blink) V-afferent, VII-efferent CN V (somatic motor)-open/close mouth, palpate temporalis & masseter with clenched teeth
CN test VII
CN VII (somatic motor)-facial symmetry; look up (forehead wrinkles), close eyelids tight, smile, puff cheeks CN VII (special sensory)-rarely tested; salt to anterior 2/3 tongue CN VII (autonomic motor)-rarely tested; dry eyes & mouth
CN test VIII
CN VIII (cochlear)-rub fingers next to ears
Weber-Rinne for conductive vs. sensorineural
CN VIII (vestibular)-rarely tested
Barany test for vertigo, Romberg test for equilibrium
CN test IX/X
CN IX/X (somatic sensory/motor)-say “Ahhh”, soft palate rises with midline uvula; gag reflex; phonation
Uvula deviates AWAY from affected side
IX-afferent, X-efferent
CN IX/X (other functions)-rarely tested; dry mouth
CN test XI and XII
CN XI-turn head, shrug shoulders against resistance
CN XII-stick out tongue
Tongue deviates TOWARDS affected side
what is the “convoluted course of visceral motor to otic ganglion? (4)
- glossopharyngeal Tympanic branch enters middle ear - tympanic plexus near mastoid process
(Visceral sensory & preganglionic parasympathetics) - tympanic n (CN IX) –> Lesser petrosal n. (of CN VII) into middle cranial fossa
- enters infratemporal fossa via foramen ovale
w/ V3 –> otic ganglion - Postganglionics in auriculotemporal (V3) to parotid gland
after the tympanic branch, what are the 3 other branches of the glossopharyngela CN IX?
Pharyngeal branch
Lingual Branch
Carotid sinus branch
what do the pharyngeal, lingual and carotid sinus branches of CN IX do?
- Pharyngeal branch: Forms pharyngeal plexus with X on middle pharyngeal constrictor
Sensory to pharynx; Motor to stylopharyngeus - Lingual branch: General sensation & taste to posterior 1/3 of tongue
- Carotid sinus branch: Afferent baroreceptive & chemoreceptive + Carotid massage
