LEC50: Cranial Nerves I Flashcards
2 types of bone formation of human skull
1) bottom: cartilagenous endochondral
2) face: membranous
which area of the skull is evolutionarily older?
bottom of skull, the chondrocranial base
which area of skull is malleable? which is not? why?
face/vault is malleable
bottom of skull isn’t malleable b/c cranial foramina there, where nerves exit / vascular supply enters
what is fontanella?
soft spot on top of baby’s skull
newborn’s face/vault very malleable; skull base is not malleable
what is hydrocephalus
abnormal accumulation of CSF in brain; increases intracranial pressure inside skull, progressively enlarges head
most common in infants
what view of skull is this
exocranial view of skull
what view of what structure is this? what does it enable visualization of?
endocranial view of skull base
see important foramina
list cranial nerves, by number and name
I: olfactory
II: optic
III: oculomotor
IV: trochlear
V: trieminal
VI: abducens
VII: facial
VIII: vestibulo-cochlear
IX: glossopharyngeal
X: vagus
XI: spinal accessory
XII: hypoglossal
“general” nerve fibers defn, types
fibers that can be found anywhere in the body
4 types:
GSE, general somatic efferent
GVE, general visceral efferent
GSA, general somatic afferent
GVA, general visceral afferent
meaning of “general” re: spinal nerves
found anywhere in the body
meaning of “somatic/visceral” re: spinal nerves
visceral: gut innervated
somatic: not gut innervated
meaning of “efferent/afferent” re: spinal nerves
efferent: motor
afferent: sensory
“special” nerve fibers of the head/neck (3)
1) SVE, special visceral efferent
2) SVA, special visceral afferent
3) SSA, special somatic afferent
what are SVE fibers? why visceral?
MOTOR fibers relating to muscles derived from the branchial arches
VISCERAL designation THOUGH GO TO SKELETAL MUSCLE! because branchial arches at first were part of aero-digestive system
what are SVA fibers?
fibers relating to taste, smell
what are SSA fibers?
non-gut related special sense fibers
vision, balance, hearing
how many types of fibers can a cranial nerve have?
up to 7 because 4 general and 3 special types of fibers
however, max number found is 5!
3 groupings of cranial nerves
1) special sensory nerves
2) myotomal nerves
3) branchiomeric nerves
*3, 4, 5 system of subdividing cranial nerves*
special sensory nerves are?
*3*
I: olfactory
II: optic
VIII: vestibulo-cochlear
myotomal nerves are? general fxn?
III: oculomotor
IV: trochlear
VI: abducens
XII: hypoglossal
innervate skeletal muscle derived from myotomes
*4*
branchiomeric nerves are? general fxn?
V: trigeminal
VII: facial
IX: glossopharyngeal
X: vagus
XI: spinal accessory
nerves related to branchial arches
*5*
fiber type, CNI: olfactory nerve
SVA
fiber type, CNII: optic nerve
SSA
fiber type, CNVIII: vestibulo-cochlear n
SSA
what is misnomer about CNI: olfactory n / why?
not actually a nerve; it’s a brain tract
was called nerve historically, so misnomer stuck
nerve must either: 1) if motor, go from motor nucleus > muscle or 2) if sensory, have a primary sensory neuron in a ganglia - CNI has neither
structure of CNI: olfactory n?
olfactory tract, bulb, nerve
important structures of this image?
olfactory bulb, nerve, tract
specialized sensory epithelium
communicates w/ mitral tufted cell and nerve
hyperosmia
heightened sense of smell
re: CNI, olfactory nerve
cocaine users have hyperosmia
cacosmia
condition where always perceive foul odors, even if none present
what’s unique about CNII: optic nerve structure?
is an optic tract/brain tract, like olfactory nerve- it’s NOT A NERVE
where does CNII: optic nerve run?
from visual cortex > through optic foramena
where is CNI: olfactory n located?
small fibers in nose septum and undearneath in turbiantes lying on superior nasal concha
pass through cribiform plate of ethmoid bone
what foramena is this? what goes through it?
optic foramena
CNII, optic n
how does 1-eyed blindness present in brain?
atrophy of optic n
is brain sensitive to pain?
no, dura surrounding brain is
astrocytoma?
tumor in brain - swelling in brain tissue
where do you find optic astrocytoma?
near chiasm
function of CNVIII
CNVIII: vestibulocochlear nerve
hearing, balance
where does CNVIII: vestibulo-cochlear nerve exit skull base
internal acoustic meatus
fiber type of nerves i nmyotomal nerve group?
all are GSE EXCEPT CNIII, oculomoter, also GVE parasympathetic fibers
nerves of oculomotor system, function
CNIII, oculomotor; IV, trochlear; VI, abducens
move the eyeball
which cranial nerves are innervating this structure
III, IV, VI
what is this condition? what cranial nerve’s affected?
congenital bilateral external rectus palsy
CNVI: abducens palsy
what is major nerve for tongue innervation?
hypoglossal n
what nerve fiber type do all branchiomeric group nerves have?
SVE, because derived from branchial arches
nerve fiber types for CNV, trigeminal n
SVE, GSA
nerve fiber types for CNVII, facial n
SVE: branchial mm - 2nd arch
GSA: general somatic sensation
GVE: parasympathetic fibers
SVA: taste, anterior 2/3 tongue
nerve fiber types for CNIX, glossopharyngeal n
SVE: branchial mm, 3rd arch
GVA: general visceral sensation
GVE: parasympathetic fibers
GSA: general somatic sensation
SVA: taste, posterior 1/3 of tongue
nerve fiber types for CNX, vagus
SVE: branchial mm, 4th arch
GSA: general somatic sensation
GVE: parasympathetic fibers
GSA: general somatic sensation
SVA: taste, epiglottis
nerve fiber types, CNXI, spinal accessory n
SVE: branchial archs 5-6
GSE: spinal part
what innervates mastication muscles?
SVE of CNV, trigeminal n
CNV, trigeminal n, divisions?
V1: opthalmic
V2: maxillary
V3: mandibular
name nerve, divisions
trigeminal n
green: V1, opthalmic
blue: V2, maxillary
salmon: V3, mandibular
sensory field of CNV, trigeminal n, both re: divisions and overall
cause and presentation of trigeminal neuralgia? possible cause?
compression of 1 division of trigeminal n
unrelenting, intense pain
possible cause- artery compressing nerve/branches
functions of CNVII, facial n?
facial expression muscles- smile, frown, close eyelids
carries taste from anterior 2/3 of tongue
where does CNVII, facial n, pass through?
through temporal bone’s internal auditory canal
through parotid gland > facial muscles
what is this example of?
bell’s palsy aka facial palsy
CNVII, facial n, insulted
nerve fibers of glossopharyngeal n, CNIX?
5! most found in any CN (+ vagus also 5)
SVA: branchial, 3rd arch
GVA
GVE: parasympathetic
GSA
SVA: taste, posterior 1/3 tongue
key nerve for gag reflex?
CNIX, glossopharyngeal nerve
what comes out of jugular foramen?
CNIX- glossopharyngeal, CNX- vagus
what structure carries taste?
epiglottis
nerve fibers/their fxns for CNX, vagus?
SVE- branchial, 4th arch
GVA
GVE
GSA
SVA- taste, epiglottis
where are primary sensory neurons of cranial nerves located?
in ganglia OUTSIDE the CNS - like DRGs of spinal nerves
which cranial nerves do not have ganglia?
CNI, CNII because not real nerves
sensory ganglia of the cranial nerves?
CNV: trigeminal (semilunar) ganglion - LARGEST, MOST IMPORTANT
CNVII: geniculate ganglion
CNVIII: vestibular ganglion; cochlearn (spiral) ganglion
CNIX: superior and inferior glosspoharyngeal ganglia
CNX: superior (jugular) and ifnerior (nodose) ganglia
what is a shockingly sensitive part of the body?
auricle
what provides auricular sensation and to where?
CNV- auriculotemporal branch
CNVII- small area, posterior canal wall
CNIX- medial, inner part of tympanic membrane (tympanic n)
CNX- most of ear canal, pt of outer surface of tympanic membrane (auricular br; arnold’s s n)
Greater auricular n (C2, C3)
Lesser occipital n (C2)
nerve fiber types of parts of CNXI, spinal accessory n
SVE- cranial root
GSE- spinal part
what does spinal part of CNXI innervate?
trapezius m- adduct arm, elevate shoulder
sternocleidomastoid m- tilts, rotates head
what happens to cranial part of CNXI, spinal accessory n?
joins CNX, vagus n
what is spinal accessory nerve’s route?
UNIQUE b/c both enters and exits skull:
arises from C1-C5 ventral horn cells; forms trunk
ascends into skull thru foramen magnum
then exits skull thru jugular foramen, with CNX
runs backwards, descends obliquely behidn digastric and stylohyoid muscles to upper pt of sternocleidomastoid; courses obliquely across neck, to trapezius m
