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ANAT 214 > Cranial Nerves Pt 2 > Flashcards

Cranial Nerves Pt 2 Flashcards

1
Q

DESCRIBE orbit

A

place/socket = cone shaped cavity
bounded by 7 skull bones = neuro and viscerocranium

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2
Q

what does orbit contain

A

eyeball optic nerve, extraocular muscles, neurovascular structures,
lacrimal gland (superior lateral corner of orbit) & various amounts of adipose tissue (fat filler)

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3
Q

which nerve is in orbit

A

optic nerve
CNII

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4
Q

describe orbital fat

A

adipose tissue
cushions and protects orbit contents
promotes smooth eyeball movements
dampens movements of eyes (not shaking around)

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5
Q

name and describe all 7 bones that bound the orbit

A

frontal = roof of orbit
ethmoid = medial wall w/ maxilla (tiny)
lacrimal (ant to ethmoid) = medial wall w/ maxilla (tiny)
palatine = posterior wall near floor of orbit
maxilla = floor mostly, lateral wall too
zygomatic = floor, also lateral wall
sphenoid = posterior and lateral walls - wraps around back for posterior wall

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6
Q

describe eye

A

globe
organized into 3 concentric layers

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7
Q

name layers of eye - superficial to deep

A

sclera
uvea
retina

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8
Q

describe sclera

A

outer fibrous tunic - whites, tough = made of dense ct, protects/maintains shape (structural role - integrity)
continuous anteriorly with transparent cornea = front clear space, cornea part of sclera

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9
Q

describe uvea

A

middle vascular/muscular tunic
controls amount of light and focus

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10
Q

name the 3 components of uvuea

A

choroid
ciliary body/muscle
iris

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11
Q

describe choroid - part of uvea

A

vascular layer - supply eyeball and interior

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12
Q

describe ciliary body - part of uvea

A

muscle
can change shape of lens - for focus
bulge, pulls lens and adjusts concavity and shape = focus light on retina
Readjust image in front or back of retina

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13
Q

describe iris - part of uvea

A

pigmented muscular ring with 2 muscles
organized at 90 degrees to each other
pupillary sphincter
pupillary dilator

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14
Q

describe iris pupillary sphincter - part of uvea

A

concentric fibers - rings
constricts pupil, closes aperture, reduce diameter
when fibers shorten
Parasympathetic

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15
Q

describe iris pupillary dilator - part of uvea

A

radial fibers
dilates pupil, opens up
sympathetic
organized radially

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16
Q

describe retina

A

innermost photosensitive tunic - detects signal
Specialized photoreceptor cells that synapse with neuron whose axons travel together as optic nerve cn II

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17
Q

name parts of retina

A

optic disk
macula

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18
Q

describe optic disk - part of retina

A

WHERE neurons converge - enter optic nerve
NO photoreceptors here = creates small blind spot

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19
Q

describe macula - part of retina

A

area with highest density of photoreceptors
has a zone of peak visual acuity = fovea the (highest density rods and cones, best at detecting all forms of light, straight at back of pupils in anatomical position)

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20
Q

describe spaces - chambers of eye

A

space between iris and cornea = anterior chamber, contains AQUEOUS humour, maintains intraocular pressure and provides nutrition
space posterior to lens = vitreous chamber, contains VITREOUS humour, gel like, maintains shape of eye, metabolic functions

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21
Q

describe optic nerve - gen

A

relays visual stimuli to brain

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22
Q

describe optic nerve - passage

A

receptor cells in retina relay signals via optic nerves through optic anal
at optic chiasm X = left and right visual field signals sorted into optic tracts and projected to contralateral side of brain for processing (visual-occipital lobe)
bilaterally symmetrical but right has role in left and vice versa

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23
Q

describe optic nerve - exit

A

cn ii passes through optic canal (hidden under lesser wing of sphenoid) = immediately above superior orbital foramen

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24
Q

describe extraocular muscles

A

turn eye towards light
eyeball moved by 6 extraocular muscles = 4 rectus and 2 oblique
controlled by cn III, IV & VI = all pass through sof - mostly dedicated to things around eye (eyeball, eye muscles, skin around eye, skin of forehead)

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25
Q

describe intraocular muscles

A

pupillary dilator and sphincter and cilliary muscles of uvea

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26
Q

name rectus muscles - extraocular eye muscles

A

medial rectus
lateral rectus
superior rectus
inferior rectus

27
Q

describe medial rectus

A

rotates eye medially in transverse plane
ADDUCTS

28
Q

describe lateral rectus

A

rotates laterally = ABDUCTS
away from midline

29
Q

describe superior rectus

A

elevates - rotates superiorly
intorsion = medial rotation in relation to superior

30
Q

describe inferior rectus

A

depresses eyeball
rotates inferiorly
extorsion = lateral rotation in relation to superior side (north or noon)

31
Q

name oblique muscles - extraocular eye muscles

A

superior oblique
inferior oblique
muscles complement superior and inferior rectus muscles

32
Q

describe superior oblique

A

depresses, ABDUCTS and produces intorsion

33
Q

describe inferior oblique

A

elevates, ABDUCTS and produces extorsion

34
Q

what muscles produce pure elevation of eye

A

inferior oblique and superior rectus
(IO compensates for SR)

35
Q

what muscles produce pure depression of eye

A

superior oblique and inferior rectus
SO compensates for adduction and extorsion of IR

36
Q

describe attachment of rectus muscles

A

common tendinous ring around optic nerve to anterior half of eyeball at 4 cardinal points
common tendinous ring attached to sphenoid, around optic canal

37
Q

describe attachment of superior oblique muscle

A

common tendinous ring to posterior/superior half of eyeball via trochlea
Changes course to attach to superior aspect of eyeball –> deep to superior rectus

38
Q

describe attachment of inferior oblique muscle

A

infero-medial orbit wall (maxilla) to post/inf surface of eyeball between inferior and lateral rectus
off maxillary bone and runs laterally to insert itself on inferior of eye (inferior to inferior rectus)

39
Q

describe innervation of
extraocular muscles

A

medial rectus, superior rectus, inferior rectus and inferior oblique = cn III oculomotor
superior oblique = cn VI trochlear
lateral rectus = cn VI abducens
(LR6SO4)3

40
Q

describe cn III

A

oculomotor
levator palpebrae superioris
psns and sns

41
Q

describe cn III psns/sns

A

in bright light = pupil constriction, parasym, craniosacral outflow, sphincter pupillae
in dim light = pupil dilation, symp, t1-t4, dilator pupillae

42
Q

why do superior and inferior rectus muscles produce intorsion and extorsion respectively

A

orbital and visual axes not parallel
so SR and IR both cause adduction and axial rotation (torsion) of eye ball around visual axis
both positioned medially to visual axis
angle = misalignment of visual and orbit axis

43
Q

describe levator palpebrae superioris

A

elevation of upper eyelid, above superior rectus, keeps eyes open
no inferior muscle to keep bottom lid open

44
Q

where are middle and inner ear

A

in petrous portion temporal

45
Q

describe external ear - functions

A

collect and direct- funnels soundwaves towards middle/inner ear- sound waves through auditory canal

46
Q

describe external ear - structures

A

auricle - pinna (visible ear) and its supporting cartilages
includes external auditory meatus and external auditory canal
ends at tympanic membrane (eardrum)

47
Q

describe middle ear - transduction

A

transduces sound pressure waves into mechanical vibrations = reduces energy loss at air to liquid transition (sound waves - mechanical sound pressure into waves/forces that inner ear can interpret)
Involves series of 3 linked ossicle

48
Q

is middle ear open to nasopharynx

A

yes by auditory - eustachian tube
otherwise all energy lost when air wave hits liquid
the 3 ossicles turn sound –> mechanical waves

49
Q

Describe middle ear structures

A

air filled cavity located in petrous portion of temporal
Inferior to middle cranial fossa
external opening sealed by tympanic membrane
contains 3 ear ossicles in sequence

50
Q

describe middle ear - ossicles

A

malleus - handle embedded in tympanic membrane
incus - connects to stapes
stapes - linked to inner ear at (plate sits in) oval window
all responsible for sound transduction

51
Q

describe middle ear - bony openings

A

3 covered = tympanic opening, oval and round window
1 open to nasopharynx via auditory tube = pressure equalization of middle ear and outside (yawn, airplane)

52
Q

describe inner ear - gen

A

sensory component of ear-converts fluid waves to electrical impulses for hearing (cochlea) & balance (vestibular apparatus)
impulses transmitted to brain via CNVIII= Vestibulocochlear nerve via internal acoustic meatus (IAM)

53
Q

describe inner ear - structures

A

consists of bony labyrinth = closed series of bony cavities (tubular spaces) in petrous temporal, filled with fluid (spiral up pyramid)
Divided into cochlea and vestibular apparatus (semicircular canals and vestibule)
encloses separate membranous labyrinth (tube within tube) - matches shape of bony labyrinth

54
Q

describe cochlea

A

in membranous labyrinth, known as cochlear duct (blind ended at apex of cochlea)
Filled with endolymph - liquid outside it (within cochlear canal of bony labyrinth=perilymph)

55
Q

describe cochlea duct separation

A

cochlear canal into 2 channels that meet at apex =
scala vestibuli = spirals up canal towards apex - ascending
scala tympani = spirals down to end at round window, blind end- descending

56
Q

describe sound transduction steps 1-8

A

1- sound waves hit tympanic membrane
2 Makes chain of ossicles vibrate
3 - Stapes plate pushing back and forth into oval window
4 - moves perilymph”up” Scala vestibuli
5 - distance up spiral proportional to frequency of sound (and amplitude)
6 - perilymph in scala vestibuli pushes on cochlear duct (membranous labyrinth, liquids incompressible)= stimulating spiral organ receptors at that level
7- pressure waves on floor of cochlear duct passed on to scala tympani
8- move “down” cochlear canal to be dissipated at Round windows membrane

57
Q

describe spiral organ (of corti)

A

embedded in cochlear duct floor against scala tympani
contains specialized receptor cells that stimulate the fibers of CN VIII (connected to)

58
Q

describe vestibular apparatus

A

Occupies second half of bony labyrinth
bony labyrinth spaces here filled with a membranous labyrinth containing endolymph (location of sensory cells)
membranous labyrinth = semicircular ducts (3) and utricle and saccule

59
Q

describe semicircular ducts - gen

A

located in semicircular canals of bony labyrinth
each at 90 degrees to each other (good at picking up head rotation in space along the 3 coronal planes)
at base - closest to vestibule of bony labyrinth = each duct has thickening = ampulla

60
Q

describe semicircular ducts - detect movement

A

Specialized cells in ampullae detect movement of endolymph and stimulates cnVIII (brain interprets as head rotation)
each semicircular duct is best at detecting fluid motion along one axis in 3D (but works with others to achieve balance)

61
Q

describe utricle and saccule - gen

A

located in vestibule of bony labyrinth between semicircular canals and cochlear canals
continuous with semicircular ducts (utricle) and cochlear duct (saccule)

62
Q

describe utricle and saccule - detect motion

A

detects both linear accelerations as well as head position (like if upside down)
via stimulation of hair cells embedded in gel like thickening of endolymphatic duct walls

63
Q

describe cn VIII

A

vestibulocochlear
relays auditory and balance stimuli to brain from hair cells in vesitbular organ (balance) or cochlea (hearing)
connects to membranous labyrinth and enters skull via IAM in petrous temporal bone onto brain–> between pons and medulla

ANAT 214 (25 decks)

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