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Neuro Final > Vestibular > Flashcards

Vestibular Flashcards

1
Q

what are does vestibular system do (4)

A
  1. balance
  2. coordinates head and eye movements to stabilize images on the retina
  3. muscle tone and posture
  4. unconscious
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2
Q

what are the movements to hold gaze steady

A
  1. vestibular
  2. visual fixation
  3. optokinetic
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3
Q

what are the movements to shift gaze

A
  1. saccades
  2. pursuits
  3. vergence
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4
Q

which CN is used for vestibular and auditory info to be sent to the brainstem

A

CN 8

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5
Q

what is the peripheral organ of our auditory system

A

chochlea

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6
Q

what organ transduces rotational movements

A

semicircular canals

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7
Q

what organ transduces linear acceleration

A

otolithic organs

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8
Q

each labyrinth has a both and membranous component

-the membranous labyrinth is surround by ______ and filled w/ _______

A

perilymph

endolymph

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9
Q

the bony labyrinth is etched in _____

and filled w/ ______

A

bone

perilymph

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10
Q

the membranous labyrinth fits in ______ and filled w/ ______

A

bony labyrinth

endolymph

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11
Q

what are the membranous parts of the….
vestibule
cochlea
semicircular canals

A

utricle and saccule
cochlear duct
semicircular ducts

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12
Q

the bony labyrinth is…..
the membranous labyrinth is….
-what do its walls contain

A

bone
connective tissue and epithelium
-its walls contain the sensory receptors

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13
Q

what are the special sensory receptors that are located in the walls of the membranous labyrinth?
how do we know that these are vestibular hair cells?

A

hair cells

-specifically, vestibular hair cells receptors bc of the presence of the kinocilium

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14
Q

how will your brain know your head just moved

A

hair cells get deflected when your head moves

-mechanical stimulation

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15
Q

what occurs between hair cells to ensure that endolymph and perilymph dont mix

A

tight junctions near the microvillar end of the cells

-forming part of the diffusion barrier btwn endolymph and perilymph

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16
Q

what is deflection of stereocilia towards the kinocilium

what is deflection away

A
  • excitatory (depolarization)

- inhibitory (hyperpolarization)

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17
Q

what are the 2 parts of the vestibular labyrinth

what do they respond to

A
  1. otolith organs -responds to linear acc (translations)
    - utricle
    - saccule
  2. semicircular canals-angular acceleration (rotations)
    - ant (sup)
    - horiz (lateral)
    - posterior
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18
Q

you can experience linear acceleration due to either _____ or _____

A

translational movement
-horizontal plane (side to side, forward-backward)

gravity

  • vertical plane
  • tilting
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19
Q

inside each organ is a small patch of sensory neuroepithelium called the ______

A

macula

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20
Q

the macula contains the ______

A

hair cell receptors

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21
Q

why do the otolith organs respond to linear acceleration?

they are diff than the semicular canals

A

the otoliths have otoconia-calcium carbonate crystals, the canals dont

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22
Q

deflection in the excitatory direction means the firing rate is going to go ……
-inhibitory direction, the firing rate is going to go….

A

up

down

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23
Q

when you tilt your head, gravity will pull ont he otoconical mases which will result in the …

A

mechanical deflection of the hair cell receptors

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24
Q

when udnergoing a trnslational acceleratoin, you go forward but the heavier otoconia ______, thereby deflecting the hair cell receptors

A

lag behind

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25
Q

what kind of motion do the saccule sense

what do the utricle sense

A

up-down

side to side translation and tilt

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26
Q

the utricle’s macula is in the _____ plane and responds best to _____

A

horizontal

linear acceleratoin due to translational movemnet and gravity

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27
Q

where is the saccule’s macular located on

A

medial wall of the vestibule, oriented in the vertical plane

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28
Q

in the saccule, how do the hair cells face

what about in the utricle

A

sacc: hair cells face away from striola
utricle: hair cells face towards striola

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29
Q

how are the hair cells oriented so they allow sensitivity to linear motion in all directions

A

due to the curvature, hair cells are oriented at different angles

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30
Q

how are the hair cells aligned int he semicicular canals vs the macula

A

SCC: hair cells aligned in the same direction (good for direction of rotation)
utricle and saccule macula: hair cells on either side of the striola oreinted opposite to each other

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31
Q

are the canals responsive to gravity?

A

NO1!!! only the otoliths are

32
Q

what are the the membranous labyrinth of the SCC

A

ampulla of the semicircular duct

-(contains the hair cell receptors that is surrounded by perilymph and filled w/ endolymph)

33
Q

what is the patch of sensory neuroepithelium of the ampulla

  • where do the hair cell processes project onto
  • what is the ampulla filled w/
A

crista ampullaris

  • contains the hair cell receptors
  • those hair cells processes project into a gelatinous specialization called the cupula
  • filled w/ endolymph
34
Q

why is the semicircular duct not affected by gravity

A

bc the cupula and endolymph have the same specific gravity

35
Q

what can cause BPPV (benign paroxysmal positional vertigo)

A

the otoconia can get dislodged and migrate into the endolymph of the semicircular duct, causing vertigo and nystagmus (old people)
-makes the canal sensitive to gravity when it normallly only reponds to head rotation

36
Q

how do we get the vestibular sensory info to the brain (and then to the EOMS)
and wehre?

A

CN 8 at the junction of the pons and medulla (pontomedullary junction)

37
Q

how does sensory info from CN8 about head position enter the brainstem

  • where does it travel btwn
  • where wil it eventually synapse
A

at the cerebellopontine angle

  • btwn the inf cerebellar peduncle and the spinal trigeminal tract
  • vestibular nuclei of the rostral medulla and caudal pons located w/in the lateral recess of the floor of the 4th ventricle
38
Q

hair cell receptors of the crista ampullari sand maculae are innervated by the peripheral processes of bipolar neurons located in _____

A

scarpa’s ganglion

39
Q

where is scarpa’s ganglion located in

A

the internal auditory meatus

40
Q

what is the superior division of the central process of the vestibular apparatus innervate ?

what does it travel w/

A

superior canal
lateral canal
utricle

travels with the facial nerve

41
Q

what does the inf division of the central process of the vestibular apparatus innervate?

what does it travel w/

A

the saccule and post canal

-travels w/ the cochlear nerve

42
Q

the peripheral processes of bipolar cells innervate the hair cells int he ______ and ______
-their cell body is where?

A

maculae (saccule and utricle)

-cell body is in scarpa’s ganglion (in IAM)

43
Q

the central processes leaving scarpa’s ganglion form the ________.
-this travels through the internal auditory canal w/ CN7, traverses the subarachnoid space, and enters the lateral brainstem at the _______

A 
vestibular nerve (CN 8) 
-cerebellopontine angle
44
Q

the central processes of cell bodies in vestibular ganglion synapse in ….

A
  1. most go to vestibular nuclei in medulla

2. some go to cerebellum

45
Q

where are vestibular nuclei located at

A

rostral/open medulla (and caudal pons)

-located in the LATERAL RECESS in the floor of the 4th ventricle

46
Q

what are teh 4 parts to vestibular nuclei

A

superior
inf
lateral
medial

47
Q

hwere will CN 8 synapse in

A

lateral brainstem in the lateral recess

48
Q

where does CN8 enter the brainstem at
what is this between
wehre does it synapse at

A 
the CPA (btwn pons and cerebellum), btwn the ICP and spinal trigmeinal nuclues 
-synapse on the vestibular nuclei
49
Q

other CN 8 fibers will bypass the vestibular nuclei completely and instead go through the ____ straight into the cerebelllum

A

ICP

50
Q

what are some of the outputs from the vestibular nuclei

A
  1. spinal cord
  2. thalamus
  3. reticular fomration
  4. cerebellum
  5. EOM nuclei
  6. vestibular nuclei on other side
51
Q

the secondary vestibular fibers project to the ____

  • they are thought ot be involved in what
  • how
A

cord

  • feedback circuits, important for making fast compensatory postural adjustments in response to something that’s thrown you off balance
  • activate limb extensor (antigravity) muscles
52
Q

what does the lateral vestibulospinal tract do

is it crossed or uncrossed

A
  • facilitates the activation of limb extensor (antigravity) muscles when the OTOLITH ORGANS signal deviations from stable balance and upright posture
  • uncrossed
53
Q

the medial vestibulospinal tract does what?
crossed or uncrossed?
what is it a part of?

A
  • regulates head position by reflex activation of neck muscles in response to the stimulation of semicircular canals resulting from rotational accelerations of the head
  • crossed and uncrossed
  • part of the MLF
54
Q

where do the lateral vestibulospinal tract synapse at

A

extensory motor neurons at all cord levels

-keeps your stance and balance

55
Q

where does the medial vestibulospinal tract synapse at

A

on extensor motor nuerons in cervial and thoracic regions for head/neck adjustments

56
Q

after the thalamus, vestibular info heads to the vestibular cortex which is in the….

A

post central gyrus of the parietal lobe

then to VP thalamus then to vestibular nuclei

57
Q

all sensory info must synapse in ____ before being allowed to continue on to cortex

A

thalamus

58
Q

the response of the secondary vestibular fibers can be…

A
  • VOR vestibular ocular reflex (horizontal and vertical)

- or physiologic nystagmus

59
Q

which CN do vertical and torsional eye movements (SR, IR, SO, IO)
which CN do horizontal eyemovements (MR, LR)

A

CN 3 and 4

CN 6 and 3

60
Q

do the pathways for VOR synapse at the thalamus/cortex?

A

no

61
Q

the angular vestibulo-ocular reflex is a dysnaptic neural reflex that connects the ____ to the ______ CN nuclei
-what do these respond to

A

semicircular canals to the eye muscle cranial nerve nuclei of 3, 4, 6
-respond to head rotations (specifically angular acc)

62
Q

what organ is used in the linear VOR

A

otolith organs (utricle and saccule) which respond to head translations (ex. elevator) and tilts

63
Q

the horizontal VOR pathway is what kind of head movmenet

-how do eyes move in respect to this

A

“no, no” head movmeent

  • yaw axis
  • eyes move away from head movment
64
Q

the Horizontal VOR is a 3 neuron arc
where is the first order neuron
where is the 2nd
where is the 3rd

A

1st: cell body in Scarpa’s ganglion (vestibular gang)
2nd: cell body in vestibular nuclei
3rd: CN 6 and CN 3

65
Q

Horizontal VOR

  • what does the peripheral branch of the first neuron innervate
  • where will its central branch (CN8) synapse in
A
  • innervates hair cells in the horizontal canals

- its central branch is going to synapse in the medial vestibular nucleus, which is the rostral medulla/caudal pons

66
Q

where will the 2nd order neurons of the horizontal VOR sned its signal to

A

across to the abducens nerve ont he other side

-takes innervation from the firs torder neuron, CROSSES over, excites the cells in abducens nucleus

67
Q

when your head turns to the left, what does it excite? where does that signal go?

A

excites left horizontal (lateral) canal, that signal comes in, excites the left vestibular nucleus, that sends a signal over to the right abduces nucleus

68
Q

what CN is in the afferent limb of the horizontal vestibulo-ocular reflex?
what is the efferent limb?
what is the interneurnon

A

afferent: CN8
efferent: CN 3, 6
interneuron: MLF

69
Q

what is skew deviation

where does it start and end

A

a vertical misalignment due to a lesion along the graviceptive pathway which starts in the inner ear (utricle) travels up the entire brainstem and ends in the rostral midbrain (INC)

70
Q

what is the organization of the crossed oculomotor nuclei

A

4: SO
3: SR, IR, IO

71
Q

what does the cerebellum do to the translational movements

A

cerebellum keeps most of these movements in check such that counterroll is only about 10% of head roll and the vertical displacements are minimal

72
Q

damage the right ear pathway is equivalent of ____ head tilt

A

left

73
Q

in response to the right tilt (roll) what do the eyes do for vertical alignment?
where is the counter roll?
how does the head get tilted?

A

right eye moves up
left eye moves down

  • counter-roll to “left”
  • gets tilted opposite (to the left)
74
Q

in a normal head tilt to right shoulder, what will the elevated eye do? what will the depressed eye do

A

elevated eye: intort

depressed eye: extort

75
Q

in utricular pathway for lateral head tilting, utricular projections synapse in the _____ which issues fibers that _______ and ascend in the ____ to the subnuclei of the 4 vertically acting EOMs

A

vestibular nucleus
cross
MLF

76
Q

what are the subnuclei of the utricular pathway

A

the fourth nerve nucleus and the 3rd nerve subnuclei controlling the SR, IR, and IO muscles
-4th nerve nucleus and the SR subnucleus innervate their respective muscles of the contralteral eye

77
Q

lesion along the “left ear” graviceptive pathway leads to decreased signal. what happens

A

brain perceives shift and incorrectly assumes head was tilted to right shoulder
-activates the right ear graviceptive pathway to cuase
OD to elevate/intort
OS to depress/extort

Neuro Final (10 decks)

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