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Neuro > The vestibular system > Flashcards

The vestibular system Flashcards

1
Q

what are the 5 components of the vestibular system?

A

1- peripheral receptor apparatus

  • in the inner ear
  • vestibular and cochlear share the same place

2- central vestibular nuclei
4 nuclei

3- vestibulo-ocular network
-horizontal gaze

4- vestibulospinal network
-posture and balance

5- vestibulo-thalmo-cortical network
-provide neck proprioception

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2
Q

what are the 2 types of movement?

A

angular –> semicircular canals –> CNS

linear –> saccule & utricle –> CNS

CNS–>
forebrain: perceived orientation
SC & cerebellum: postural control
oculomotor system: eye movements

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3
Q

where is the peripheral vestibular labyrinth (inner ear) located?

A

lateral and posterior to the cochlea

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4
Q

what is the peripheral vestibular labyrinth made up of?

A

1- bony labyrinth- several cavities in the petrous portion of the temporal bone

2-membranous labyrinth- resides in the bony labyrinth- fine membranes made up of a simple epithelium

  • specialized region= a sensory epithelium
  • filled with endolymph
  • surrounded with perilymph
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5
Q

what is perilymph?

A

fluid that fills the space between the bony labyrinth and the membranous labyrinth – protects

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6
Q

what is endolymph?

A

fluid fills the membranous labyrinth

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7
Q

what are the 2 main parts of the membranous labyrinth?

A

1- the static labyrinth

2-the dynamic labyrinth

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8
Q

what is the static labyrinth?

A

a pair of otolith organs

  • utricle (horizontal epithelium)
  • saccule (verticle epithelium)

maintain balance and equilibrium, eyes in horizontal gaze
only works in gravitational environment
linear acceleration

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9
Q

what is the dynamic labyrinth?

A

pair of 3 semicircular canals

  • anterior/superior
  • lateral/horizontal (angled up 30 degrees)
  • posterior

rotatory accelerations and decelerations
important in eye fixation with head movement (smooth pursuit)
doesn’t need gravity
works by inertia
works in outer space

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10
Q

what are the functions of the static labyrinth?

A

monitors the absolute position of the head in space
-assists in posture and balance

maintenance of eye position

perception- linear accelerations and decelerations

**needs gravity to work.

pitch and roll are static

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11
Q

what movement is pitch?

A

flexion/extension

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12
Q

what movement is roll?

A

lateral bend

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13
Q

what movement is yaw?

A

rotation

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14
Q

within the membranous labyrinth are 2 swellings:

A

utricle

saccule

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15
Q

what is a macula?

A

a specialized receptor within both the urtricle and saccule
horizontal orientation in the utricle
vertical orientation in the saccule

contains hair cells that synapse on the distal branches of the vestibular ganglion cells

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16
Q

what is a stereocilia?

A

the apical surface of each hair cell

17
Q

what is a kinocilium?

A

on one side of the stereocilia

18
Q

what is otoconia?

A

consists of calcium carbonate crystals

lies in a gelatinous substance that overlie the hairs

19
Q

what is striola?

A

a structural landmark consisting of small otoconia arranged in a narrow trench that divides each otolith organ

in the utricular macula, the kinocilia are directed toward the stroll

in the saccular macula, the kinocilia point away from the stroll

*note that given that the utricle and sacculus are on both sides of the body, there is a continuous representation of all directions of body movement

20
Q

what is an otolith?

A

group of otoconia together

21
Q

when hair cells bend stereocilia toward kinocilium..

A

the cell becomes depolarized

22
Q

what the stereocilia bend away from the kinocilia:

A

the cell becomes hyper polarized

23
Q

what are tonic labyrinth reflexes?

A

???

supine: extension of UE and LE
prone: flexion of UE and LE

sidelying:
extension of limbs touching floor
flexion of limbs facing up

trendelenburg positon:
UE: extension
LE: extension

24
Q

what are functions of the semicircular canals?

A

dynamic

  • enables us to track the rotation of the head in space
  • perception of angular acceleration and deceleration

important with eye fixation movement- eyes move first in a saccade and then the head turns

help with balance, equilibrium, maintaining tone in body

25
Q

if the anterior canal is stimulated on the R side then the :

A

posterior canal on the L side is inhibited

*horizontals work together

26
Q

each semicircular canal contains:

A

one enlarged end = ampulla

27
Q

what resides in the ampulla?

A

ampullary crest (crista ampullaris) a ridge that bears hair cells like those of the maculae

28
Q

what covers the ampullary crest?

A

cupula- a gelatinous capsule - extends upward to the roof of the ampulla

29
Q

when endolymph moves toward ampula it:

A

pushes against the cupola and bends the hair cells away which facilitates the system (depolarization)

30
Q

when endolymph moves away from the ampula it:

A

decreases AP (inhibits) because hair cells and cupola go the other direction

31
Q

what is the oculocephalic reflex?

A

doll’s eye maneuver

briskly turn head to one side or the other or tilt up and down

eyes turn in the opposite direction= intact BS pathway

32
Q

what are the clinical uses?

A

increase tone- phasic, quick movements

decrease tone- slow, rhythmic movements

autonomic responses
decreases in: BP, respiration, HR, body temp (by dilation of BVs)
Increases: peristalsis

33
Q

diseases of the vestibular system can take different forms and usually induce:

4 cardinal signs

A

vertigo
instability
nystagmus
often accompanied by nausea

34
Q

what are the most common diseases of vestibular system?

A

vestibular neuritis

benign paroxysmal positional vertigo (BPPV)

35
Q

what is benign paroxysmal positional vertigo (BPPV)?

A

pieces break off the otoliths slipped into one of the SSC

most cases it is the posterior canal

in certain head positions, these particles shift and create a fluid wave which displaces the cupola of the canal affected, which leads to dizziness, vertigo and nystagmus

Neuro (48 decks)

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