Vestibular system

Question 1

what is the location and function of the peripheral receptor apparatus

Answer 1

located in the inner ear

transduction of head motion and position

Question 2

what is the location and function of the central vestibular nuclei

Answer 2

located in brainstem

integration/distribution of motor and spatial information

Question 3

what is the function of the vestibulocular network

Answer 3

control of eye movements

Question 4

what is the function of the vestibulospinal network

Answer 4

coordination of head movements, axial ms and postural reflexes

Question 5

what is the function of the vestibulothalamocortical network

Answer 5

perception of movement and spatial orientation

Question 6

where are vestibular receptors found

Answer 6

membranous labyrinth

Question 7

where is perilymph found

Answer 7

in the space between the bony and membranous labyrinths

Question 8

where is endolymph found

Answer 8

within the membranous labyrinth

Question 9

what structure senses rotational head movements

Answer 9

semicircular canals (aka ampulla)

Question 10

what structure senses translational head movements

Answer 10

otolith organs

Question 11

what innervates the receptor cells of the vestibular organs

Answer 11

afferent fibers of the vestibular ganglion

Question 12

what two arteries supply the labyrinth

Answer 12

labyrinthine artery (primary)
stylomastoid artery

Question 13

the labyrinthine artery is a branch of what

Answer 13

AICA

Question 14

what are the sxs of interrupted blood supply to the labyrinth

Answer 14

vertigo
nystagmus
unstable gait

Question 15

where are sensory receptors for the semicircular canals found

Answer 15

base of each ampulla

Question 16

how are receptors in the utricle oriented vs in the saccule

Answer 16

along the base of the utricle

along medial wall of the sacule

Question 17

what is the ductus reuniens

Answer 17

a duct connecting the saccule to the cochlea

Question 18

what is the cause of meniere’s dz

Answer 18

disruption of normal endolymph volume => distention of membranous labyrinth

Question 19

what are the sxs of menieres dz

Answer 19

occurs in unpredictable attacks of:
fluctuating hearing loss
vertigo
positional nystagmus
n/v
tinnitus

Question 20

how do you treat menieres dz

Answer 20

diuretic, salt restrictive diet

shunt into endolymphatic sac

Question 21

what is a kinocilium

Answer 21

a single longer cilia found on a hair cell

Question 22

how are type I hair cells characterized

Answer 22

chalice shaped

surrounded by nerve calyx

Question 23

how are type II hair cells characterized

Answer 23

cylindrical

Question 24

where are the cell bodies that control hair cell sensitivity via vestibular efferents

Answer 24

rostral to vestibular nuclei

lateral to abducens nucleus

Question 25

what CN activates the cell bodies that control hair cell sensitivity via vestibular efferents

Answer 25

V

Question 26

how are hair cells organized in the ampulla

Answer 26

embedded in crista type I in the center type II in periphery

Question 27

how are rotational head movement detected

Answer 27

endolymph is displaced => cupula and stereocilia displaced

Question 28

what is the cupula

Answer 28

gelatinous structure enveloping the ampulla

Question 29

what is the otolith memrane

Answer 29

a gelatinous coating in the macula which hair cell stereocilia extend into

Question 30

what is otoconia

Answer 30

calcium carbonate crystals covering the otolith membrane in the macula

Question 31

what role do otoconia play in sensation of linear acceleration

Answer 31

they are displaced in respose to linear acceleration => bend underlying hair cell stereocilia

Question 32

where do primary afferents of the vestibular nuclei enter the brainstem

Answer 32

pontomedullary jxn

Question 33

to what nuclei do afferents from the ampulla project

Answer 33

superior and medial vestibular nuclei

Question 34

to what nuclei do afferents from the maculae project

Answer 34

lateral, medial and inferior vestibular nuclei

Question 35

to what nuclei do afferents from the saccule project

Answer 35

contralateral oculomotor nucleus => infulence vertical eye movements

Question 36

to what cerebellar nuclei do the vestibular nuclei send afferents

Answer 36

dentate and fastigial nuclei

Question 37

what do vestibulovestibular fibers do

Answer 37

arise from vestibular nuclei and form connections with analogous contralateral nucleus

Question 38

what do spinovestibular fibers do

Answer 38

arise from all levels of SC => provide proprioceptive input to medial and lateral vestibular nuclei

Question 39

what does the vestibuloocular reflex do

Answer 39

stabilize eye movements, allowing you to keep fixed gaze when head is moving

Question 40

vertical eye movements are controlled by what vestibular structures

Answer 40

vertical semicircular canals and saccule

Question 41

horizontal eye movements are controlled by what vestibular structures

Answer 41

horizontal canals and utricle

Question 42

torsional eye movements are controlled by what vestibular structures

Answer 42

vertical semicircular canals and utricle

Question 43

a leftward head turn stimulates the left vestibular nuclei to facilitate contraction of what two muscles

Answer 43

right lateral rectus | left medial rectus

Question 44

what reflex elicits oppositely directed vertical eye movements when walking or running (to stabilize gaze)

Answer 44

linear vestibuloocular reflex

Question 45

cold water in the external auditory canal should cause what

Answer 45

nystagmus beating away from ear w/ water (COWS: cold water/opposite warm water/same)

Question 46

in what nuclei are neurons of the lateral vestibulospinal tract

Answer 46

lateral and inferior vestibular nuclei

Question 47

where do LVST fibers project

Answer 47

to all levels of ipsilateral SC via lateral medulla and anterior funiculus

Question 48

where do LVST fibers terminate

Answer 48

alpha and gamma motor neurons and interneurons in laminae VII-IX

Question 49

what is the function of the vestibulospinal network

Answer 49

influence of muscle tone and reflexive postural adjustments

Question 50

in what nuclei are neurons of the medial vestibulospinal tract

Answer 50

medial vestibular nucleus | lesser from inferior and lateral vestibular nuclei

Question 51

where do MVST fibers project

Answer 51

bilaterally through medial longitudinal fasciculus of the cervical SC

Question 52

where do MVST fibers terminate

Answer 52

laminae VII-IX of the cervical SC

Question 53

what is the function of the MVST

Answer 53

stabilization of the neck (AKA vestibulocolic reflex)

Question 54

what two areas of the primary somatosensory cortex receive vestibular signals

Answer 54

2v and 3a

Question 55

what does vestibular stimulation of area 2v do

Answer 55

produce sensation of whole body motion

Question 56

what does vestibular stimulation of area 3a do

Answer 56

integrate motor control of head and body

Question 57

what does vestibular stimulation of area 7 of the parietal cortex do

Answer 57

integrate cues of body motion in space (aka spatial awareness)

Question 58

what does vestibular stimulation of the lateral sulcus and PIVC (parietoinsularvestibular cortex) do

Answer 58

respond to body motion, somatosensory and visual stimuli

Question 59

what does vestibular stimulation of the prefrontal cortex and superior frontal gyrus do

Answer 59

controls smooth pursuit eye movements and saccades

Question 60

what is subjective vertigo

Answer 60

pt experiences sensation of spinning while surroundings are not moving

Question 61

what is objective vertigo

Answer 61

sensation of objects spinning while patient is not moving | -pt will have nystagmus in opposite direction of rotation

Question 62

what is the most accepted explanation for benign paroxysmal positional vertigo

Answer 62

otoconia become lodged in cupula of semicircular canal (cupulolithiasis) => abnormal cupula deflection when head changes postion

Question 63

where are vestibular schwannomas typically located

Answer 63

cerebellopontine angle

Question 64

what structures are impinged by a vestibular schwannoma

Answer 64

those traveling in the internal acoustic meatus - CN VII and VIII - labyrinthine a

Question 65

how do patients with a vestibular schwannoma usually present

Answer 65

with hearing loss, tinnitus and unstable gait

Question 66

what are the sxs of vestibular neuritis

Answer 66

severe vertigo n/v no hearing loss/CNS deficits