Vestibular System Flashcards
3 inputs for posture
somatosensory
vision
vestibular
what is the fastest sense + first line of defense against falls
somatosensory
optic nerve’s role in balance
visual proprioception
- allows us to orient ourselves in space
CN3 controls which eye muscles
medial, superior, and inferior rectus
CN4 controls which eye muscle
superior oblique
CN6 controls which eye muscle
lateral rectus
motor vision CNs
3,4,6
3 functions of motor vision
oculomotor eye control
gaze stability
vestibular ocular reflex (VOR)
VOR
stable vision while head is moving around
what type of information does the vestibular system provide the CNS
static vs dynamic positions of the head
3 factors that postural control depends on
individual info
environmental info
motor strategies for balance
how does VOR work
R head turn + L endolymph/hair movement
this excites the R horizontal canal + inhibits the L
when the head is turning to the RIGHT while the eyes stay in place, which eye muscles are responsible for keeping the gaze straight?
LEFT lateral rectus and RIGHT medial rectus
how are the crista, cupula and ampulia related
cupula is inside of crista + crista is located IN the ampulia
what is the tallest hair cell called
kinocilium
movement away from kinocilium causes ________ and movement toward it causes ______
deactivation
activation
3 planes of movement do the SCCs detect
YAW (no)
PITCH (yes)
ROLL
what do the semicircular canals sense
angular acceleration
what plane(s) of movement does the horizontal canal detect? how about posterior? anterior?
horizontal: YAW – “no”
ant/post: PITCH (yes) + ROLL
functional pairs of the SCCs
R post w/ L ant
L post w/ R ant
horizontal L/R
with a LEFT head turn:
1. where does endolymph go
2. where do hair cells go
3. which side is activated/deactivated
- right
- R goes toward kinocilium, L goes away from kinocilium
- left side activation, right side deactivation
utricle function
senses horizontal movement
saccule function
senses vertical movement
the utricle + saccule make up the….
otoliths
the otoliths sense…
linear acceleration
what sits on top of gel to bend hairs in inner ear?
otoconia
what vestibular nuclei have the orgin of the medial vestibulospinal tract? how about the lateral vestibulospinal tract?
medial + inferior nuclei
lateral nucleus
what is the relay center for ocular reflexes?
superior vestibular nucleus
what monitors and fine tunes the vestibular reflexes?
cerebellum
what structure assists in VOR stability
Semicircular canals
what reflex maintains head and body equilibrium to control coordination for balance
vestibulo-spinal reflex (VSR)
what happens during the cervical-ocular reflex (COR)
head and neck turn with the eyes to maintain gaze stability
what reflex is a substitution for VOR
Cervical-ocular reflex (COR)
otolith-ocular reflex (OOR)
inputs from otolithis –> output to eye muscles
controls horizontal and vertical eye movement via linear VOR
what SCC is most commonly affected in BPPV? why?
posterior SSC bc the otoconia “fall back” into it
BPPV symptoms
10-60 seconds of vertigo with changes in head position against gravity
what is the biggest BPPV sign
nystagmus
how do you know if nystagmus is for Posterior SCC
has upbeat + rotary component
how does cupulolithiasis vs canalithiasis occur
cup = otoconia adhere to cupula, making it much more dense
cana = free floating otoconia
cupulolithiasis symptoms
immediate onset + persistence of vertigo/nystagmus for as long as the head is held in the provoking position
canalithiasis symptoms
latent onset of vertigo and nystagmus but it disappears within 1 minute after otoconia have settled
neuritis vs labyrinthitis
N = no hearing loss bc only vestib nerve is inflammed
L = hearing loss and tinnitus bc whole structure is inflammed
what causes 98% of neuritis and labyrinthitis cases?
viral infections
are symptoms of neuritis/labyrinthitis sudden or gradual?
sudden
what is the hallmark diagnosis of vestibular neuritis/labyrinthitis
direction fixed of nystagmas
what is peripheral vestibular hypofunction
basically a basket term for anything other than BPPV
(damage to inner ear or vestib nerve that results in a weaker neuro signal)
how does neuroplasticity play a role in peripheral vestibular hypofunction unilaterally vs bilaterally
uni = can adapt
bi = substitutions
basic symptoms of peripheral vestibular hypofunction
VOR and VSR affected, gaze instability, motion sickness, oscillopsia, dizziness
physiologic vs pathologic nystagmus
physiologic = induced by normal stimuli
pathologic = abnormal + can appear with or without stimulation
4 types of pathologic nystagmus
spontaneous
positional
gaze evoked
congenital
spontaneous nystagmus is due to
central or peripheral vestibular problems
2 types of positional nystagmus
torsional/rotary
downbeat/upbeat
what does torsional/rotary nystagmus indicate
peripheral (BPPV) or brainstem dysfunction
what does downbeat/upbeat nystagmus indicate
central (cerebellar) dysfunction or could be peripheral (non-BPPV)
gaze evoked nystagmus
eyes drift toward center + a constant corrective saccade is used to reset gaze
nystagmus caused by peripheral vestib issues present like…
slow phase = VOR
fast phase = corrective saccade
when gaze goes toward fast phase, the nystagmus increases in intensity
ex: slow drift right + fast reset to left (L nystagmus)
nystagmus caused by CNS issues present like….
smooth pursuit with saccades
direction changing (usually following gaze)
how is nystagmus best examined
frenzel or infared video goggles
alexandar’s law
when gaze goes toward fast phase, the nystagmus increases in intensity
