Vestibular System Flashcards
somatosensory system
1st line of defense against falls
- provides info about support surface (pressure receptors), body position, and movement (muscle/joint receptors)
Vestibular system
serves as an internal reference to determine appropriateness/accuracy of external sensory information
peripheral vestibular system components
semicircular canals
- anterior
- posterior
- horizontal
otoliths
- utricle
- saccule
semicircular canals
sense angular acceleration
semicircular canal functional pairs
right posterior/left anterior
left posterior/right anterior
both horizontal canals
*one is inhibited, one is excited
ampulla
base of SCC
Cupula
structure inside the ampulla that has hair cells/kinocilium imbedded in it
otoliths
sense linear acceleration
- utricle: horizontal movement
- saccule: vertical movement
otoconia
calcium carbonate crystals located in the inner ear—specifically in the utricle and saccule, that move on top of gel later to bend hair cells
central vestibular system components
vestibulocochlear nerve
vestibular nuclei
motor pathways
cerebellum
vestibular motor output systems
vestibular ocular reflex
vestibule spinal reflex
cervical ocular reflex
otolith ocular reflex
vestibulospinal reflex
maintains head and body equilibrium by facilitating or inhibiting skeletal muscle activity –> controls coordination for balance
cervical - ocular reflex
- signals head position on body
- maintains gaze stability
- taught as SUBSTITUTION for absent VOR
otolith ocular reflex
- input from otoliths, output to eye muscles
- controls horizontal and vertical eye movements via VOR
role of cerebellum in the vestibular system
- receives information directly from periphery as well as vestibular nuclei
- monitors and fine tunes vestibular reflexes
How does the VOR work?
maintains gaze stability during head motion thus controlling eye-hand coordination
- head moves one way, eyes move the other way
What direction foes the endolymph move in the RIGHT HSCC when you rotate your head to the right?
left
What direction do the hair cells move in the RIGHT HSCC when you rotate your head to the right?
TOWARDS the kinocilium –> excitation/AP
What direction does the endolymph move in the LEFT HSCC when you rotate your head to the right?
left
What direction do the hair cells move in the LEFT HSCC when you rotate your head to the right?
AWAY from kinocilium –> inhibition/hyperpolarization
how are the SCCs oriented inside your head?
anterior: sagittal plane - flex/ext
posterior: coronal plane - side bend
horizontal: transverse - rotation
gravity dependent position for the horizontal SCC
30 degrees cervical flexion
-makes the canals truly horizontal
gravity dependent position for the posterior SCC
Supine, head turned 45° to side
gravity dependent position for the anterior SCC
Supine, head extended backward
what is affected with a peripheral and central vestibular dysfunction?
affects sensation and perception of movement information
what are the 3 main types of peripheral vestibular dysfunction
1: Benign Paroxysmal positional vertigo
2: neuritis/labyrinthitis
3: hypofunction
Benign Paroxysmal positional vertigo
otoconia become dislodged from utricle / saccule and are displaced into the SCC –> affects flow of endolymph –> deflection of cupula
–> nerve signal –> vertigo
sign: nystagmus
what are the 2 types of Benign Paroxysmal positional vertigo
cupulolithiasis
canalithiasis
cupulolithiasis
- otoconia adhere to cupula –> constant firing –> immediate onset and persistent firing
canalithiasis
- otoconia free float in PSCC –> fluctuating vertigo and late onset
Vestibular neuritis
NO HEARING LOSS
- inflammation of vestibular nerve –> vestibular hyper stimulation –> vestibular hypofuncton
- hallmark: DIRECTION fixed nystagmus
vestibular labyrinthitis
HEARING LOSS/TINNITUS
-inflammation of inner ear (labyrinth) –> vestibular hyper stimulation –> vestibular hypofuncton
- hallmark: DIRECTION fixed nystagmus
peripheral vestibular hypofunction
damage to inner ear/vestibular nerve –> diminished/weaker neurological signal –> affects VOR/VSR
nystagmus
non-voliuntary rhythmic oscillation of eyes with clearly defined fast and slow components beating in opposite directions
- can be physiological or pathologicwh
4 types of pathologic nystagmus
spontaneous
positonal
gaze evoked
congenital
spontaneous nystagmus
due to central/peripiheral vestibular problem
positional nystagmus
can be paroxysmal or static
- torsional/rotatory nystagmus
- downbeat/upbeat nystagmus
torsional/rotatory versus downbeat/upbeat nystagmus
torsional/rotatory: PERIPHERAL dysfunction
downbeat/upbeat nystagmus : CENTRAL dysfunction
gaze evoked nystagmus
eye drift toward center, constant corrective saccades to reset gaze
congenital nystagmus
since birth
peripheral versus central nystagmus
peripheral: DIRECTION fixed, fatiguable
central: direction CHANGING, constant, smooth pursuit, saccades
