Vestibular System Flashcards by Chavez Girls

somatosensory system

1st line of defense against falls
- provides info about support surface (pressure receptors), body position, and movement (muscle/joint receptors)

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Vestibular system

serves as an internal reference to determine appropriateness/accuracy of external sensory information

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peripheral vestibular system components

semicircular canals
- anterior
- posterior
- horizontal

otoliths
- utricle
- saccule

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semicircular canals

sense angular acceleration

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semicircular canal functional pairs

right posterior/left anterior
left posterior/right anterior
both horizontal canals

*one is inhibited, one is excited

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ampulla

base of SCC

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Cupula

structure inside the ampulla that has hair cells/kinocilium imbedded in it

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otoliths

sense linear acceleration
- utricle: horizontal movement
- saccule: vertical movement

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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

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central vestibular system components

vestibulocochlear nerve
vestibular nuclei
motor pathways
cerebellum

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vestibular motor output systems

vestibular ocular reflex
vestibule spinal reflex
cervical ocular reflex
otolith ocular reflex

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vestibulospinal reflex

maintains head and body equilibrium by facilitating or inhibiting skeletal muscle activity –> controls coordination for balance

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cervical - ocular reflex

signals head position on body
maintains gaze stability
taught as SUBSTITUTION for absent VOR

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otolith ocular reflex

input from otoliths, output to eye muscles
controls horizontal and vertical eye movements via VOR

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role of cerebellum in the vestibular system

receives information directly from periphery as well as vestibular nuclei
monitors and fine tunes vestibular reflexes

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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

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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