Vestibular System Flashcards
What are the 3 systems that contribute to postural control?
- vestibular
- visual
- somatosensory
What are the fxns of the vestibular system?
- sense and perceive self-motion
- postural control
- stabilization of gaze
Stabilization of gaze involves the ________-________ reflex.
vestibulo-ocular reflex (VOR)
What are 3 elements to postural control?
- orient to vertical
- stabilize head
- control COM
Peripheral sensory apparatus components:
- 3 semicircular canals
2. otoliths
Central processor components:
vestibular nuclei
Motor output components:
- VOR (for gaze stability)
2. vestibulospinal (for posture/balance responses)
Name 3 broad components to vestibular system:
- peripheral apparatus
- central apparatus
- motor output
Peripheral vestibular apparatus and cochlea are imbedded in what bone?
petrous portion of temporal bone
What membrane lined chamber houses the vestibular apparatus and cochlea?
membranous labyrinth
The VISCOUS fluid that fills the membranous labyrinth chamber is:
endolymph
The fluid that fills the space between membrane and bone is:
perlymph
How many planes to the 3 semi-circular canals?
3 planes
anterior/posterior/lateral
All 3 semicircular canals open at both ends to the:
utricle
The extended portion at the end of each semicircular canal is the:
ampulla
The hair cell mechanism within the ampulla is called:
crista or “crist”
Crista hair cell receptors are covered by:
gelatinous cupula
The cupula is exposed it:
endolymph
Crista hair cell receptors have protruding _______.
stereocilia
The longest sterocilia are the _______, which are arranged in the same direction within each canal.
kinocilum
Semicircular Canals detect:
angular acceleration
What causes cilia on hair cells to bend?
due to viscosity, with head movement the endolymph lags behind and pushes cupula
What results in increased firing rate?
when stereocilia bend TOWARD kinocilum
depolarization (+) of hair cells occurs
What results in decreased firing rate?
when stereocilia bend AWAY FROM kinocilum
hyperpolarization (-) of hair cells occurs
Baseline firing rate is equal bilaterally at _____ spikes/sec.
80-100 spikes/sec
Receptor potentials summate in hair cells and cause:
neurotransmitter release at base of hair cell
AP generation in CN VIII
Describe the push-pull arrangement
equal and opposite response of complimentary canals (reciprocal signals)
ex: R rotation means increased firing of R lateral canal and decreased firing of L lateral canal
Head movement velocity is proportional to
firing rate of CN VIII
What two structures make up the otolothic organs?
saccule and utricle
Otoliths detect:
linear acceleration
static head position relative to gravity
Otolith orientation:
saccule = vertical utricle = horizontal
Otolithic receptor area is called:
macula
What makes otoliths sensitive to gravity?
calcium carbonate crystals called otoconia
What are the 4 vestibular nuclei?
- superior
- inferior (descending)
- medial
- lateral (deiter’s)
Info is conveyed from hair cells by vestibular portion of CN VIII to the ______:
vestibular nuclei
Describe central processing of vesicular nuclei?
- different nuclei have different afferent and efferent connections
- vestibular nuclei integrate visual and somatosensory info in addition to vestibular
Motor output goes down to SC via _______ and up to eye movement nuclei via ______.
down: vestibulospinal tracts
up: MLF (medial longitudinal fasiculus)
Symptomatology of vestibular dysfxn
dizzy light-headed vertigo disequilibrium oscillopsia
What is oscillopsia?
unstable, moving visual field
What is the term for abnormal sense of movement that occurs more with acute unilateral lesions?
vertigo (vertigenous)
Common tumor that influences vestibular system?
acoustic schwannoma
What are some influences that aging has on vestibular system?
vascular
neuropathy
central processing
stroke
