Vestibular System Flashcards
Peripheral Vestibular System
-Vestibular Apparatus
-Semicircular Canals
-Otolithic Organs
Central Vestibular System
Pathways: vestib ganglion < vestib nuclei
-Medial longitudinal fasciculus
-Vestibulospinal tracts (med/lat)
-Vestibulocolic
-Vestibulothalamocortical
-Vestibulocerebellar
-Vestibulorecticular
Vestibulocerebellum
Vestibulocortex
Vestibib Nuc
Vestibular Apparatus
Semicircular Canals: ant, pos, horizontal
-each with an ampulla
Otolithic Organs: utricle, Saccule
Membranous Labyrinth
-separated by perilymph fluid
-filled with endolymph
-hair receptor cells bend with mmt
Semicircular Canals
-Ampulla that contains a crista with a cupula (gelatanous structure containing hair)
-hairs constanly fire AP when at rest and with head mmts to give information about the body in space
-only actively move during rotation of head
Horizontal: head rotation (no)
Ant and Post: pitch and roll (yes)
-R and L Posterior and anterior work in same plane
Ex: Turn to the L, L endolymph shifts toward kinocilium (activating), R endolymph shifts away froom kinocilium
Otolith Organs
Urtricle and Saccule: membranous sac that responds to linear acceleration/decceleration
-have a macula that contains hair cells embedded in a gelatinous mass with microscopic cristals (otoliths) on top
-displacement of otoliths sttimulate neurons
Uricle: Horizontal mmt
Saccule: vertical mmt
Cervical-Ocular Reflex
-postural adjustments of head in response to SCC
-substitution for VOR when absent
Vestibulo-Spinal Reflex
-postural tone and adjustments of the body for balance while maintaining equilibrium
Medial Longitudinal Fasciculus
-Bilateral connections to extraocular eye muscles and superior colliculus
Cerebello-Thalamocortical Pathways
-ascending pathway
-lateral and superior vestib colliculi < thalamus < posterior parietal cortex
Vestibular System Function
-provides CNS info of head and body
-stable visiono while head is moving
-internal refernce to determine appropriateness of sensory info
Vestibulo Occular Reflex
-head and eyes move in diff direction to maintain view
-opp lateral rectus activate to move eyes in same direction
Activation of hair cells
-movement that bends hair toward kinocilium causes depolarization and activation
-movement that bends hair away from kinocilium causes hyperpolarization and deactiviation
Otolith Ocular Reflex
-input from otoliths
-output to eye muscles
-controls horizoontal and vertical eye mmts
-via linear VOR
Benign Parooxysmal Positional Vertigo
-BPPV
-most common
-crystals from utricle or saccule (MC) fall into SCC (PSCC MC)
-cause change in endolymh viscosity and fire nerve signals
-brief vertigo and nystagmus
Canalithiasis (MC):
-otoconia fall off and free float in PSCC
-latent onset of vertico and nystagmus after provoking
-disappears in 1 min
Cupulolithiasis:
-otoconia fall off and adhere to cupula of PSCC making cupula denser around endolymph
-immediate vertigo is persistent until head moved
-nystagmus
Nystagmus
-non voluntary rhythmic oscillation of eyes
-named by fast phase
-can be suppressed by fixation
-viewed with frenzel or infared goggles
CNS:
-smooth pursuit and saccades (cerebellum and brainstem)
-often follows gaze
-typically vertical, constant
Peripheral Vestib:
-Slow phase: VOR
-fast phase: corrective saccade
-usually horizontal
BPPV:
-named by torsion (canal) and rotary component toward lesion
-Upbeat and rotary for PSCC
Physiologic: induced by normal stimuli; spinning
Pathologic: abnormal, 4 types
