Foundational Information Flashcards
Vestibular System
-Provides CNS info about position of head and motion of the head
-Provide stable vision while head is moving
-Serves as an internal reference
-Postural stability
Vestibular Pathway
CN 8 > Vestibular nuceli/ Cerebellum/Vestibulospinal tract/Vestibuloocular/
Central Vestibular System
CN 8 > vestib nuclei > cerebellum/vestibulospinal/abducens/oculomotor
Peripheral Vestibular System
-Vestibular Apparatus
-Semicircular Canals
-Otolithic Organs
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 the rate of fluid changes when at rest and with head mmts to give information about the body in space
-only actively move during rotation of head in the opposite direction
-Only angular or rotational movement
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 from kinocilium (inhibiting)
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 stimulate neurons
-linear movement of the head
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 horizontal and vertical eye mmts
-via linear VOR
Vertigo
-sensation of the room spinning
BPPV or non-BPPV (anything not canal related)
Benign Paroxysmal Positional Vertigo: BPPV
-BPPV
-most common; age, trauma
-crystals from utricle or saccule (MC) fall from utricle into SCC (PSCC MC)
-heavy crystals cause change in endolymph viscosity and fire nerve signals
-top shelf vertigo
-brief vertigo and nystagmus
s/s:
-short spells, recurring
-holding still makes it better
Nystagmus: PNS
Peripheral Vestib:
-Slow phase: VOR
-fast phase: corrective saccade
-usually horizontal
-moves in the same direction
Nystagmus
-non voluntary rhythmic oscillation of eyes
-named by fast phase
-can be suppressed by fixation
-viewed with frenzel or infared goggles
-increases toward fast phase (Alexander’s law)
Physiologic: normal stimuli
Pathologic: abnormal; 4 types
Caused by vestib:
-slow phase caused by VOR
-fast corrective by cerebellum
Caused by CNS:
-smooth pursuit and saccades
Benign Paroxysmal Positional Vertigo: Canalithiasis
Canalithiasis (MC):
-otoconia fall off and free float in PSCC
-latent onset of vertico and nystagmus after provoking
-disappears in 1 min
s/s:
-short spells, recurring
-holding still makes it better
Benign Paroxysmal Positional Vertigo: Cupulolithiasis
Cupulolithiasis:
-otoconia fall off and adhere to cupula of PSCC making cupula denser around endolymph
-immediate vertigo is persistent until head moved
-nystagmus
s/s:
-short spells, recurring
-holding still makes it better
Nystagmus: CNS
CNS:
-smooth pursuit and saccades (cerebellum and brainstem)
-often follows gaze
-typically vertical, constant (not changed by fixation)
-changes direction when looking changes
Nystagmus: BPPV
BPPV:
-named by torsion (canal) and rotary component toward the lesion
-Upbeat and rotary for PSCC
-direction fixed
Cause:
-canal stimulation and mixed matched
Neuritis/Labyrinthitis
Neuritis: no hearing loss
Labryrinthitis: hearing loss and tinitis
-infection/inflammation causing hyperexcitation
-damage causes hypofunction
-fireing rate affected
-long lasting 3-7d
-nystagmus fixed on good side in all 3 degrees of gaze
s/s:
-sudden, lasting days, single event
-spontaneous, exacerbating by movement
