vestibular system Flashcards
where is the vestibular system located
inner ear
what does the vs process sensory info about
motion, head position, spatial orientation relative to gravity
the vs is responsible for what and what does it help stabilize
body’s equilibrium and helps stabilize gaze head and posture
what does the vs use hair cells to do
transduce physical motion into neural impulses
what 2 organs compose the vestibular labyrinth
otolith and semicircular canals
what are vestibular hair cells
flask shaped epi cells w a bundle of hair like processes attached btw each other by a tip link
whats sterocilia
hair like processes in hair cells
what is the name of the longest process in hair cells
kinocillium
when the stereocilia moves toward the kinocilium what happens
tip links are stretched and directly open K+ channels near the tips of sterocilia, allowing K+ to flow into hair cell down electrochemical gradient
depolarization (excitation)
the depo of the hair cell opens Ca2+ channels in cell body, allowing Ca2+ entry and release of NT to excite post-synaptic neuron (vestibular n.)
when the sterocilia moves away from the kinocilium what happens
hyperpolarization (inhibition)
what are the 2 otolith organs and what do they detect
utricle and saccule
linear movements (translational mvt and static head position relative to gravitational axis)
what does each otolith organ contain
sensory epi (macula) consisting of hair cells and supporting cells
gelatinous layer; hair bundles
fibrous layer: otolithic mem
embedded crystals of calcium carbonate: otoconia
what does otoconia do
makes otolithic mem heavier than the structures and fluids surrounding it
what happens after the head tilts or moves to generate a receptor potential
gravirty causes the mem to shift relative to macula, hairs in gelatinous layer are displaced and receptor pot is generated
describe utricle (position, what mvt does it detect give an example, where are the hair bundles directed and positioned)
horizontal position
detects horizontal translational mvts of the head
example: moving forward or backwards
hair bundles are towards striola and positioned more or less horizontally
describe saccule (position, what mvt does it detect, give an example, where are the hair bundles directed and positioned)
vertical position
detects vertical translational mvts of head
moving up and down
hair bundles are away from striola and more or less positioned vertically
what are the semicircular canals responsible for (for each)
responding to rotations of the head
horizontal: turning L and R (no)
sup: nodding up and down (yes)
post: tilting to a side (towards sh)
what are ampulla and what do they house
an enlargement at the base of each semicircular canal it houses the hair cells
what do the hair bundles extend out into in the semi-circ canals
a gelatinous mass: cupula
what circulates in the semi-circ canals
endolymph fluid
what happens after endolymph fluid mvt due to rotation of the head
endolymp pushes cupula and displaces hair bundles in same direction as head mvt
which depolarizes hair cell and
generates a receptor potential
electrical signal sent to brain
a tilt of the head to R side activates the hair cells in the ___ _____ canal but inhibits the hair cells in the ___ _____ canal
R horizontal
L horizontal
what rapid motor movements does the vs contribute to
reflexive eye mvt that stabilize gaze
rapid postural adjustements that maintain balance
higher order processes that are important to our sense of spatial orientation and self motion
is the central vestibular processing unisensory or multisensory and why
multisensory bc neurons in vestibular nuclei receive visual, cerebellar and proprioceptive m. inputs
the vestibular n. projects its fibers where
vestibular nucleus located in brainstem
what is the VOR
vestibuloocular reflex that produces eye mvt that counter head movements to permit the gaze to remain fixed on a particular point
what is VCR
vestibulocervical reflex that reg head position by reflex activity of neck m. in response to simulation of the semi-circ canals following head mvt
what is VSR
vestibulospinal reflex initiates another reflex the VSR that causes extension of forelimb and flexion of hindlimb to stabilize body and protect against a fall
the vestibulocerebellar pathways play a critical role in integrating and modulating vestibular signals to:
enable adaptive changes to the VCR
distinguish head tilts from translational mvt
distinguish passive mvt of the head and body from those that are self-generated
why does a person blindfolded on a rotating chair feel that the chair is slowing down and then stoping after 30 s even though its going at a cte velocity
during cte vel, firing rates of vestibular fibers that innervate the semi-circ canals return to baseline levels as the cupula return to its undeflected state
why does motion sickness by repeated mvts when travelling cause dizziness, nausea and vomiting
bc the brain receives conflicting info from the vestibular sys, eyes, m. n. the vs reports rocking back and forth while the car seems perfectly stable based on the visual and somatosensory info
what is oscillopsia
a person w vestibular damage finds it hard or impossible to fixate on visual targets while the head is moving
