Vestibular system function Flashcards
what occurs in the SC canals when the head is stationary
SC canal and endolymph fluid inside the canals isn’t moving
- hair cells afferents are firing at baseline
what occurs in the SC canals during head rotation
SC canal is rotated and endolymph fluid stays stationary
- fluid presses up against the cupula, deflecting it and the hair cells
- endolymph presses on the cupula in the opposite direction of mvmt
where is the axis of rotation of the SC canal
through the loop of the canal
what occurs during acceleration about the vertical axis
(yaw rotation)
- stimulates the horizontal canals
- doesn’t affect anterior or posterior canals
what occurs during acceleration about the back to front axis
stimulates the anterior and posterior canals
what occurs during acceleration about the ear to ear axis
stimulates the anterior and posterior canals
what occurs when the head is rotating at constant speed
endolymph fluid starts to move along with the skull
- no more deflection of the cupula (therefore resting rate of discharge)
what causes dizziness
deceleration
- endolymph starts to push again due to inertia from constant speed
what is the relationship between firing rate and acceleration
acceleration = increased firing rate
constant velocity = back to resting rate
deceleration = decrease in firing rate
why are SC canals biphasic
can code for acceleration and deceleration
what occurs in the otolith organs when the head is tilted or linerally accelerated
the mass of the otoconia under gravity pulls the otolithic membrane to the side which deflects the hair cells receptors
what occurs in the otolith organs with tilt
otoconia tilts with the head
what occurs in the otolith organs with forward acceleration
pulls otoconia backward
- reads the same as bwd tilt
what occurs in the otolith organs with deceleration
pulls otoconia forward
- reads the same as fwd tilt
can the vestibular system differentiate between tilt and linear acceleration
no - they read the same
what is the somatogravic illusion
quick linear acceleration in takeoff is read by otolith organs as backward tilt
- occurs without visual info to counteract
what is the response of vestibular hair cell receptors at rest
some stretch gated K+ channles are open
gives the afferent a background (spontaneous firing rate)
what is the response of vestibular hair cell receptors when the kinocilium is deflected AWAY from midline
more K+ channels open
increases inwards K+ current
further depolaires the hair cell
releases more glutamate
increases afferent firing rate
what is the response of vestibular hair cell receptors when the kinocilium is deflected TOWARDS the midline
closes K+ channels
decreases inwards K+ channel
hyperpolarises the hair cell
releases less glutamate
decreases afferent firing rate
why is endolymph a unique ECF in the body
K+ concen is higher than the Na+ concen
