BMS11004 WEEK 9 - WEDNESDAY Flashcards
vestibular system, mechanoelectrical transduction, hair cells, CNS, vestibuloocular reflex
whats main role of vestibular system
balance
there are 3 sets of semicircular canals in each ear, name them
horizontal semi-circular, anterior vertical semi-circular, posterior vertical semi-circular
where are hair cells found in ear
at end of each semi-circular canal at widening called ampula
what is cupula (in ampula of semi-circular canals)
gelatinous structure penetrated by hair bundles
how do semicircular canals detect angular acceleration or rotation
endolymph has intertia (doesnt move as quick as hair cell) during rotation, displaces cupula
work in pairs on either side of head, one depolarised/other polarised to provide dual-feedback
as you move, endolymph moves into semicircular canal pushing against cupula, hair cell, cause signal to be sent
explain how semi-circular canals maintain balance if head turn right
endolymph fluid moves right, means pushed toward taller stereocilia so increased firing here, and less on right side
otolith organ (semi-circular canal) detects linear motion (moving horizontally, or in vertical plane up-and-down). how do the utricle, and saccule parts do this
detects if tilting head
utricle otolith organ- responsible for movements in horizontal plane (left, right, back, forth)
saccule otolith organ- responsible for movements in vertical plane
what does endolymph fill, what is its make-up
fills saccula, vestibuli, utricle, ampulla
high potassium
what does perilymph fill and what is its make-up
fills around endolymph filled spaces
normal extracellular solution with high NaCl sol
primary sensory receptors in vestibular system are hair cells. what 2 components do they have
hair bundles, with stereocilia and tip links
kinocilium throughout life (important for bundle developing at certain polarity)
explain why structure of vestibulo hair cell helps its action
more clumped hair cells, so can respond to different type of stimulus- bundles harder to move so better at responding to lower frequencies
why is cochlear inner hair cell adapted to its function compared to a vestibulo hair cell
responds to auditory stimuli so less clumped so can respond to different frequency types
mechanosensitive, respond to lower frequencies than auditory system (0-20Hz)
explain movement of hair bundles toward short/long stereocilia
when bundle is pushed toward taller stereocilia, depolarises (more positive) and increase AP frequency
if hair bundle move toward shorter stereocilia, reduce tension on tip link so shuts channel- more negative (hyperpolarisation) so less EPSP, less AP
what about tip links may cause hyperpolarisaiton to occur
resting tension causing it to be slightly open at rest
name 2 types of vestibular hair cell
type 1- large calyx, quite reliable synapse
type 2- normal sensory synapse
where are hair cells found
in sensory patch “macula”, on either side of striola (part of macula), running in different directions
how are hair cells moved
move in different directions if head moves in different directions
saccule and utricle detect head tile and linear acceleration/rotation
what is otolithic membrane
jelly like texture, sit on top of hair cell in macula
if tilt head to left, what happens to otholithic membrane and hair cell
otholithic membrane pulls to left and stimulates some hair cells (others get inhibited)
move to right, less pull and otholithic membrane move less quickly than hair cell but some hair cells are still stimulated and others inhibited
how does CNS tell us we stepped to right, not just tilted our head
visual system- look different
pull in neck muscle- proprioceptors
what is vestibular nystagmus
enable resetting of eye position during sustained head rotation
