The Vestibular System

Question 1

reason for system

Answer 1

which way is up

where am i going

Question 2

contributes to ….

Answer 2

keeping eyes still as we move

maintiaing upright posture - intrinsically linked to cerebellum - motor output to posture muscles

Question 3

anatomy

inner ear

Answer 3

semicircular canals - head rotation

• anterior and posterior = moving up whilst spinning
• horizontal = spinning around

Question 4

anatomy

ampulla

Answer 4

wide openings at end of senicircular canals

mechanoelectrical machinery - hair cells of vestibular system

Question 5

anatmony

otolith organs

Answer 5

linear motion
utricle - car acceleration
saccule - vertical plane acceleration

Question 6

inside vestibular system

Answer 6

semicircular canal = filled with endolymph, either side = perilymph
utricle and saccule = endolymph

Question 7

hair cells

Answer 7

sensory receptors
same as auditory system - but respond to lower frequencies (0-50Hz)
at rest a few channels are open
structural differences = more clumped together, more rows

Question 8

kinocillium

Answer 8

involved in setting polarity of hair bundle

vestibular system keeps this throughout life vs cochlea cells dont

Question 9

2 types of hair cell

Answer 9

II - normal synapse

I - calyx synapse - covers all of bottom of hair cell = different communication with neuron

Question 10

detecting head tilts and linear acceleration

Answer 10

saccule and utricle
sensory patches - macula, hair cells found here
has line where hair cells are orientated in different ways
vs in audio system all hair face same way

Question 11

on top of hair cells =

Answer 11

otolithic membrane
gelatinous membrane with calcium crystals on top (otoconia) = adds weight
gravity pull otoconia when we move which drags membrane with it and so pulls hair cells = shuts or open channels

Question 12

ampulla

Answer 12

hair cells sit in middle and project up into cupula

cupula = gelatinous structure penetrated by hair bundles

Question 13

semicircular canals detect angular acceleration (rotation)

Answer 13

inertia of endolymph during rotation displaces cupula
work in pairs - turn to left = endolymph moves right in both canal sides = stimulation in one side and inhibition on other due to orientatin of hair cells
taller stereocilia both point to front to get different outcomes

Question 14

vestibular nerve and central pathways

Answer 14

vestibular organs ----- vestibular nuclei in brainstem ----- can communicate with:
cerebral cortex - perception
reticular formation - visceral response
oculomotor nuclei - eye muscles
spinal cord - balance
cerebellum - motor coordination

Question 15

vestibular - ocular reflex

Answer 15

shaking head vs shaking paper

activated hair cells = communication with brainstem - connect to oculo nucleus - pulls eyes back to middle

Question 16

vestibular nastagmus

Answer 16

enables resetting of eye position during sustained head rotation
nystagmus = slow eye movement in one direction then quickly flick back
slow phase = rotate in opposite direction to head movement
quick phase = rapid resetting back to centre