4 - Vestibular Function Flashcards
what is the role of the vestibular system?
- detects forces generated by movement and translates this into a sense of balance
- provides info about the positon of the head in space
where is the vestibule located?
between the semi-circular canals and cochlea
what does the vestibule contain
utricle and saccule
the utricle and saccule have equilibrium receptors called what?
maculae
what does the saccule detect?
vertical acceleration/sensation of moving upwards
what does the utricle detect?
horizontal acceleration/moving forwards
what are the otolith organs?
utricle and saccule
what do the semi circular canals detect? what do the otolith organs detect?
semi-circular canals - angular acceleration
otolith organs - linear acceleration
what system do the semi-circular canals form? what system do the otolith organs form?
semi-circular canals - dynamic system
otolith organs - static system
what are otoconia?
calcium carboate crystals that form the striola which in turns rests on the otolithic membrane
how does the otolithic membrane detect changes in linear acceleration?
- head moves
- striola on otolithic membrane (gelatinous layer) moves
- creates sensory transduction
- bends hair cells embedded in the otolithic membrane
- creates senstation of acceleration
semi-circular canals are essential for the coordination of what organ?
the eyes
label which semi-circular canal is responsible for rolling, yawing and pitching:
how do the semi-circular canals detect angular acceleration?
- endolymph movement displaces cupula (gelatinous mass)
- causes physical strain on hair cells
- deflection towards the kinocilium increases firing, deflection away from the kinocilium decreases it
what is the kinocilium?
longest and thickest hair cells within the stereocilia
how is signal transduction controlled in semi-circular canals?
mechanically gated channels
what type of transmission occurs in the semi-circular canals?
glutamatergic
what is the purpose of the vestibulo-ocular reflex?
- prevents retinal slip
- as the head rotates left, the eyes rotate right etc
what is nystagmus?
repetitive and involuntary eye movements that alternate beween slow eye movement and rapid saccadic movement
what is slow phase eye movement mediated by?
vestibulo-ocular pathway
what is fast phase eye movement triggered by?
cerebral cortex
what phase eye movement is common in a comatose patient?
slow phase is present, but not fast phase
what is the role of the vestibulo-spinal tract?
basic balance and postural control
how do axons from the vestibular nuclei descend?
ipsilaterally
