what causes deflection of the cupula and cilia?
angular acceleration of the head causes endolymph fluid to lag behind, deflecting the cupula and cilia
what occurs if the cupula is pushed towards the utricle?
increase in firing rate
what occurs if the cupula is pushed away from the utricle?
decrease in firing rate
what are the otoconia?
crystals that sit on top of the gelatinous layer
what direction do utricle hair cells project, and what motion do they detect?
- vertical projection
- detects left/right/forwards/backwards
what direction do saccule hair cells project, and what motion do they detect?
- horizontal projection
- detects up/down movement
what is the striola?
- lines along which hair cells are oriented
- receptors on opposite sides are activated at different times, which offers another source of differential signals
where does the vestibulo-cochlear nerve (CN VIII) travel to?
to the ipsilateral vestibular nuclei
what are the four vestibular nuclei?
- lateral
- medial
- superior
- inferior
where do the medial and inferior vestibular nuclei project to?
the medial vestibulospinal tract (positioning of head and neck)
*plays an important role in vestibulo-collic reflexes
where does the lateral vestibular nuclei project to?
the lateral vestibulospinal tract (balance and extensor tone in limbs)
where do the superior and medial vestibular nuclei project to and via?
- projects to: oculo-motor nucleus, trochlear nucleus, amd abducens nucleus (together they help control eye position)
- via: the medial longitudinal fasciculus (MLF)
where do the vestibular nuclei direct also direct output?
- to the somatosensory cortex via the thalamus, for conscious perception of head movement
- to reciprocal projections with cerebellum, for balance, eye control, and movement coordination
what is the (likely) primary vestibular cortex?
operculum
what is the vestibulo-ocular reflex?
reflex that allows our eyes to fix on a target while our head moves
what causes nystagmus?
continual vestibular stimuli
what are three ways of measuring nystagmus?
- frenzel glasses
- electronystagmography
- video-nystagmography/video-oculography
what are tests for normal nystagmus?
- rotating chair test
- head impulse test
- caloric irrigation testing (COWS)
