Vestibular Function Lec28 Flashcards
Vestibulo-Ocular Reflex - maintains
steady gaze
Vestibulo-Ocular Reflex moves the eyes
opposite to head so they stay fixed on a point
Vestibulo-Colic Reflex - maintains
orientation of head and neck against gravity
Vestibulo-Spinal Reflex isn involved in ___ and ___
kinesthetic awareness, correction for stumbling.
The Vestibular System can detect (3)
rotation, translation, and gravity
The 3 semicircular canals sense
rotational movement/angular acceleration
The otoliths (utricle and saccule) detect ___-
translational movement/linear acceleration & gravity
where are hair cells found in the vestibular system
in 3 semiciruclar canals, otoliths
Utricle is oriented to sense ___ acceleration,
horizontal
Sacculus is oriented to sense ___ acceleration
vertical
The utricle and sacculus hair cells project into a gelatinous ___ with otoconia, calcium carbonate crystals which provide mass
“otolithic membrane”
Inertial forces on the head will displace the otolithic membrane and hair cells in the ___ direction
opposite direction
if hair bends towards kinocilia then __ occurs
cn 8 excitement, depolarization
if hair bends away from kinocilia then
hyperpolarization, cn 8 inhibitor
he 3 pairs of semicircular canals on each side of the head work
together Rotation in a particular direction will excite the hair cells of one canal and inhibit the hair cells in its partner.
All the hair cells in a canal’s ___ are oriented in the same direction
ampulla
All the hair cells in a canal’s are opposite of the ____
sterocilia in the paired canal
The ampulla of each canal has a gelatinous membrane called the ___
cupula
____ displaces endolymph –> which displaces the cupula.
Acceleration
Head rotation to face R. ____ the R. horizontal canal
excites
Head rotation to face R. excites the L. horizontal canal
inhbiits
VOR Rotation to the L. excites the
L. CN 8 & L. vestibular nuclei,
VOR The L. vestibular nuclei excite the ____
R. abduscens and left medial rectus
VOR L. vestibualr n. excites abduscens —> activates
right lateral rectus muscle
increased firing in one canal means the head is
rotating toward that side
Vestibular balance nystagmus – one side has less firing than the other, so the other side compensates
eyes move slowly to ___ of the decrease firing and then back to midlin
the side
he vestibular system is poor at detecting constant ___
velocity motion.
