Neuro- vestibular system Flashcards
the vestibular labyrinth is restricted to the ________
membranous labyrinth
what is the vestibular labyrinth filled with?
endolymph
what are the 2 subdivisions of the vestibular labyrinth?
1) otolith organ
2) semicircular canals
what 2 structures make up the otolith organ?
a) Utriculus
b) Sacculus
The neuroepithelium of the otolith organ is the _____
macula
______ are imbedded in the macula
otoliths
the otolith organ is known as the “_______ labyrinth”, while the semicircular canal is known as the “______ labyrinth”
otolith- static labyrinth
semicircular- dynamic labyrinth
the semicircular canals are continuous with the cavity of the _______
utricle
what part of the semicircular canal contains neuroepithelium?
the Ampulla
the opening of the canals- holds the crista ampullaris
the neuroepithelium of the semicircular canals is called the what?
crista ampullaris
the gelatinous ______ of the crista ampullaris floats in endolymph
cupula
the membranous labyrinth is suspended within the _____________
osseous labyrinth
the osseous labyrinth is filled with _______, while the membranous is filled with ______
osseous= perlymph
membranous= endolymph
what range of vibrations can the otolith organ sense?
0-1 Hz
the otolith organ is responsive to _____ acceleration
linear
like an elevator
the static labyrinth is activated when the head ________
tilts
what happens in the static labyrinth when the head is tilted?
the otoliths embedded in the macula will deflect the hairs (stereocilia) of the hair cells
the hair cells of the static labyrinth are _______ sensitive. what can they measure?
- directionally sensitive
- measure direction and amplitude
the dynamic labyrinth consists of what?
3 pairs of semicircular cells
what is another name for the dynamic labyrinth?
semicircular canals
the semicircular canals sense ___________
turning movements of the head
the semicircular canals are sensitive to what range of vibrations?
1-10 Hz
higher freq than otolith organ
the canals of the dynamic labyrinth specifically respond to _____ acceleration
angular
what is the primary function of the dynamic labyrinth (semicircular canals)?
provide reflex control of eye movement
T/F: the endolymph of the semicircular canals is constantly moving
False- does not move when head is at rest
function of the semicircular canals: when the head turns, the \_\_\_\_\_ will deflect while the \_\_\_\_\_ remains stationary
cupula of the crista ampullaris deflects
endolymph remains stationary
when the cupula deflects, _____ fibers fire
afferent
the hair cells of the crista ampullaris are _____ sensitive
directionally
when the head moves toward midline, the hair cells of horizontal semicircular canals will ______ their firing rate
increase
when the head turns, the ______ on one side deflect toward midline, while the ______ on the opposite side deflects away
cupula
T/F: deflecting the cupula away from the midline will decrease the firing rate of hair cells
true
turn your head to the right. what happens to the cupula on the right side of the head? what does this cause?
cupula on right will deflect medially
- this increases the firing rate of the crista ampullaris
the eye responds via the ____-_____ to deflect the eye based on info from semicircular canals
vestibulo-ocular
the Doll’s Eye Phenomenon is a measure of what?
the function of vestibulo-ocular reflex arc
during the doll’s eye phenomenon, what happens to the eyes?
they move in response to movement of the head
T/F: the eyes move in the same direction as the head during the doll’s eye phenomenon
false- they move in the opposite direction
name the path of the ascending vestibular projections
-Medial longitudinal fasciculus = the pathway
final destination:
- Pontine tegmentum
- cerebellum
what are the ascending vestibular projections responsible for?
Eye movement control
from CEREBELLUM down to the eye muscles
where do the descending vestibular projections go?
spinal cord
what do the descending vestibular projections control?
antigravity muscles
the eyes can move only so far in the _____
orbit
when the eyes reach a certain point, they do what?
reset their position
T/F: the velocity of the eyes resetting is very fast
true
what is Nystagmus?
oscillating eye movements
the _____ system is responsible for the slow component of Nystagmus
vestibular
the fast components of Nystagmus cause what?
resetting of the eye
water or air introduced into the external auditory canal will stimulate what?
neuroepithelium of the ampule
-horizontal semicircular canal
what happens to the eyes during the caloric test?
moving horizontally (slow phase)
snapping back quickly (fast phase)
what does the acronym COWS stand for?
Cold opposite, warm same
what will happen to the subject during the caloric test?
they experience the illusion that the room is rotating around them
T/F: if cold water is used for the caloric test, the fast phase will be in the opposite direction
true
where is the vestibular cortex found?
posterior insular cortex
Name the brain structure in which primary afferents of the semicircular canals and otolith organ terminate.
Terminates in the pontine tegmentum & cerebellum
Within which region of the pontine tegmentum/cerebellum do the eye-movement controlling fibers terminate?
vestibular nuclei
Name the myelinated pathway that links the vestibular nuclei with the eye movement-control nuclei
Medial longitudinal fasciculus
connects vestibular nuclei with abducens nuclei
What is the location of the primary vestibular cortex?
Posterior insular cortex
-part of the parietal lobe
The vestibulo-ocular reflex is normally inhibited by the _________
cortex
