Vestibular Flashcards
Vestibular system is an important source of
self motion and orientation information
Vestibular information influences
postural control and control of eye movement
Vestibular apparatus contains what type of receptors and what do they respond to (big picture)
sensory- respond to position of the head relative to gavity and to head movements
Information of the vestibular system is converted to neural signals that are converted by the ____ to the ___
vestibular nerve to the vestibular nuclei
Projectins from the vestibular nuclei contribute to what (what is the functin)
1 Sens info about head mvmnt and head position relative to gravity
2 Gaze stabilization
3 Postural adjustments
4 Autonomic function and consciousness
Semicircular canals get input about what
angular acceleration of the head
Saccule and utricle get input about what
linear acceleration of the head
head position relative to gravity
Semicircular canals and saccule and utricle input to what
vestibular nuclei
vestibulocerebellum
vestibular nuclei and
vestibulocerebellum output to where
Cerebral cortex
Oculomotor cortex
Spinal cord
Cerebral cortex gets info on what
perception of head orientation
Oculomotor nuclei gets ifo on what
eye movemnts
Spinal cord gets info on what
postural control
What other input besides vestibular information does the vestibular nuclei receive
vision
proprioceptive info
tactile info
auditory info
what inputs does vestibular info consist of
angular acc of the head
linear acc of the head
head position relative to gravity
receptors in semicircular canals detect movement of what and how
the head by sensing the motion of endolymph
Semicircular canals are made of
three hollow rings arranged perpendicular to each other
Each semicircular canal opens at both ends into the
utricle
Each semicircular canal has a ___ that contains a ___
ampulla that contains a crista
what is a crista
body of supporting cells and sesory hair cells
Hair cells are embedded in a gelatinous mass called the
cupula
Inside the utricle and the saccule is a receptor cell called
the macula
In the macula, hairs projecting from hair cells are embedded in gelatinous material - above the gelatinous materal are what
otoconia - small, heavy, sand like crystals
When the macula is moved into diff positions, the weight of the ___ bends the hairs and then what
weight of the otoconia bends the hairs
hair cells are stimulated
change the pattern of vestibular neuron firing
When the head is at rest or midline - what is happening
there is a spontaneous tonic discharge in the bilateral vestibular nerves (branch of CN 8)
When the head is at rest or midline - and there is equal tonic discharge on both sides what does this signal
no imbalance of the firing neurons signals that the head is not moving
Semicircular canals - each canal in a pair produces
reciprocal signals
inc signals from one canal occur simultaneously with dec signals from its partner
What happens if the signals from a pair of semicircular canals are not reciprocal
difficulties with control of posture, abnormal eye movements, nausea
where are the hair cells
in the ampulla crista
when the head mvoes the cupula is displaced by the flow of
endolymph
as the head turns, the hair cells on which side hyperpolarize and which depoliarize
the hair cells on the side away from the direction of the turn hyperpolarize (dec signals on that side) and the hair cells on the side toward the direction of the turn depolarize (inc vestibular nerve signals on that side)
because of inertia, rotation of the head in a counterclockwise direction causes the endolymph to move which direction
counterclockwise
clockwise with respect to the canals
Otolith organs are what
utricle and saccule
otolith organs are ___ __ within the vestibular system
membranous sacs
Otolith organs are not sensitive to
rotation
otolith organs response to
head position relative to gravity and to liner acceleration and deceleration
Inside an utricle and saccule is a
macula
Macula
hair cells enclosed by a gelatinous mass topped by calcium carbonate crystals
Otoconia are
calcium carbonite crystals that are more dense than the surround fluid and gelatinous support
Otolithic organs - changing head positions does what to he macula? and then what
tilts the macula
the weight of the otoconia displaces the gelatinous mass, bending the embedded hairs
What does bending of the embedded hairs do
stimulates or inhibits the hair cells depending on the direction of the bend
Otoliths - when the head is normal and upright in a neutral position, the macula in each left and right utricle is approximately
horizontal
any substantial linear horizontal acceleration will excite some hair cells in each utricle
Utricles are sensitive to
horizontal acceleration (going forward at a green light)
Saccules are sensitive to
vertical linear acceleration (elevator)
Central vestibular system stimuli include
angular acc of the head
linear acc of the head
head position relative to gravity
Central vestibular system receptros
semicircular canals
utricle and saccule
semicircular canal and utricle and saccule send their infor where
vestibular nuclei and vestibulocerebellum
Vestibular nuclei and vestibulocerebelum send their info where
vestibular cerebral cortex
oculomotor nuclei
spinal cord
Vestibular cerebral cortex gives output about
perception of head orientation
oculomotor nuclei gives output about
eye movements
spinal cord gives output about
postural control
Vestibular role in motor control -
gaze stabiliztion
postural adjustments
Vestibular role in motor control - gaze stabilization is operated by what
VOR
Vestibular role in motor control - postural adjustments are acheived by what
reciprocal connections between the vestibular nuclei and the spinal cord, reticular formation, superior colliculus, nucleus of CN 11, and cerebellum
What happens when we rapidly rotate out head by spinning around
altered postural control head orientation adjustments eye mvmnt reflexes autonomic changes conscious awareness of head orientation and movement
VOR functions to do what
stabilize visual image during head movements
VOR - eyes move in which directio
opposite to that of the head movement
what can supress the VOR
cerebellum
How does the VOR work
rotation acc or dec of the head receptors in semicircular canals vestibular nuclei ocular motor nuclei extraocular muscles
when would the VOR be suppressed by the cerebellum
when we want our gaze to follow the direction we are turning out head - redirecting our gaze
