Vestibular Flashcards
5 vestibular receptor organs
- Horizontal SSC
- Posterior SSC
- Anterior SSC
- Sacculus
- Utricle
3 relationships between SCCs and utricle
- at right angles to each other
- Anterior SCC is coplanar with contralateral Posterior SCC
- Horizontal SCC and utricle usually parallel with earth
Receptive area of SCC
ampulla
The thickened epithelium in the ampula is called
Ampullary crista
The ampulla contains
Culupa: gelatinous diaphram + hair cells within
What is displaced by endolymph current?
Cupula
Hair cells depolarize when they’re bent….
toward the kinocilium
K+ channels open and K+ flows in
Hair cells hyperpolarize when they’re bent…
away from the kincilium
Basolateral K+ channels open and K+ flows out
Physical relation of SCC kinocilium to utricle
Horizontal: kinocilium closer to utricle
Anterior & Posterior: kincilium on side farther from utricle
Horizontal SCC when head turns Left
Left depolarize
RIght hyperpolarize
Horzontal SCC when head turns Rights
Right depolarizes
Left hyperpolarize
Orientation of otolithic organs
Utricle: horizontal
Saccule: verticle
What does the otolithic membrane contain
otoliths/otoconia
macula that contain steriocilia
How does the utricle respond to head rotation?
It doesn’t
What direction polarizes otolith hair cells? Why?
Many different directions
Because the striola curves through the macula
What are the otoliths?
Calcium carbonate-protein granules
They give us info about gravity
What does the utricle determine?
Degrees of head tilting
What does the utricle determine?
Up and down/verticle movements of head
3 types of vestibulo-ocular reflexes and input and functions
Rotational:compensates for head rotation, from SCCs (yaw)
Translational: linear movement/pitch, Otoliths
Ocular Counter-Rolling: head tilt/roll, Otoliths
How do vestibular hair cells depolarize
Stereocilia toward kinocilium:
K in from endolymph
Ca flows in
After, K out into perilymph
How do vestibular hair cell hyperpolarize?
Sterocilia away from kincilium:
Basolateral K channels open
K flows out
3 limitations of vestibular system
- Not a perfect transducer of head mvmt
- Habituates
- Canals do not respond well to slow head movement
What assists vestibular system in limitation
The optokinetic system
What is the site of processing positional and movement info?
The 4 vestibular nuclei
SCCs project primarily to?
superior and medial vestibular nuclei
Cerebellar afferents to VN: NT? Controls?
GABA
Eye and head movement, posture
What provides proprioceptive input?
Spinovesitbular fibers
Inputs from where mediate info about head mvmt and vision?
Accessory optic system
Vestibulospinal reflexes do
reflexive postural adjustments of head and body
Lateral vestibulospinal tract:
From
Path
For
Lateral vestibular nucleus
Uncrossed and runs length of spine
Enables vestibular apparatus to influence ipsilateral prosimal limb muscles
