Vestibular System Flashcards
Provides sense of equilibrium
Fluid-filled sacs and ducts located in the temporal bone.
Hair cells in the otolith organs (utricle and saccule) respond to linear accelerations of head.
Hair cells of the ampullae in the semicircular canals respond to head rotations
Works closely with other sensory systems to maintain stable body position.
Vestibular System
within the membranous labyrinth is an extracellular fluid and is unusual because it contains a relatively high concentration of K+, but low levels of Na+ and Ca2+ ions.
Endolymph
Hair bundles project from the apical surface of hair cells into:
endolymph.
The basolateral hair cell membrane is bathed in ________ (regular extracellular fluid).
perilymph
Structure of Vestibular Organ
membranous labyrinth
3 perpendicular canals+, utricle,and saccule
+=rotation
*= linear accel
Hair cells in the otolith organs (utricle and saccule) respond to linear accelerations of head.
Hair cells of the ampullae in the semicircular canals respond to :__________
head rotations (angular acceleration).
Line of polarity reversal
In the utricle the axes of polarity of hair cells reverse direction along a central region of the epithelium called the striola.
In the saccule the hair bundles are oriented facing away from the striola.
In the utricle the axes of polarity of hair cells reverse direction along a central region of the epithelium called the striola.
In the saccule the hair bundles are oriented facing______ from the striola.
away
Endolymph moves the cupula and stimulates hair cells in the _______. Hair bundles within the canal all have the same orientation. Vestibular nerve carries signals to the brain.
crista ampullaris
Even at rest the vestibular nerve fires action potentials. During a rotation in the excitatory direction, firing rate will: ___
increase and then adapt (due to endolymph inertia)
cupula
Jelly like
providing the sense of spatial orientation. Located within the ampullae of each of the three semicircular canals.
the sensory organ of rotation located in the semicircular canal of the inner ear. The function is to sense angular acceleration and deceleration
crista ampullaris
Motion sensed by Cupula
Acceleration
Deceleration
Does not sense continued motion (Adaptation)
Ion channels (permeable to cations) are gated by _______ which connect adjacent stereocilia in the hair bundle.
tip links
At rest ~ 10 % of the mechano-sensitive channels are open.
Pushing the hair bundle in the excitatory direction (towards the tallest cilia) opens more channels, _________ from endolymph enter and depolarize the hair cell.
K+ and Ca2+
Hair Cells are mechano-transducers
Pushing the bundle away from the tallest cilia closes channels and __________the hair cell.
hyperpolarizes
Hair Cells are mechano-transducers
Vestibular Hair Cell Types
Type 1 and Type 2
Vestibular Ocular Reflex (VOR)
Shortest Reflex in body
Enables stable visual field during head movement
Oculomotor nuclei in brainstem
Leads to Nystagmus (involuntary eye movements)
During a head rotation the vestibular system signals how fast the head is moving and the oculomotor system responds to keep visual field stable.
Vestibular Ocular Reflex (VOR)
Movement of accessory structure modulates release of __________ from hair cells onto afferent nerve terminals.
glutamate
Vestibular neurons (VIIIth nerve) carry head velocity and acceleration signals to __________in the brainstem.
vestibular nuclei
Efferent fibers originate from _______- and synapse onto hair cells or their afferents. Efferent stimulation can excite or inhibit afferent firing.
brainstem
Vestibular Nuclei Subdivided into:
superior, medial, lateral, descending.
Vestibular Nuclei- Superior and medial receive fibers mostly from
semicircular canals (gaze control).
Vestibular Nuclei- Lateral nucleus (Deiter’s nucleus) receives input from canals and otoliths and is involved in:
postural reflexes.
Vestibular Nuclei- Descending nucleus receives mostly otolith input and integrates ____________
vestibular and motor signals
Angular accel mechanism
Cupula moves more quickly than endolymph (it is being dragged through) and bends Cilia on hair cells
bent towards kinocilium: depol/ excit
bent away: hyperpolar/ inhibit
Nystagmus
Head rotation causes eyes to move slowly in opposite direction
When limit of eye movement is reached, eyes rapidly snap back (nystagmus), then move slowly again
*occurs in the same direction of head movement
