Vestibular Flashcards
Inner Ear
Vascular structures
anterior inferior cerebellar artery
Branch of anterior inferior cerebellar artery:
internal auditory artery
Internal auditory artery separates into
Vestibular a.
Cochlear a.
Vestibular apparatus is made up of:
Utricle
Saccule
Semicircular canals
Stereocilia function
helps us hear and convert sound waves
Where can you find Perilymph?
Cochlea
Where can you find endolymph?
Semicircular canal
Conduction hearing loss
Impacted ear wax
Middle ear damage
Sensorineural hearing loss
Damage to hair cells of organ of corti
Damage to processes of cochlear division CN VIII
Congenital: most genetic
Congenital sensory nerve deafness is typically a
recessive trait
Common causes of conduction deafness may include:
Otosclerosis
Fluid in the tympanic cavity
Ruptured tympanic membrane
Sensorineural deafness results when
the transmission of nerve impulses is impaired.
Conduction deafness occurs when
the transmission of sound waves across the tympanic membrane through the ossicles onto the oval window is impaired
Vestibular system is essential for
postural control and for the control of eye movements.
Vestibular apparatus responsive to:
Position of the head relative to gravity
Head movements
how is Vestibular apparatus transduced?
Vestibular nerve
Vestibular nuclei (in the brainstem)
Flocculonodular (flocculus) lobe (smooth out head and eye movements)
semicircular canals are sensitive to which acceleration?
Angular acceleration
otolithic organs (saccule and utricle) are sensitive to which acceleration?
Linear acceleration in vertical and horizontal planes
Deflection toward the kinocilium activates
K+ channels causing depolarization of the synapse
Deflection away from the kinocilium
hyperpolarizes the synapse
The utricle detects linear accelerations and head-tilts in the
horizontal plane
The saccule detects linear accelerations and head-tilts in the
vertical plane
Benign Proximal Positional Vertigo (BPPV) cause
otoliths move into ampulla
Benign Proximal Positional Vertigo (BPPV) symptoms
will ALWAYS see rotational eye movements
Receptors in semicircular canals detect movement of the head by sensing the motion of
endolymph
Crista
consists of supporting cells and sensory hair cells
cupola
Hair cells are embedded in a gelatinous mass
If I turn my head to the R, which side gets depolarized and which side gets hyper polarized?
The R side gets depolarized and the L side gets hyper polarized
Saccule and utricle functions
linear acceleration and position of head relative to gravity
Projections from the vestibular nuclei contribute to:
Sensory information about head movement and head position relative to gravity
Gaze stabilization (i.e., control of eye movements when the head moves)
Postural adjustments
Autonomic function and consciousness
Vestibulo-ocular reflex (VOR)
Stabilizes visual images during head movements.
The primary function of the VOR is to control the eye position during head movements so as to maintain a stable visual image and therefore contribute to equilibrium
Example of Vestibulo-ocular reflex (VOR). Moving my head to the R
Signals from the right horizontal semicircular canal increase
Signals from the left horizontal semicircular canal decrease
Signals travel to vestibular nuclei and then CN nuclei
Activation of rectus muscles that move eye to the left
Inactivation of rectus muscles that move eye to the right
Three major planes of action of the vestibulo-ocular reflex
Yaw, Pitch and Roll
Yaw
horizontal rotation about the vertical z axis
Pitch
vertical rotation about the binaural y axis
Roll
vertical rotation about the x axis (“line of sight”).
A tone imbalance inyawindicates lesions of the
lateral medulla, including the root entry zone of the eighth cranial nerve and/or the vestibular nuclei.
A tone imbalance inrollindicates
unilateral lesions (ipsiversive at pontomedullary level
A tone imbalance inpitchindicates
bilateral (paramedian) lesions or bilateral dysfunction of the cerebellum, especially the flocculus.
Vestibular role in motor control, Two roles:
Gaze stabilization and postural adjustments
Two spinal tracts of postural adjustments
Lateral vestibulospinal tract and Medial vestibulospinal tract
Lateral vestibulospinal tract
Lower motor neurons to postural muscles in the limbs and trunk
Medial vestibulospinal tract
Adjust head position to upright
Vestibulocerebellum
Receives vestibular information
Influence postural muscles and eye movements
Can be mapped in the cerebellum
Six pathways associated with the vestibular nuclei function
help you stand up tall
