Vestibular System Flashcards
What are the five components of the vestibular system
peripheral receptor apparatus Central vestibular nuclei Vestibuloocular Network Vestibulospinal Network Vestibulothalamocortical Network
Characteristics of perilymph
Where is it found?
Less K+, more Na+
Bathes vestibular portion of CN VIII
Bony labyrinth
Characteristics of endolymph
Where is it found?
More K+, less Na+
Directly interacts with vestibular and cochlear cells
Membranous Labyrinth
Role of semicircular canals
How many are there?
Detect rotational movements
Anterior, Posterior, Horizontal
Role of Otolith Organs
How many are there?
Detect linear movements
Utricle, Saccule
What innervates the vestibular receptor organs
What gives blood supply to them?
Primary afferent fibers of vestibular ganglion
Labryinthine A. (Branch off AICA), and Stylomastoid A.
What connects the saccula to the cochlea?
Ductus Reuniens
Cause of Meniere’s Disease
Improper ion balance between perilymph and endolymph
Results in abnormal endolymph volume
Sx of Meniere’s Disease
Vertigo
Nystagmus
Nausea
Fluctuating hearing loss
Type I Hair cells
chalice shaped, surrounded by afferent terminal (nerve calyx)
Shorter than Type II
Type II Hair cells
longer
Cylindrical shaped
Steps that occur after rotational head movement occurs
Rotational Head movement Angular acceleration Endolymphe displaced Cupula is moved to one side or another Stereocilia is displaced in same direction as cupula
Towards kinocilium = depolarization of hair cell
Away from kinocilium = hyperpolarization of hair cell
Where is the superior vestibular nucleus found?
Supero-lateral in the central pons
Bordered by restiform body and 4th ventricle
Where is the medial vestibular nucleus found?
Lateral floor of 4th ventricle
Where is the lateral vestibular nucleus found?
Lateral to medial vestibular cells
*Contains Deiters cells (large neurons)
Where is the inferior vestibular nucleus
Extends through medulla, lateral to medial vestibular
What fibers travel through the juxtarestiform body?
Primary vestibulocerebellar Fibers
What vestibular receptors are used in vertical movements for the vestibuloocular reflex?
Vertical semicircular canals and saccule
What vestibular receptors are used in horizontal movements for the vestibuloocular reflex?
Horizontal semicircular canals and utricle
What vestibular receptors are used in torsional movements for the vestibuloocular reflex?
Vertical semicircular canal and utricle
During the Vestibuloocular reflex, what fibers are stopped from producing inhibitory signals on the IL abducens nucleus?
CL Commissural fibers
Caloric test
Put water in ear, should produce nystagmus
Cold water = Opposite side nystagmus
Warm water = Same side nystagmus
Positive Caloric Test
No nystagmus is produced IL
Fxn of the Vestibulospinal Network
influence muscle tone and reflexive postural adjustments
What areas of the vestibular cortex make up the primary somatosensory cortex
Areas 2v and 3a
Whole body motion
Area 7
parietal cortex
spatial/visual motion
Insular area of lateral sulcus, PIVC
Respond to body motion, proprioception, motion stimuli
Prefrontal cortex; superior frontal gyrus
Related to frontal eye fields
Control of saccades and smooth pursuit eye movements
