Vestibular System Flashcards
Bony labyrinth and what’s in it
Central vestibule and semicricular canals
Periplymph fluids (High in Na and low in K)
Membranous labyrinth
Utricle and saccuole (in the vestibule)
Ampulla at the base of the canals
Crtiae ampularis in the smeicircular canals
Endolymph (high in K and low in Na)
Sensory epithelium of vestibule
Sterocilia that lead to a kinocilum (surrounded by endolymph)…held together by tight junctions to the supporting cell
Activation of hair cells
As they swing toward kinocilia, depolarization and excitation…away leads to decreaksed impulse frequeny and inhibition
Depolarization due to K
Utricle and saccule structures
Sensory organ is called macula
Hair like stereocilia surrounded by gelatinous later with otoconia/otoliths that amplify system
Utricle vs. saccule
Utricle - horizontal plane (acceleration of a car or head tilt)
Saccule - verticle plane acceleration/deceleration
Canals
Horizontal senses changes in ortation
Anteior and posterior sense a somersault
Semicirculart canal sensory organs
Crista ampullaris
Hs a cupula that acts as a sail and allows the endolymph to flow through it (continuously)
Stages of semicircular canal sensation
1) Beginning of rotation when endolymph is lagging and rotating opposite relative to head…increased frwueny
2) Equilibrates and at a resting potential so it seems like movign at a contrant rate
3) Rotation stops and endolymph keeps going…seems like rotating the opposite way because decreased impulse fruny
Innervation of maculae and cristae
Neurons in vestbiular ganglion…target vestbular nuclei and the inferior cerebellum
Lateral and medial vestbiular nuclei
Lateral - lateral vestibulospinal tract
Medial - descending medial vestibulospinal and ascending in the MLF to gaze centers
VOR (head spinning left)
Keeps images from moving around the retina
If head rotation left, eyes gaze to right to try and maintain fixation
Left Vestbiular nuclei goes to right PPRF to abducens nuclei and uses same path as normal
On left, depolarized, on right, hyperpolarized
Occulocephalic reflex
DOll’s sign
Absence indicates injury to midbrain or pons
If you turn patients head from side to side, the eyes remain in fixed position (this is absence of sign)
Beating nystagmus
Right beating nystagmus
Left CN 8 lesion means that when sitting still, body is interpreting a right roation…this means that the eyes are gazing left and then snapping back to the right…only being controlled by right vestbiular nuclei that connects to left PPRF and activates left lateral rectus and right medial rectus
COWS
Cold water into right imitates a left head rotation so gets left beating nystagmus
Warm water into right imitates a right head roation so a right beating nystagmus
