Vestibular System Flashcards
what are the vestibular sensory organs
semicircle canals and otolith organs
what are the 2 otolith organs
utricle and saccule
what does the vestibular system help with
balance, equilibrium, posture, eye movements
semicircle canals function
head rotation/ angular acceleration
otolith organs function
detect linear acceleration and change in head angle (tilt)
how many semicircle canals are there
3
what is the sensory apparatus in the otolith organs
macula
otolith organ mechanism
when head moves, gravity pulls on otoliths (calcium crystals) which pull on hair cells to either hyperpolarize or depolarize
how is the macula in the saccule orentiated
vertically
how is the macula in the utricle orentiated
horizontally
how to utricle and saccule detect all linear motion
they are perpendicular to each other and hair cells direction of depolarization split down the middle
utricular macula direction of depolarization arrows
into center; horizontal
saccule macula direction of depolarization arrows
away from center; up and down (vertical)
semicircle canal fluid
endolymph fluid
semicircle canal main anatomical parts
ampulla (bulge) and capula (gelatinous cap) connected to hair cells
semicircular canal mechanism
head moves, endolymph fluid moves in opposite direction, pulls on hair cells, depolarize
how long are hair cells depolarized before returning to baseline position: semicircular canal mechanism
15-30 seconds
what are the 3 canals on each side of the head
horizontal, anterior vertical and prosterial vertical canals
what are L and R horizontal canals sensitive to
rotation in horizontal plane
what are L anterior and R posterior canals sensitive to
45 degree rotation in vertical plane anteriorly to left
what are R anterior and L posterior canals sensitive to
45 degree rotation in vertical plane anteriorly to right
push pull mechanism
functionally paired canals have opposing effects; when one side is depolarized and opposite is hyperpolarized
cell bodies of vestibular nerve
scarpa’s ganglion
what causes dizziness
when head rotation stops, inertial of endolymph fluid bends cupula in semicircular canals -> capul bends in other direction -> opposite hair cells response -> vestibular nerve on each side of head change activity
where does the vestibular nerve (cranial nerve 8) send info
medial and lateral vestibular nucleus in brainstem and cerebellum
where does lateral vestibular nucleus send info
- cerebellum (movement coordination)
- limb motor neurons (maintain posture)
where does medial vestibular nucleus send info
- VP nucleus of thalamus -> vestibular cortex
- neck motor neurons (keep head up/ balance)
- extraocular (eye) motor neurons (stabilize vision)
what brain area primary processes vestibular information
parieto insular vestibular cortex (PIVC)
