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64 Cards in this Set

  • Front
  • Back
2 Major Components of the Vestibular System
1. Semicircular Canals (SCC)
2. Otolymph System
-Utricle and Sacculus
how many SCC are there?
3 on each side
horizontal(lateral)
superior/anterior
Posterior
Angular Acceleration

Linear Acceleration
when your head moves on your neck in relation to body
like driving away from stoplight in sports car
SCC sense what type of acceleration?

Otoliths?
angular acceleration


linear acceleration
Yaw

Pitch

Roll
turning head on vert axis. like saying 'NO'
nodding head 'yes'

laterally bending head
Vestibulo-occular reflex
compensatory eye mvmt in response to head movement

rapid, 8-10ms
Vestibulo-colic reflex
maintain neck posture in relationship to body, despite head moving
Vestibulo-spinal reflex
maintain our posture if we start to fall over
rapid reflexes
difference b/w hair cells in vestibular system vs auditory system?
no Outer Hair Cells
Tip Links
link stereocilia together and then link to Kinocilium
Kinocilium are linked to
mechanoreceptors
tied to channels that allow K influx
when stereocilia move towards kinocilium

when stereocilia move away from kinocilium
cause stretch and k influx, depolarizes cell, inc NT rel

tiplinks under less tension, K flow stops, hyperpolarizes, less NT rel, reduce aff firing
2 structures detect linear accelerations
1. sacculus
2. utricle
utricle is oriented

sacculus is oriented

both of those are...
linearly

offset vertically

orthogonal to eachother
utricle hair cells partitioned

sacculus hair cells partitioned
pointing towards midline

away from midline
Linear acceleration works by
whether the stereocilia/kinocilium are deflected towards or away from eachother
-result in depol or hyperpol
Otoconia
calcium carbonate crystals
3-30microns
sit atop gelatinous otolythic membrane that surround stereocilia and kinocilium of HC
2 things can activate the HC system
1. static tilt- tilt head and hold. gravity pulls otoconia to ground
2. Rapid acceleration w/o head tilt- cause hairs to bend
do the utricles behave dfft in tilting vs linear accel?
NO. they behave the same
how does the body tell the difference b/w tilting and accel?
how long the stimulus lasts

Accel- short, transient stim
Tilting- sustained effect
Push-Pull Fashion
discharge rate goes up when tilted in one direction
goes down when tilted in another direction
T/F: one hair cell can give info about tilts in both direction.
True
Angular acceleration rotates the head in 3 fasions
1. yaw
2. pitch
3. roll
Ampulla
swelling at the base of all SCC
Cupula
in the SCC, stereocilia are projected up into this sail-like membrane
spreads across the inside of the ampulla
orientation of hair cells in the SCC

in the sacculus and utricle?
in the SAME direction


opposite directions
movement to the left does what to the cupula?


what happens to cilia/kinocilium
displaces it in opp direction due to the movement of endolymph by inertia

if the stereocilia move towards kinocilium, you get depolarization
-away=hyperpolariz
The Left and Right Horizontal Canals are oriented how?
30deg upward of the horizontal plane
how do you bring the horizontal canals into a true horizontal plane?
tilting your head down 30degrees
How do horizontal canals work together to achieve VOR?
work in parallel
push-pull fashion
RALP


LARP
rt ant and lft post work in parallel plane
-pt 45deg to rt
lft ant and rt post work in parallel plane
-pt 45deg to left
with in the pairs, moving in a direction will result in what?
increase firing from one and
decrease firing in the other

each part of pair oriented in same plane BUT in OPP directions
How are the Ant and Post canals situated?
90deg away from each other
Plane of Sacculus and Utricle is what?
90deg away from each other

utricle is 30deg up from true horizontal.
sacculus is 60 deg down from true horizontal
when does the Sacculus have maximum sens to vertical linear acceleration?
when the head is tilted down 30degrees
when does the Utricle have maximum sens to horizontal linear acceleration?
when the head is tilted down 30 degrees
orientation of hair cells in rt ampulla vs lft ampulla
are DIFFERENT
will cause opposite responses
-hyperpolariz or depolariz
if you turn your head left, which way does the endolymph fluid move?

what happens?
to the right and exerts pressure on the Cupula


lft SCC HC depolarize- inc Aff
rt SCC HC hyperpol- dec Aff
SCC are sensitive to

Firing rate of Aff fiber relates to

why?
acceleration

head velocity

b/c of viscosity of endolymph fluid
over all, signals from the vestibular system tell
how fast the head is moving in one direction
VOR generates commands that
generate eye velocity in the opp direction
eye movement signals come into?

where is this?
Medial Vestibular Nucleus

rostral medulla
where does the MVN relay fibers to?

where is this?

what does this control?
the Abducens nucleus

in the pons

the lateral rectus muscles
rotate head to left inc firing..
stimulates what?

inhibits what?
of the left SCC
stimulates Rt Lateral Rectus

inhibits Lft Lateral Rectus
excitory stimuli from the abducens nucleus goes to what?

inhibitory stimuli?
the contralateral lateral rectus


to the ipsilateral lateral rectus
in aff signals from Left SCC causes...
1. inc left MVN
2. lft mvn->excit rt abducens nucleus
3. this stimulates rt lateral rectus
4. lft mvn-> inhib lft abducens nucleus
5. this inhibits lft lat rectus
Medial recuts control

lft abducens nuclei

Rt abducens nuclei
via the MLF pathway

stim lft occulomotor nuc->stim lft medial rectus
inhib rt occulomotor nuc->inhib rt medial rectus
Vestibular system is best tuned to what frequencies?
HIGH freq

compensate better at high freq
w/ slow mvmt, there is not much endolymph mvmt, not many signals
Vestibular projections into the SC are impt for what?

run in?
balance control
from lat and med vestib nuclei

lateral vestibulospinal tract ipsilaterally
the VST that cross run in?

to form?

control what?
MLF

Medial VST

axial musculature
what gives primary input to the Lateral Vestibulospinal Tract
primarily Otolith organ input
what is lat VST involved in?
powerful extensor muscle mvmt and maintaining posture

deflects body tilting w/ extensors
where does the Medial VST come from?

involved in?
which reflex is involved?
MLF


modulates head postion, neck muscles
vestibulo-colic, brings next/body into position even with head tilted
where do cortical projections of vestibular nuclei arise from?
lateral and superior vestibular nuclei in the pons
how are the vestibulo-cortical projections relayed?
through the Ventroposterior nucleus of the Thalmus
which 3 areas of the cortex are the vestibulo impulses relayed to?
1. Face representation in SSI
-determines if you are moving towards something, or if its moving to you
2. Area 3a
3. Post Parietal Cortex
-eye pos signals and neck aff signals
which SCC and which otolith are both angled 30deg above midline?
horizontal SCC and Utricle
where does the lateral vestibulospinal tract terminate?
in the ventral horn
lateral vestibular nuclei is in

medial vestibular nuclei is in
the mid pons

the rostral medulla
what generates the lat VST? where does it end?
otoliths, mid pons
ipsilaterally to the ventral horns, extensor muscles
what generates the med VST?

where does it terminate?
SCC, rostral medulla
goes via MLF bilaterally
cervical medial ventral horns

controls head position/neck muscles
where do the cortical projections from the vestibular system arise?
lateral and superior vestibular nuclei in the pons
what are the cortical projections relayed in?
Ventroposterior nuc of thalmus
VP of thalmus projects to what 3 areas?
1. face representation of SSI
2. Brodman's Area 3a
3. Post Parietal Cortex

all of these integrate body orientation in space