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Neuro Test 2
Vestibular System
48
Dentistry
Professional
02/08/2014

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Term
Where is the vestibular system found?
Definition
The inner ear
Term
The vestibular organs (the part of the ear that senses motion) send their signals through the vestibular part of which cranial nerve?
Definition
CN VIII
Term
Which structures work on the right and left side to detect rotations of the head in all 3 directions (ANGULAR ACCELERATIONS)?
Definition
semicircular canals
Term
How many semicircular canals are there?
Definition
3
Term
Which structures sense LINEAR ACCELERATIONS (such ads gravity)?
Definition
otoliths
Term
What two structures make up the otolith?
Definition
sacculus and utricle
Term
The (otoliths/semicircular canals) can tell you when your body is tilted one direction or another.
Definition
otoliths
Term
moving your chin up and down (in a "yes" nodding motion) is called what?
Definition
pitch
Term
moving the ear towards the shoulder is called a what?
Definition
roll
Term
the movement of shaking your head (as if saying "no") is called what?
Definition
yaw
Term
what is the reflex in which eye velocity compensates for head velocity? (Keeping visual field stable even when you are shaking your head very quickly)
Definition
vestibulo-ocular reflex
Term
what is the reflex which allows head position to be maintained despite body movements?
Definition
vestibulo-colic reflex
Term
what is a reflex that involves postural changes in response to a vestibular signal?
Definition
vestibulospinal reflex
Term
under normal circumstances, hair cells are somewhat (polarized/depolarized) and are firing a resting action potential rate
Definition
depolarized
Term
Deflection of the stereocilia toward the kinocilium causes _____ channels in the apical portions of the stereocilia and kinocilium to open.
Definition
K (potassium)
Term
K+ flows into the stereo/kinocilia from the endolymph, depolarizing the cell membrane. This depolarization in turn causes ________ channels at the base of the hair cells to open, allowing _______ to enter the cell
Definition
voltage-gated Calcium channels

Calcium
Term
____ influx into the stereo/kinocilia causes synaptic vesicles to release neurotransmitter into synaptic clefts
Definition
Calcium
Term
which neurotransmitter is most commonly released from hair cell cilia?
Definition
glutamate
Term
increased release in glutamate causes depolarization of the membrane in the post-synaptic cell, which increases the firing rate of the vestibular (efferent/afferent) fibers
Definition
afferent
Term
sterocilia moving towards kinocilia (increases/decreases) the firing rate of the afferent fibers
Definition
increases
Term
stereocilia moving away from the kinocilia causes (increase/reduction) of calcium influx, a net (increase/reduction) in neurotransmitter release, (hypo polarization/hyperpolarization) of the post-synaptic membrane, and (increase/decrease) in the firing rate of vestibular afferent fibers
Definition
stereocilia moving away from the kinocilia causes REDUCTION of calcium influx, a net REDUCTION in neurotransmitter release, HYPERPOLARIZATION of the post-synaptic membrane, and a REDUCTION in the firing rate of vestibular afferent fibers
Term
the anterior portion of the sacculus has cells that are sensitive to movement in which directions?
Definition
forward and backwards
Term
which directions of movement does the utricle sense?
Definition
medial and lateral, posterior and anterior
Term
which directions of movement does the sacculus sense?
Definition
up and down MOSTLY, (also forwards and backwards?)
Term
moving your head to the right, the utricle of one ear will move/sense _____ and the utricle of the other ear will move/sense ______
Definition
one will move/sense medial, one will move/sense lateral
Term
what are the "little rocks" in the ear that increase the effective force on the stereocilia (they sit in a gelatinous matrix where stereocilia insert)
Definition
otoconia
Term
the swelling at the base of each semicircular canal is called what?
Definition
ampulla
Term
the structure in the ampulla that is analogous to a sail that acts to intercept fluid motion is called what?
Definition
cupula
Term
what type of acceleration is the cupula sensitive to?
Definition
angular acceleration
Term
an angular acceleration causes fluid in the semicircular canals to move in the (same/opposite) direction, which displaces the cupula
Definition
opposite
Term
what are the 3 different semicircular canals?
Definition
horizontal canal
anterior canal
posterior canal
Term
if you move your head horizontally to the right while the head is tilted down 30 degrees, which canals will increase firing rate and which canals will decrease firing rate?
Definition
moving horizontally to the right, the right horizontal canal will increase firing rate, and the left horizontal canal will decrease firing rate
Term
the right anterior canal is paired with which canal on the left side?
Definition
the left posterior canal
(RALP and LARP) - R anterior/L posterior, L anterior/R posterior
Term
What head motion excites only the horizontal canals?
Definition
tilting the head down 30 degrees and rotating the head
Term
Where do the two descending vestibular spinal tracts descend from?
Definition
one descends from the LATERAL VESTIBULAR NUCLEUS
one descends from the MEDIAL VESTIBULAR NUCLEUS
Term
the (lateral vestibular nucleus/medial vestibular nucleus) is more involved in postural musculature
Definition
lateral vestibular nucleus
Term
which tract (lateral vestibulospinal tract/medial vestibulospinal tract) is more appropriate for innervation of the trunk muscles?
Definition
medial vestibulopinal tract
Term
which tract is involved in not letting you fall over when you have your eyes closed?
Definition
lateral vestibulospinal tract
Term
which tract has a huge influence on anti-gravity muscles?
Definition
lateral vestibulospinal tract
Term
The lateral vestibulospinal tract runs into the (dorsal/ventral/lateral) horn which is appropriate for innervating which muscles?
Definition
ventral horn

distal leg muscles
Term
In addition to the descending vestibular tracts there are also projections from the vestibular nuclei to the thalamus, from which information is relayed to which two places int the cortex?
Definition
parietal and somatosensory areas of the cortex
Term
vestibular signals sent to the cortex via the thalamus can allow you to do what?
Definition
move around with your eyes closed or in a dark room
Term
CN 6 (abducens) innervates which muscle in the vestibulo-ocular reflex?
Definition
lateral rectus
Term
About 40% of the cells in the abducens nucleus are internuclear neurons that project to the (ipsilateral/contralateral) oculomotor nucleus
Definition
contralateral
Term
Turning your head with your finger held in front of you, the finger seems to stay still due to which reflex?
Definition
vestibulo-ocular reflex
Term
In the vestibule-ocular reflex, turning your head to the left will cause afferents on the (right/left) to increase firing and turn eyes to the right
Definition
left
Term
T or F
Vestibular responses are good at signaling slow changes
Definition
False

Analogy is with slow movement of a glass of water, the water does not move much
Term
what movements does the utricle sense?
Definition
movements in the the horizontal plane (forwards, backwards, left, right)
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