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Eye Movements > Ch 15: Vestibulo-Ocular Response > Flashcards

Ch 15: Vestibulo-Ocular Response Flashcards

1
Q

parts of the inner ear sense head rotations, which include

A

pitch, roll, and yaw

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2
Q

head translations include

A

bob, heave, and surge

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3
Q

the purpose of the rotational vestibular-ocular response is to

A

keep the whole visual world imaged stationary on the retina as best as possible

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4
Q

what detects head rotation and what response does this provide

A

semicircular canals of the inner ear can provide a sense of head rotation- they provide the rotational vestibule-ocular response

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5
Q

what are head translations and gravity detected by

A

they are sensed by the otolithic organs of the inner ear

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6
Q

translational vestibule-ocular response caused by? is it important?

A

produced by otolithic organs of the inner ear

-it isn’t important in humans, but well developed in some animals

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7
Q

T/F: the vestibulo- ocular eye movements are primarily non-visual

A

True

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8
Q

the labyrinth of the inner ear contains two sensory systems important to eye movement and posture. these are

A

the semicircular canals and the utricle and saccule

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9
Q

what is the osseous labyrinth

A

of the temporal bone, it is filled with perilymph

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10
Q

the membranous labyrinth of the osseous is filled with?

A

endolymph

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11
Q

what are important portions of the membranous labyrinth?

A

vestibule, utricle, and saccule, semicircular canals and cochlea

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12
Q

what are the 3 semicircular canals?

A
  • lateral
  • anterior
  • posterior
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13
Q

ampulla importance

A

it is a dilated portion of the canal which contains the crust ampullaris, a ridge covered in sensory hair cells

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14
Q

cupula importance

A

it is a tall, cone-shaped flap of gelatinous glycoprotein attached to the crust ampullaris, it surrounds the sterocilia and kinocilia of the hair cells

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15
Q

cupula and ampulla are connected how

A

the cupola forms a watertight seal inside the ampulla

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16
Q

how does endolymph affect this cupula

A

endolymph can deviate and bend the cupula, and thus act on the hair cells
-the cupula has a viscous drag that opposes the force of the endolymph

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17
Q

in the cupula, input to the system is in

A

angular acceleration of the head

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18
Q

what is the output of the hair cells in the cupula in

A

angular velocity

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19
Q

excitatory and inhibitory for:

right lateral canal and left lateral canal

A

-right yaw excites right lateral canal and inhibits left lateral canal

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20
Q

excitatory and inhibitory for:

right anterior canal and left posterior canal

A

-downward head pitch combined with right head roll excited right anterior canal and inhibits left posterior canal

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21
Q

excitatory and inhibitory for:

left anterior canal and right posterior canal

A

-downward head pitch combined with leftward head roll excites the left anterior canal and inhibits the right posterior canal

22
Q

what is caloric stimulation

A

is an artificial alternative to head rotation for producing a vestibulo-ocular response. it relies on section currents in endolymph produced by warm or cold applied to one ear canal

23
Q

warm air in right ear would cause

A

upward vection currents that stimulate a rightward head motion, which is excitatory for the right lateral canal
(with compensatory slow-phase eye movement to the left and fast saccade to the right)

24
Q

cold air in the right ear would cause

A

downward section currents that stimulate a leftward head motion, which is inhibitory for the right lateral canal (with compensatory slow-phase eye movements to the right and fast saccade eye movement to the left)

25
Q

how can COWS mnemonic help you remember caloric stimulation

A

Cold-Other-Warm-Same

  • cold in one ear causes saccade to other side
  • warm in one ear causes saccade to same side
26
Q

describe the maculae of the utricle and saccule

A

the maculae are located roughly in perpendicular planes, both planes are actually curved

27
Q

what are otoliths and how do they affect hair cells?

A

otoliths are calcium carbonate crystals, they are denser than endolymph and lag behind when force is applied, so they bend the hairs of the hair cells

28
Q

what do the maculae transduce

A

the maculae transduce linear acceleration of the head and gravitational force

29
Q

where are hair cell sensory receptors found?

A

in the crust ampullaris of the semicircular canal, the macula utriculi in the utricle, and the macula sacculi in the saccule

30
Q

what does it mean when cells have a ‘tonic’ firing rate?

A

they are excited by force in one direction and inhibited by force in the other

31
Q

hair cells only respond to forces applied along their:

A

plane of polarization (hair cells all have the same plane of polarization), which corresponds to the plane of the semicircular canal

32
Q

what is the rotational vestibulo-ocular response (rVOR)

A

the response stimulated by the semicircular canal receptors, primarily non-visual

33
Q

rVOR slow phase is

A

opposite direction to head rotation

34
Q

in rVOR, slow phases are interspersed with quick phases (saccades) in

A

the same direction as head motion

35
Q

in rVOR, the slow and quick phases comprise the

A

vestibulo-ocular nystagmus

36
Q

when is the rotational VOR best?

A

best to brief head rotations
-it is not so good for responding to sustained rotation of the head
(shortest of any eye movement class)

37
Q

what type of frequencies does rVOR respond best to?

A

high temporal frequencies

high pass system

38
Q

in near vision (convergence), how is the VOR response different any why?

A

in near vision, the eyes must counter-rotate relatively more for the same head rotation
(gain in VOR increases during convergence of the eyes)

39
Q

what is post rotatory nystagmus

A

it is observed when angular velocity changes after a long period of rotation at a constant angular velocity

40
Q

example of post rotatory nystagmus and how

A

spinning in barony chair and then abrupt halt, this stilettos acceleration in the direction opposite to the original constant-velocity motion

41
Q

explain the results of post-rotatory nystagmus when spinning a person clockwise at constant angular velocity just after you bring them to a halt
(and what eye movements result-slow/fast)

A

after halt, the head is stationary but the endolymph has inertia to continue in a clock-wise path
-this places force on cupula that simulate a counter-clockwise rotation from a standing start
(slow phase to Right, fast phase to Left)

42
Q

what does it mean by vestibulo-ocular system is feed-forward?

A

its accuracy depends on adapting the feed-forward gain to optimize the response

43
Q

the prismatic effects of spectacle lens varies in off-gaze by

A

prentice’s rule

44
Q

prentice’s rule

A

p = c F
p=prismatic effect in prism diopters
c= distance from optical center in cm
F= lens power in diopters D

45
Q

voluntary changes in gaze are usually accomplished by a combination of

A

head saccade and eye saccade

46
Q

head saccade and eye saccade working together causes

A

head saccade produces a slow phase VOR opposite to eye saccade direction

47
Q

difference between what optokinetic and VOR respond best to

A

optokinetic- slow, sustained optic flow

vestibulo-ocular- fast, brief head rotations

48
Q

what is translational vestibulo-ocular response and is it important

A

they are non-visual, function is to maintain stable gaze for the whole visual environment despite linear acceleration, not too important in humans

49
Q

what does the parallel swing experiment show?

A

used to demonstrate small pitch eye movements during linear for-aft acceleration

50
Q

the arrangement of excitatory and inhibitory pathways to a single eye is an example of ‘wiring’ for :

A

Sherrington’s law

51
Q

the arrangement of signals to yoke muscles in the two eyes is an example of wiring; for:

A

Hering’s law

52
Q

what does the flocculus of the cerebellum do?

A

it is involved in VOR plasticity by integrating information and making the response more accurate
(long term visual calibration mechanism)

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