Ch 15: Vestibulo-Ocular Response

Question 1

parts of the inner ear sense head rotations, which include

Answer 1

pitch, roll, and yaw

Question 2

head translations include

Answer 2

bob, heave, and surge

Question 3

the purpose of the rotational vestibular-ocular response is to

Answer 3

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

Question 4

what detects head rotation and what response does this provide

Answer 4

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

Question 5

what are head translations and gravity detected by

Answer 5

they are sensed by the otolithic organs of the inner ear

Question 6

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

Answer 6

produced by otolithic organs of the inner ear

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

Question 7

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

Answer 7

True

Question 8

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

Answer 8

the semicircular canals and the utricle and saccule

Question 9

what is the osseous labyrinth

Answer 9

of the temporal bone, it is filled with perilymph

Question 10

the membranous labyrinth of the osseous is filled with?

Answer 10

endolymph

Question 11

what are important portions of the membranous labyrinth?

Answer 11

vestibule, utricle, and saccule, semicircular canals and cochlea

Question 12

what are the 3 semicircular canals?

Answer 12

• lateral
• anterior
• posterior

Question 13

ampulla importance

Answer 13

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

Question 14

cupula importance

Answer 14

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

Question 15

cupula and ampulla are connected how

Answer 15

the cupola forms a watertight seal inside the ampulla

Question 16

how does endolymph affect this cupula

Answer 16

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

Question 17

in the cupula, input to the system is in

Answer 17

angular acceleration of the head

Question 18

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

Answer 18

angular velocity

Question 19

excitatory and inhibitory for:

right lateral canal and left lateral canal

Answer 19

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

Question 20

excitatory and inhibitory for:

right anterior canal and left posterior canal

Answer 20

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

Question 21

excitatory and inhibitory for:

left anterior canal and right posterior canal

Answer 21

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

Question 22

what is caloric stimulation

Answer 22

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

Question 23

warm air in right ear would cause

Answer 23

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)

Question 24

cold air in the right ear would cause

Answer 24

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)

Question 25

how can COWS mnemonic help you remember caloric stimulation

Answer 25

Cold-Other-Warm-Same - cold in one ear causes saccade to other side - warm in one ear causes saccade to same side

Question 26

describe the maculae of the utricle and saccule

Answer 26

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

Question 27

what are otoliths and how do they affect hair cells?

Answer 27

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

Question 28

what do the maculae transduce

Answer 28

the maculae transduce linear acceleration of the head and gravitational force

Question 29

where are hair cell sensory receptors found?

Answer 29

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

Question 30

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

Answer 30

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

Question 31

hair cells only respond to forces applied along their:

Answer 31

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

Question 32

what is the rotational vestibulo-ocular response (rVOR)

Answer 32

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

Question 33

rVOR slow phase is

Answer 33

opposite direction to head rotation

Question 34

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

Answer 34

the same direction as head motion

Question 35

in rVOR, the slow and quick phases comprise the

Answer 35

vestibulo-ocular nystagmus

Question 36

when is the rotational VOR best?

Answer 36

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

Question 37

what type of frequencies does rVOR respond best to?

Answer 37

high temporal frequencies | high pass system

Question 38

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

Answer 38

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

Question 39

what is post rotatory nystagmus

Answer 39

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

Question 40

example of post rotatory nystagmus and how

Answer 40

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

Question 41

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)

Answer 41

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)

Question 42

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

Answer 42

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

Question 43

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

Answer 43

prentice's rule

Question 44

prentice's rule

Answer 44

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

Question 45

voluntary changes in gaze are usually accomplished by a combination of

Answer 45

head saccade and eye saccade

Question 46

head saccade and eye saccade working together causes

Answer 46

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

Question 47

difference between what optokinetic and VOR respond best to

Answer 47

optokinetic- slow, sustained optic flow | vestibulo-ocular- fast, brief head rotations

Question 48

what is translational vestibulo-ocular response and is it important

Answer 48

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

Question 49

what does the parallel swing experiment show?

Answer 49

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

Question 50

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

Answer 50

Sherrington's law

Question 51

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

Answer 51

Hering's law

Question 52

what does the flocculus of the cerebellum do?

Answer 52

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