Vestibular Ocular Reflex (M2) Flashcards Preview

III. Binocular Vision > Vestibular Ocular Reflex (M2) > Flashcards

Flashcards in Vestibular Ocular Reflex (M2) Deck (32):
1

What is the test of vestibular function in which you produce a vestibular nystagmus using heat convection called? 1. What can this tell you? 2

1. caloric stimulation
2. determine if canal is hyper or hypo

2

What is the disease of the vestibular system that is a change in the viscosity of the endolymph (hyper or hypo)?

Meniere's disease

3

What is the timing of Benign paroxysmal positional vertigo? 1. Which canal is most commonly affected? 2

1. sudden attack
2. posterior vertical

4

What is another term for linear acceleration? 1. What measured this? 2

1. translational acceleration
2. otolith

5

If the left horizontal canal is constantly suppressed (hypo-stimulation) what would be the associated eye movements?

right beating nystagmus

6

What is the region of epithelium of both the utricle and saccule that contains a dense aggregate of hair cells that sense forces?

macula

7

What are the reasons for dizziness/oscillopsia when there is vestibular illness?

1. mismatch between proprioception and VOR signals
2. mismatch between what you see and what your proprioception is telling you

8

When the head translates (linearly accelerates) what happens to the otolithic membrane?

membrane slides and pulls on cilia, causing an increase or decrease in firing rate

9

What happens to the phase and gain at lower frequencies of rotation (less than 0.01 cyc/sec)?

phase difference increases and gain falls

10

What type of movements does the saccule best respond to?

up and down translations of the head

11

What is the vertically oriented part of the otolith? 1. What does it respond to? 2

1. saccule
2. vertical translational acceleration

12

What type of movements does the utricle best respond to?

1. sustained lateral tilts (head to shoulder)
2. sustained fore-aft tilts (pitch forward or backward)
3. side to side translations of the head

13

What is the latency of translational VOR (TVOR)?

35ms

14

What is the antibiotic that can knock out the RVOR and leads to the person not being able to recognize faces or read street signs without standing still?

streptomycin

15

Does the likeliness of nystagmus increase or decreases if the head is moved in the orientation of the canal for Meniere's disease?

increase

16

What are the plots that represent the relationship between gain and frequency along with phase and frequency?

Bode plot

17

What gives a response similar to the VOR but is initiated by stretch receptors in the neck rather than vestibular apparatus? 1. When is this important? 2

1. cervico-ocular reflex
2. subjects who have lost normal vestibular function

18

What are the signs and symptoms of vestibular illness?

1. vestibular nystagmus (worse when in direction of canal affected)
2. dizziness/oscillopsia
3. can't see while walking

19

How are the kinocilium arranged in the otolith?

variable (different hair cells respond to forces in different directions)

20

What is test of VOR function that measures how the eye velocity (output) corresponds to the head velocity (input)? 1. How is it usually measured? 2. What is perfect score? 3

1. gain (ratio of output velocity/input velocity)
2. sinusoidal stimulation (rotate head back and forth)
3. 1.00

21

What is caused by calcium carbonate crystals breaking free from the utricle and entering one of the canals? 1. What are the crystals called? 2

1. Benign paroxysmal positional vertigo (BPPV)
2. otoconia

22

Where do the cilia of the macula in the utricle and saccule extend into? 1. What is contained there? 2

1. otolithic membrane
2. crystals of calcium carbonate

23

Does vestibular neuritis cause hyper or hypo stimulation? 1. What are the possible causes of this? 2. Does the nystagmus increase or decrease when you turn your head in the direction of the affected canal? 3

1. hypo
2. viral infection, stroke, tumor, aneurysm, ischemia, MS
3. increase or may increase in any direction if all canal affected

24

What is the common etiology of Benign paroxysmal positional vertigo for a person under age 50? 1. Over 50? 2

1. head injury
2. idiopathic

25

What is a free floating otoconia called that leads to Benign paroxysmal positional vertigo? 1. An otoconia stuck to the cupula? 2

1. canalithiasis
2. cupulothiasis

26

What is the horizontally oriented part of the otolith? 1. What does it respond to? 2

1. utricle
2. horizontal translational acceleration and shift in gravity vector due to tilt

27

What is test of VOR function that measures the difference in position between eye and head? 1. What is a perfect score? 2

1. phase
2. 180deg out of phase

28

What is the procedure for caloric stimulation?

1. tilt head back 60deg so lateral canal vertical
2. apply hot water (or cold to right ear) to the left ear
3. induces leftward beating nystagmus (COWS= cold opposite, warm same)

29

What is the eye movement that refers to the cycloversion that accompanies tilt of the head? 1. What is the organ that is responsible for this? 2.

1. counter-rolling
2. otolith organ

30

Does the likeliness of nystagmus increase or decreases if the head is moved in the orientation of the canal for Benign paroxysmal positional vertigo?

increase

31

If the left horizontal canal is constantly stimulated (hyper-stimulation) what would be the associated eye movements?

jerk nystagmus with left beating as fast phase left

32

In the otolith, does bending of the stereocilia towards the kinocilium cause depolarization or hyperpolarization? 1. Is this an increase or decrease in firing rate? 2

1. depolarization
2. increase