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Physiology > Extraocular muscles > Flashcards

Extraocular muscles Flashcards

1
Q

What is the primary action of MR?

A

Adduction

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2
Q

Primary action of SO

A

Incylcotorsion

In adduction, primary action is depression

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3
Q

Primary action of IO

A

Excyclotorsion

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4
Q

Priamry action of SR

A

Elevation

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5
Q

Primary action of IR

A

Depression

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6
Q

What is function of SO / IO in adduction

A

SO - depression in adduction
IO - elevation in adduction

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7
Q

What are yoked muscles?

A

Contract to move both eyes in the same direction

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8
Q

What are yoked muscles of looking right?

A

Right lateral rectus, left medial rectus

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9
Q

What are yoked muscles of looking left?

A

Right medial rectus, left lateral rectus

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10
Q

What are yoked muscles of looking right and up?

A

Right superior rectus
Left inferior oblique

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11
Q

What are yoked muscles of looking right and down?

A

Right inferior rectus
Left superior oblique

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12
Q

What are yoked muscles of looking left and up?

A

Left superior rectus
Right inferior oblique

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13
Q

What are yoked muscles of looking left and down?

A

Left inferior rectus
Right superior oblique

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14
Q

What is the fucntion of superior rectus?

A

Elevation (max when eye abducted 24)

Incyclotorsion (maximal on adduction or medial gaze)

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15
Q

What is the fucntion of inferior rectus

A

Depression ( max when eye abducted 24

Excyclotorsion (maximal in adduction)

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16
Q

What is the fucntion of the superior colliculus?

A

rostral midbrain
Coordinates gaze shifts involving eye and head movement

17
Q

What is the cerebellar vermis invovled in?

A

Initiation of eye movements

18
Q

What are the frontal eye fields involved in?

A

Mediate contralateral saccadic eye movements

19
Q

What is version vs vergence?

A

Version is movement of both eyes in the same direction

Vergence is movements in different direction

20
Q

What is smooth pursuit movement?

A

Designed to keep an object of interest on the fovea

Emanate from occipitoparietal region

21
Q

What is Cogan’s law?

A

Desctructive lesions in occipitoparietal region may disrupt smooth pursuit to the ipsilateral side

Asymmetrical optokinetic nystagmus results

22
Q

What are saccadic movmeents?

A

Designed to place an object of interest in the peripheral visual field on the fovea

Fastest eye movements

Controlled by frontal cortex

23
Q

What are fixation movements?

A

Move the retinal image by very small intervals and prevent the image from fading due to persistent bleaching of photoreceptor pigments

24
Q

What is TRoxler’s phenomenon

A

image fading due to persistent bleaching of photoreceptor pigments

25
Q

What is optokinetic nystagmus?

A

Biphasic movmeent that can be elicited by a striped drum revolving at 30 to 100 degrees per second

Smooth pursuit is compensatory movement followed by quicker saccadic movement

26
Q

What is Floren’s law

A

Stimulation of semicircular canal leads to nystagmus in the plane of that canal, the slow phase of which is always in a direction opposite to that causing the nystagmus

27
Q

Describe caloric testing

A

Warm water stimulates horizontal canal causing smooth eye movement to contralateral side and saccadic movement to ipsilateral side

Cold water stimulates horizontal canal causing smooth eye movement to ipsilateral side and saccadic movement to contralateral side

COWS
Cold opposite, warm same (nystagmus)

28
Q

What type of muscle fibres are EOM composed of?

A

Twitch-tonic type fibres

Twitch - fast acting with en plaque motor nerve terminals - speed of response for eye tracking and vestibuloocular reflex

Tonic - slow but fatigue resistance with en grappe motor terminals for holding gaze

29
Q

What angle isolates primary action of obliques

A

39512367

39 degrees abduction

OBLIQUES ARE ABS

SO - extorts
IO - intorts

30
Q

What angle isolates secondary action of obliques

A

51 degrees ADDUCTION

ABD FIRST ADD 2

SO - depresses
IO - elevates

31
Q

What angle isolates primary action of SR IR

A

23 degrees ABDUCTION

SR
elevates

IR depresses

32
Q

What angle isolates secondary action of SR IR

A

67 degrees ADDuction

ABD 1 ADD 2

SR intort
IR extort

33
Q

What action to superior muscles have

A

INTORT

34
Q

What action to inferior muscles have

A

EXTORT

35
Q

What are tertiary action of obliques

A

ABDuction

obliques are abs

Physiology (15 decks)

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