Lecture 16- Movement of extraocular muscles

Question 1

horizontal movement of the eyes mediated by which movement and muscles

Answer 1

• ABDUCTION- lateral rectus muscle
• ADDUCTION- medial rectus muscle

Question 2

abduction mediated by

Answer 2

lateral rectus muscle

Question 3

adduction mediated by

Answer 3

medial rectus muscle

Question 4

outline which movement and which muscles are involved in horizontal movemnt of the eyes to the left

Answer 4

• Right eye – ADDUCTION
  
  • medial rectus muscle
• Left eye- ABDUCTION
  
  • lateral rectus muscle

Question 6

outline which movement and which muscles are involved in horizontal movemnt of the eyes to the right

Question 7

action of superior rectus

Answer 7

• Elevates eyeball but has some additional actions

Question 8

Superior and inferior rectus arise from

Answer 8

the apex of the orbit

Question 9

SR inserts

Answer 9

obliquely into superior anterolateral surface of the flobe

Question 10

action of superior rectus muscle if starting from primary resting gaze

Answer 10

• elevate
• slightly adducts (plls eyes medially)
• slightly intorts (internall rotates)

Question 11

Superior rectus muscle is a more powerful elevator when

Answer 11

eye is positioned laterally

Question 12

action of inferior rectus muscle

Answer 12

• Depresses eyeball but no additional actions
• Opposite to superior rectus muscle

Question 13

IR inserts obliquely into

Answer 13

anteroinfeiror surface of the globe

Question 14

action of IR

Answer 14

• depress
• slightly adducts (pulls eye medially)
• slightly extorts (externally rotates)

Question 15

IR is a more powerful depressor when

Answer 15

eye is posititoned laterally

Question 16

both SR and IR are more powerful in their action when

Answer 16

positioned laterally

Question 17

action of superior oblique

Answer 17

• Intorts the eyeball but also depresses
• Trochlear functional origin

Question 18

SO muscle arises from

Answer 18

apex of orbit, passes throguh trochlea, inserts into superior- posterior aspect of the globe (posteruor to equator)

Question 19

SO action (if starting from primary resting gaze)

Answer 19

• intorts internally
• depresses
• slighlty abducts (pulls eye laterally)

Question 20

SO is most powerful as a depressor when

Answer 20

eye is posittioned medially

Question 21

Inferior oblique action

Answer 21

• Extort eyeball but also elevates
• Mirror image of SOM
• From floor of orbital cavity

Question 22

IO arises from

Answer 22

anteromedials urface of floor of orbit

inserts into infero-posteiror aspect of globe (posteiror to equator)

Question 23

action of IO from primary resting gaze

Answer 23

• extort -externally rotate
• elevate
• slightly abduct (pulls eye laterally)

Question 24

IO most powerful as an elevator when

Answer 24

eye is positioned medially

Question 25

IO and SO most powerful when

Answer 25

positioned medially

Question 26

which extra-ocular msucle shave an action in elevating the eye ball?

Answer 26

superior rectus and infeiror oblique

Question 27

which extra-ocular muscles have action in depressing the eye ball

Answer 27

inferior rectus and superior oblique

Question 28

which extra-oclar muscles are stornger elevators and depressors of the eyeball when the eye is in the adducted posittion

Answer 28

Elevator: inferior oblique, depressor: superior oblique

Question 29

which extra-oclar muscles are stornger elevators and depressors of the eyeball when the eye is in the abducted posittion

Answer 29

elevator: superior rectus, depressor: inferior rectus

Question 30

if a muscle(s) is weakened

Answer 30

its infleunce (i.e. exerted by its anatomical action on the eyeball) is lost (or reduced) - other muscle actions no longer antagonised (balanced out) - difficulty with moving eye in certain directions of gaze

Question 31

resting position pf eye when a muscle is weakened

Question 32

weakness of eye may only be apaprent

Answer 32

on clinical exam

Question 33

1. In what pisition is the abnormal eye held

Answer 33

**1. ADDUCTED- medially**

Question 34

what muscular action on the eyeball is no longer acting on the eye, given its position

Answer 34

action that pulls eye medially unopposed- ABDUCTION - lateral rectus

Question 35

which nerve innervates the lateral rectus

Answer 35

abduences (CN 6)

Question 36

2. in what position is the abnormal eye held?

Answer 36

## Footnote **1. Elevated and ADDUCTED (medial)**

Question 37

what muscular action on the eyeball is no longer action on the eye given its position

Answer 37

depression and abducted (down and out) - superior oblique

Question 38

which nerve inverbates the superior oblique?

Answer 38

CN IV- trochlear