Ocular: EOMs

Question 1

What is the difference between skeletal muscle and the EOMs

Answer 1

EOMs are skeletal muscles but they differ by:
-denser blood supply
-their connective tissue sheets contain more elastic fibers
-have fewer muscle fibers per motor unit, which enables fine motor control and accurate movement

Question 2

Fine motor control and accurate movements in EOMs comes from

Answer 2

EOMs having fewer muscle fibers in a motor unit

Question 3

What is the sarcolemma?

Answer 3

Muscle cell membrane

Question 4

What are t tubules?

Answer 4

-invagination of sarcolemma in muscle
-Allow for ions to spread throughout the cell when stimulated by an action potential

Question 5

What is the sarcoplasm?

Answer 5

Muscle cell cytoplasm

Question 6

What are myofibrils?

Answer 6

Typical cellular structures contained by sarcoplasm

Question 7

What are the differences between actin and myosin?

Answer 7

Actin:
-thin

Myosin:
-thick

Question 8

What is a sarcomere?

Answer 8

-thick and thin filaments are organized into bands that repeat along length of the myofibrils in sections called sarcomere

Question 9

What are the two bands in a sarcomere?

Answer 9

I band
A band

Question 10

I band:

Answer 10

-isotropic
-contains two sets of actin filaments connected to each other at the z line

Question 11

A band:

Answer 11

-anisotropic
-contains both actin and myosin filaments

Question 12

How is the I band affected during contraction?

Question 13

How is the A band affected during contraction?

Question 14

What is the H zone and how is it affected by contraction?

Answer 14

-contains only myosin filaments
-shortens with contraction
-which in turn shortens the length of the entire muscle when contracted

Question 15

What is the Z line?

Answer 15

Dark vertical line that delineates one sarcomere from the next

Question 16

Superior rectus primary, secondary, and tertiary actions:

Answer 16

1. Elevation
   2.intorsion
   3.adduction

Question 17

Superior oblique primary, secondary, and tertiary actions:

Answer 17

1.intorsion
2.depression
3.abduction

Question 18

Lateral rectus primary, secondary, and tertiary actions:

Answer 18

Trick!
Abduction only

Question 19

Inferior rectus primary, secondary, and tertiary actions:

Answer 19

1. Depression
   2.extorsion
   3.adduction

Question 20

inferior oblique primary, secondary, and tertiary actions:

Answer 20

1. Extorsion
2. Elevation
3. Abduction

Question 21

Medial rectus primary, secondary, and tertiary actions:

Answer 21

Dur
Adduction

Question 22

Innervation of the EOMs

Answer 22

LR6 SO4 3

Question 23

What is Herring’s law of Equal innervation?

Answer 23

The concept of equal innervation of yoked muscles
-The muscle act simultaneously and have equal innervation so that each yoked muscle receives the same amount of stimulation

Question 24

What are yoked muscle?

Answer 24

Are two muscles that act together to allow for concerted movement of the globes
Example: in right gaze the right lateral recuts and left medial recuts work in concert

Question 25

What is Sherrington’s law of reciprocal innervation?

Answer 25

contraction of EOMs must be accompanied by simultaneous and equal relaxation of its antagonists in order to have smooth, concerted movement of both eyes

Question 26

What is duction?

Answer 26

Movement of only one eye
-occurs around the axis of fick

Question 27

What are the six duction movements

Answer 27

Abduction and adduction(vertical axis,Z)
Supraduction and infraduction( horizontal axis, X)
Intorsion and extorsion (saggittal, Y)

Question 28

What is vergence?

Answer 28

Movement of both eyes in opposite left-right directions (disconjunctive movement)

Question 29

Two types of vergence

Answer 29

Convergence and divergence

Question 30

What is version?

Answer 30

Movement of both eyes in the same direction (conjunctive movement)