Eyelids

Question 1

3 muscles used in eyelid elevation

Answer 1

• levator palpebrae superioris
• muller’s muscle
• frontalis muscle

Question 2

innervation of elevator palpebral superioris

Answer 2

CN III

Question 3

innervation of Muller’s muscle

Answer 3

sympathetic innervation

Question 4

innervation of frontalis muscle

Answer 4

CN VII

Question 5

muscle for eyelid closing

Answer 5

orbicularis oculi (1 muscle with several divisions)

Question 6

innervation of orbicuaris oculi muscle

Answer 6

CN VII

Question 7

importance of the palpebral portion of orbicularis oculi

Answer 7

palpebral portion within eyelid itself and has muscle of Riolan at lid margin with fine muscle fibers

Question 8

2 main functions of muscle of Riolan

Answer 8

1. keep lid margin pressed against globe

2. keep openings of meibomian glands closed except when oil needs to be released

Question 9

how is the orbital portion of the orbicularis oculi distringuished from the palpebral portion?

Answer 9

based on excitability: palpebral portion has lower threshold for excitation

Question 10

muscle and its innervation used for frowning

Answer 10

corrugator supercilii, CN VII

Question 11

describe Herings law of equal innervation

Answer 11

same muscle on 2 sides of the body receive same amount of neural stimulation (ex: levator L/R, lids L/R fischer width)

Question 12

describe Sherringtons law of reciprocal innervation

Answer 12

two antagonistic muscles (ex: levator and ocularis) when one is stimulated, other is inhibited

Question 13

what are the 3 reflex blink afferent pathways?

Answer 13

• trigeminal (CN V): corneal, facial
• optic (CN II): dazzle, glare, menance
• auditory (CN VIII): auditory

Question 14

what reflex is the last reflex lost under general anesthesia?

Answer 14

corneal reflex

Question 15

corneal reflex is the first reflex lost in:

Answer 15

cerebellar pontine angle tumor

Question 16

what is the reflex latency for corneal reflex?

Answer 16

about 160 ms

Question 17

what reflex can be an early sign of Parkinson’s disease and why?

Answer 17

facial reflex, because normal patients can withhold this reflex and patients with parkinson’s can not (called Myerson’s sign)

Question 18

what is unique about the dazzle reflex pathway?

Answer 18

remains in decorticate animals (without V1) so it is also a subcortical pathway

Question 19

normal blink rate is every:

Answer 19

12-15 times/ minutes or 4-5/sec

Question 20

blinking can be affected by:

Answer 20

• excitation level
• ocular irritation
• concentration level

Question 21

describe the dynamics of eyelid motion

Answer 21

lids close like a zipper, starts lateral and closes in a medial direction

Question 22

blink suppression can especially suppress what time of spatial info and using what pathway?

Answer 22

low frequency spatial info through magnocellular pathway