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Flashcards in Visual System Deck (67)
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1

horizontal gaze (right) steps

L cortex FEF activated
R pontine gaze center @ paramedian pontine reticular formation (PPRF)
R abducens nuc (synapse on 2 things)
1. abducens (VI) contract R lateral rectus muscle
2a. cross midline, along medial longitudinal fasciculus to oculomotor nuc in midbrain
2b. occulomotor (III) contract L medial rectus muscle

2

lesion to abducens nerve

stop ipsilateral abduction
(R lesion, R eye can't abduct)

3

lesion to abducens nucleus

bilateral inability to look towards lesion (abduct ipsi, adduct contra)

4

lesion to PPRF

bilateral inability to look towards lesion (abduct ipsi, adduct contra)

5

abducens nuc lesion complications

may have ipsi facial paralysis (VII loops around nuc)

6

lesion MLF

internuclear opthalmoplegia
contra eye cannot adduct (for conjugate)
convergence in tact (EdWest still ok)
ipsi eye has nystagmus

7

differentiate MLF vs III lesion

cannot adduct but can elevate --> III in tact
convergence is intact --> III in tact

8

lesion cerebral cortex (primary visual - FEF)

neither can look to contra side (R lesion, can't look L)
slow drift to ipsi side (R lesion, drift R)

9

complications of primary visual cortex lesion

FEF close to RUL motor cortex
may have RUL weakness

10

aqueous humor path

secreted by ciliary bodies into post chamber
go thru pupil
circulate in ant chamber
taken up by canal of schlemm
go to venous system

11

glaucoma mech

problem draining aqueous humor --> intraoccular P builds up --> optic disc cupping - affect longest nerves first (lose peripheral vision)

12

light reflex (constriction) steps

1. light stim optic nerve
2. optic n stim pretectum (in midbrain)
3. stim both EdWest nucs
4. both pregang para III synapse in ciliary ganglia
5. both postgang para stim pupillary constrictor muscle
6. pupil constricts (miosis)

13

neurosyphilis and light reflex

affect pretectum
stop pupillary light reflex bilaterally
near response in tact
(Argyll Robertson pupil)

14

pineal tumor and light reflex

compress pretectum
stop pupillary light reflex bilaterally
near response in tact
(Argyll Robertson pupil)

15

light reflex (dilation) steps

hypothalamus
DHF
T1
superior cervical gang
pupillary dilator muscle

16

events of near response

accommodation
convergence
pupillary constriction

17

accommodation steps (in near response)

para fibers contract ciliary muscle (relax suspensory ligs - become rounder)

18

ciliary muscle actions

contract: relax suspensory ligs - lens becomes rounder - see things close

relax: contract suspensory ligs -lens become flatter - see things far

19

convergence (in near response)

III innervates both medial rectus muscles --> adduct both

20

near response steps

stim visual cortex
superior colliculus and pretectal nuc
EdWest
oculomotor nuc (+ ciliary gang)
III adducts both (medial rectus) (+ para constricts pupils, contract ciliary muscles)

21

Argyll Robertson pupil causes

neurosyphilis
pineal tumor
diabetes

22

Argyll Robertson pupil Sx

no direct or consensual light response
near response in tact

23

Argyll Robertson mech

lesion/compress pretectum
more neurons devoted to near than light response

24

Argyll Robertson AKA

pupillary light-near dissociation
prostitute's pupil

25

Marcus Gunn pupil AKA

relative afferent

26

Marcus Gunn mech

optic nerve lesion

27

Marcus Gunn causes

MS

28

Marcus Gunn Sx

light in affected pupil - pupils dont constrict fully
light in unaffected - pupils constrict fully
light in affected again - pupils dilate (weaker stim in II)

29

Transtentorial (uncal) herniation cause

increased intracranial pressure

30

Transtentorial (uncal) herniation mech

increased intracranial P --> uncal herniation --> CN III compressed --> affect para, add/elevate muslces, LPS