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BMS200 > wk 14, lec 2 > Flashcards

wk 14, lec 2 Flashcards

1
Q

bipolar cells in retina are for

A

visual info. processing

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2
Q

what is lateral inhibition and what cells help with it

A

bipolar cells

brain gets sharpened signals of contrasts in light and dark, enabling fine discrimination of edges and patterns

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3
Q

rod bipolar cells vs cone bipolar cells

which ones have on renters and which ones have off renters

which is scototopic (low light) and which is photooptic (bright light)

A

rods- scototopic and on centers

cones- photooptic and on and off centers

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4
Q

rod bipolar cells- how are on renters activated

A
  • Scotopic vision (low light) and are “on-center” cells, meaning they’re activated when light falls on center of receptive field (center brighter than surround)
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5
Q

cone bipolar cells- how are on and off centres activated

A
  • On-center: activated by light hitting center of receptive field, center brighter than surround
  • Off-center: activated when light falls on surround of receptive field, surround is brighter than center
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6
Q

center- surround organization

on vs off centre activation

A

o On-center receptive fields stimulated when center brighter than surround
o Off-center receptive fields stimulated when surround brighter than center

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7
Q

oppositional regulation in on and off centres

what is the effect

A

o On and off center cells have opposite response to same stimulus (i.e. on stimulated and off inhibited)

o Enhances contrasts and edge detection, better visual acuity for brain

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8
Q

after activation, in the dark what needs to happen to rhodopsin for cells to respond again

A

needs to be regenerated

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9
Q

what happens to opsin when not working

A

bleached

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10
Q

retinal needs to be converted into which for to regenerate rhodopsin and where

A

trans to cis retinal into the pigment layer

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11
Q

what needs to combine to be ready to respond to light again

A

cis retinal and opsin

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12
Q

rods process of adaptation is slow; what is the effect of this

A

 Rods not effective at adapting to rapid light changes
 i.e. hard to adjust to bright after dark
 go into dark room pupils dilate to let as much light as possible but photopigments that were bleached take time to regenerate

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13
Q

steps in the regeneration of rhodopsin

A
  • After activation, in the dark, rhodopsin needs to be regenerated before cells can respond again

o Trans retinal separates from opsin (GPCR)
 Opsin= bleach and inactive
 Trans-retinal travels to pigment layer, converts back to cis-retinal which travels to rod to recombine with opsin = ready to respond to light again

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14
Q

what happens when you move into sunlight quickly after being in the dark

A
  • activate photoreceptors, temporarily “blinded” by overstimulation, pupils constrict and you squint to reduce light
  • rods becomes saturated (bleached) and cant respond to light
  • cones regenerate faster than rods, so they don’t saturate and continue to respond and vision becomes mediated by cones
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15
Q

horizontal cells for

A

shapen contrast

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16
Q

amacrine cells for

A

o help detect changes in vision, i.e. movement and lights on/off

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17
Q

bipolar cells for

A

process visual signals at level of retina (i.e. different patterns of lights –> on and off center)

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18
Q

how do visual signals get to the brain

A
  • visual signals from rods and cones are transmitted by ganglion cell axons to brain via optic nerve
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19
Q

steps from photoreceptors to get to brain

A

photoreceptor to bipolar cells via graded receptor potential

bipolar cells to ganglion cells via all or none action potential

go to brain via optic nerve

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20
Q

graded and action potentials in which cells

A

graded receptor potential in photoreceptor cells

action potential in bipolar cells

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21
Q

optic nerve is formed by

A
  • formed by axons of ganglion cells
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22
Q

optic nerve exits back of eyeball to create

A

optic disc (blindspot)

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23
Q

crossing of optic nerve fibers

A
  • 50% fibers cross at optic chiasm and join contralateral fibers
    o Form optic tract
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24
Q

steps of optic nerve fibers to get to the brain

A

optic nerve fibers - 50% cross at optic chiasm and form optic tract

optic tract synapses in thalamus and leaves as optic radiations

optic radiations synapse in visual cortex (occipital lobe)

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25
Q

bilateral hemianopia

A

lose outer fields in both eyes

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26
Q

right homonymous hemianopia

A

o Lose right ½ of visual field in both eyes

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27
Q

scotoma

A

area with vision loss in an otherwise normal visual field

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28
Q

primary visual cortex for

A

register shape and colour and movement

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29
Q

secondary visual cortex

A

recognize shape and colour

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30
Q

primary somatosensory cortex

A

registers sensation

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31
Q

secondary somatosensory cortex

A

recognizes sensation

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32
Q

parieto-occipito-temporal association cortex

A

combines visual and tactile info to conclude the experience (I,e finger is burnt because touched hot stove)

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33
Q

which brain regions combined the sensations from somatosenosy cortex and the colour shape and movement from the visual cortex

A

parieto-occipito-temporal association cortex

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34
Q

what happens in the brain when there’s a visual defect in the eye

A
  • Visual cortex ignores images from eye with visual defect (i.e. myopia, eye wanders)
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35
Q

amblyopia

A

vision in affected eye is worse than would be explained by visual defect alone

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36
Q

cortical blindness is a result of a lesion in the

A

primary visual cortex

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37
Q

lesions in the secondary visual cortex (responsible for shape and colour recognition) could result in 3 things

A
  1. movement agnosia
  2. visual agnosia
  3. colour agnosia
38
Q

movement agnosia (from lesion in secondary visual cortex)

A

 Object appears in another location, movement not noted

39
Q

visual agnosia (from lesion in secondary visual cortex)

A

 Inability to identify common objects as a “whole” and copy drawings

40
Q

colour agnosia (from lesion in secondary visual cortex)

A

 Grey scale

 Cerebral achromatopsia: cannot recognize colour even though cones intact

41
Q

Cerebral achromatopsia:

A

cannot recognize colour even though cones intact

42
Q

EYE MUSCLE CHART

A

look at seperate slidedeck

43
Q

medial rectus muscle

nerve innervation and action?

A

CN III (somatic)- oculomotor

adduction of eye (look to nose)

44
Q

lateral rectus muscle

nerve innervation and action?

A

CN VI- abducens

abduction eye (look to ears)

45
Q

inferior rectus muscel

nerve innervation and action?

A

CN III (somatic)

downward eye, extorsion

46
Q

superior rectus muscle

nerve innervation and action?

A

CN III (somatic)

upward eye, intorsion

47
Q

inferior oblique muscle

nerve innervation and action?

A

CN III (somatic)

elevate and abduct eye

48
Q

superior oblique muscle

nerve innervation and action?

A

CN IV- trochlear

downward and abducted eye

49
Q

levator palpebrae superioris muscle

nerve innervation and action?

A

CN III (somatic)

elevated upper eyelid

50
Q

ciliary muscle

nerve innervation and action?

A

CN III (visceral: parasympathetic)

contraction leading to increased convexity of lens

51
Q

pupillary sphincter muscle

nerve innervation and action?

A

CN III (visceral: parasympathetic)

miosis (pupillary constriction)

52
Q

which 2 muscles are innervated by visceral parasympathetic CN III (oculomotor)

A

ciliary muscle and pupillary sphincter

53
Q

I, II, III, IV

V, VI, VII, VIII

IX, X, XI, XII

A

I= nose (olfactory)
II= eye (retina)
III and IV = midbrain

V, VI, VII, VIII= pons
V (in all 3)

IX, X, XI, XII = medulla

54
Q

2 nuclei in CN III (oculomotor)

A
  • Oculomotor motor nucleus (somatic nucleus)
  • Edinger- Westphal nucleus (EDW) (visceral motor)
55
Q
  • Oculomotor motor nucleus (somatic nucleus) in CN III for what function
A

o Motor innervation to all muscles that move eye ball except superior oblique (down and abduct) and lateral rectus (abduct)

o Motor innervation for levator palpebrae superioris (elevate upper eyelid)

56
Q

what are the 2 muscles that the DOESNT the Oculomotor motor nucleus (somatic nucleus) in CN III innervate (does all others)

A

Motor innervation to all muscles that move eye ball except superior oblique (down and abduct) and lateral rectus (abduct)

57
Q
  • Edinger- Westphal nucleus (EDW) (visceral motor) of CN III is innovated by what system
A

PNS

58
Q

2 functions and muscles in Edinger- Westphal nucleus (EDW) (visceral motor) of CN III

A
  1. pupillary sphincter (miosis- pupil constrict)
  2. ciliary muscle (accomodation- near vision)
59
Q

if the oculomotor (CN III) somatic nucleus has a problem what is the pathology

A

o External ophthalmoplegia: weakness in 1+ eye muscles
 Eye symptom: down and abducted

60
Q

External ophthalmoplegia

A

weakness in 1+ eye muscles from CN III

 Eye symptom: down and abducted

61
Q

damage to visceral (EDW) of oculomotor CN III causes what

A

 pupil dilated and non-reactive to light
 ability to focus on near objects impaired (cant accommodate)

62
Q

graded vs action potentials

A

Graded potentials via bipolar cells in response to light intensity

Action potential via ganglion cells

63
Q

macular degeneration and sparing

A
  • Macular degeneration= center of retina, so lose central vision
  • Macular sparing= central vision is preserved
64
Q

glaucoma

A

peripheral vision loss (tunnel vision)

65
Q

amblyopia aka

A

lazy eye

66
Q

fix amblyopia

A

o Fix with patching or blurring drops in stronger eye to make weaker eye work, contacts, surgery,

67
Q

if someone has right primary cortex lesion what happens to vision

A

left homonymous hemianopsia (left side visual field is blind in both eyes)

68
Q

oculomotor III damage causes

A

dilated pupil (mydriasis) and loss of accommodation

69
Q

2 reflexes mediated by CN I and III

A
  1. accomodation reflex
  2. pupillary reflex
70
Q

accomodation reflex (CN I and III)

A

o object moves closer, retinal image comes out of focus so accommodation reflex is activated to help focus on the image:

71
Q

3 parts of accomodation reflex (CN I and III)

A
  1. convergence of eyes
  2. increased convexity of lens
  3. constriction of pupil
72
Q

which muscle and part of CN III for convergence of the eyes in the accomodation reflex

A

 muscle: medial rectus
 CNIII: motor

73
Q

which muscle and part of CN III for increased convexity of lens in the accomodation reflex

A

 muscle: ciliary muscle
 CNIII: EDW

74
Q

which muscle and part of CN III for constriction of pupil in the accomodation reflex

A

 Muscle: sphincter pupillae
 CNIII: EDW

75
Q

light in 1 eye causes constriction of both pupils via what CN

A

CN III EDW

76
Q

both accomodation and pupillary reflexes use what nucleus

A

EDW nucleus from CN III

77
Q

what area of brain does pupillary reflex involve and therefore damage to this area affects pupil ability to constrict

A

o Pupillary reflex involves pretectal area of midbrain (accommodation reflex doesn’t)

 Damage to pretectal area affects pupil ability to constrict

  • Can’t constrict to bright light
  • Can still constrict to accommodate
78
Q

where is trochlear IV nucleus

A

midbrain

79
Q

what is trochlear IV innervated by

A

contralateral superior oblique

80
Q

superior oblique for which motions

A

o Action: eye down and abduct
o Additional action: intorsion

81
Q

which muscle does intorsion and which does extorsion and whats the purpose

A

superior oblique= intorsion

inferior oblique= extorsion

important for visual stability when head changes position

82
Q

SIN is acronym for

A

superior oblique, intorsion, nose

83
Q

if trochlear nucleus on right side is damaged and patient looks ahead then which eye is affected? what muscle compromised? what muscle takes over? causes extorsion of intorsion?

A

o Left eye affected
o Superior oblique muscle compromised, so inferior oblique muscle takes over
o Causes eyes to rotate to ear – extorsion

 Creates double vision- diplopia
 Patient will tilt head to left to compensate and have neck pain instead of blurry vision

84
Q

when is the abducens VI nucleus

A

in the pons

85
Q

muscle for abducens VI and function

A
  • Muscle: lateral rectus
    o Abduction
86
Q

abducen mediates the lateral gaze how?

muscles?

coordinated by?

A

o Coordinated by the reticular formation in the pons (PPRF)
o Involves lateral rectus (CN VI) and medial rectus (CN III)

87
Q

which tract connects CN III, IV, VI

A
  • Medial longitudinal fasciculus (MLF) (tract) connects CN III, CN IV and CN VI (extra-occular nuclei)
88
Q

what reflex does abducens VI mediate

A

vestibule-ocular reflex

89
Q

what is vestibule-ocular reflex

A

o Eyes remain fixed to an object even when head moves

o Movement picked up by vestibular apparatus
 Send signals to PPRF
 Nerves to extra-ocular muscles are engaged by fibres running through MLF

90
Q

hoe to keep straight gaze when head moves

A
  • slide 49: head move to right; left eye use lateral rectus (CN VI) and right eye use medial rectus (CN III) to keep straight gaze
    o via MLF
91
Q

damage to abducens VI causes

A
  • i.e. left eye damage causes them to look straight or deviate medially; cant abduct (bc lateral rectus compromised)

o right eye will look left from medial rectus
o causes: decreased depth perception, diplopia

BMS200 (46 decks)

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