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Neuroscience > Mod 11 Visual System > Flashcards

Mod 11 Visual System Flashcards

1
Q

What is a visual field?

A

the portion of space that can be viewed from the retina when the eye is fixated straight ahead (what we see in the environment)

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2
Q

What is a retinal field?

A

the portion of retina that alters its firing rate in reasons to a stimulus (picks up light and color)

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3
Q

What is the relationship between visual and retinal field?

A

reverse and inverted relationship (temporal visual field is the nasal retinal field)

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4
Q

How are visual deficits named?

A

according to visual field

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5
Q

How is the retina divided?

A
  • lateral: temporal
  • medial: nasal
  • superior and inferior half
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6
Q

What are rods and cones and where are they located?

A
  • deepest retinal layer
  • photoreceptors
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7
Q

What are the bipolar cells in the retina and where are they located?

A
  • intermediate retinal layer
  • info integrating neurons
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8
Q

What are the ganglion cells in the retina and where are they located?

A
  • superficial layer
  • info integrating neurons that exit the eyeball as the optic nerve (CN II)
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9
Q

What is the scotopic-rod system?

A
  • system that works at low levels of light and is sensitive to light, insensitive to color
  • limited resolution
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10
Q

What does the rod system help you do?

A

help see in the night vision

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11
Q

What is the photopic-cone system?

A
  • system that works at high levels of light and is responsible for seeing color, sharp vision, and acuity
  • color, clear
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12
Q

What color do rods see?

A

black, white, grey

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13
Q

What do rods and cones respond to?

A

respond to photons and signal retinal ganglion cells

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14
Q

How many rods and cones are in each eye?

A

80-110 million rods

4-5 million cones

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15
Q

Where are cones the densest in the eye?

A

densest in the macula

peripheral layers are where cones lie

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16
Q

What is the center of the macula?

A

fovea: area keenest vision

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17
Q

What is the memory trick remember cone’s role in the eye?

A

cones, color, clear

rods: light, peripheral

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18
Q

What is the role of ganglion cells in the eye?

A

center for retinal processing as it converges onto these cells

these cells form the optic nerve

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19
Q

Where do M Type ganglion cells project?

A

project to the magnocellular layer of the lateral geniculate body

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20
Q

What are M Type ganglion cells concerned with?

A

patterns and contrast

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21
Q

Where do P Type ganglion cells project?

A

parvocellular layer of lateral geniculate body

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22
Q

What are p type ganglion cells concerned with?

A

color transmission

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23
Q

What is the blind spot of the eye?

A

an elevated circular retinal region where ganglion cell axons leave the eye as the optic nerve

does not have rods and cones

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24
Q

What is the visual pathway?

A

receptors > bipolar cells(1st order) > ganglion cells (2nd order)/optic nerve > thalamus lateral geniculate body (3rd) > primary visual cortex

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25
Q

Which retinal field crosses in the optic chiasm?

A

nasal retinal fields

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26
Q

Which part of the nervous system is the optic nerve a part of?

A

CNS

27
Q

What is the structure of the optic nerve?

A
  • myelinated by oligodendrocytes
  • invested by dural sheet of CNS
  • surrounded by CSF
28
Q

Where do optic nerve fibers originate?

A

originate in ipsilateral eye

29
Q

What retinal fields are in a optic tract fiber?

A

temporal retinal field of ipsilateral eye and nasal retinal field of contralateral eye

30
Q

Where do most axons of the optic tract synapse?

A

on third order neurons in the lateral geniculate body of the thalamus

31
Q

Where does the LGB input come from?

A

10-20% from retina

rest comes from brainstem reticular info (arousal and consciousness) and visual cortex

32
Q

Where do third order neurons go?

A

project from the LGB as optic radiation to the occipital lobe

33
Q

Where do dorsal and ventral axons project in the brain?

A

dorsal: directly to occipital lobe

ventral: anteriorly and downward as Meyer’s loop

34
Q

What is the inversion of visual fields in the eye?

A

upper visual fields project to lower retinal quadrants

nasal to temporal

35
Q

Where does lower visual field input go in the visual pathway?

A

upper retinal quadrant goes dorsal to the primary visual cortex

36
Q

Where does upper visual field input go in the visual pathway?

A

lower retinal field goes to Meyer’s loop then PVC

37
Q

How do you remember what visual field goes to Meyer’s loop?

A

What I see higher goes meyer

38
Q

What does the calcarine sulcus do?

A

splits retinal field input

39
Q

Which broadmann’s area is the PVC?

A

BA 17

40
Q

Where do some optic radiation axons terminate?

A

un visual association cortex BA 18 and 19

41
Q

Where does the dorsal pathway of visual processing go and what does it process?

A
  • PVC to parieto-occipital cortex
  • WHERE in the visual field an event occurred
42
Q

Where does the ventral pathway of visual processing go and what does it process?

A
  • primary visual cortex to occipito-temporal cortex
  • WHAT the object in the visual field is
43
Q

Where do some optic tract axons terminate?

A

hypothalamus: role in circadian rhythm

44
Q

Why do some optic tract axons bypass the LGB and project to the midbrain?

A

superior coliculus: visual grasp reflex

pretectal area: visual light reflex

45
Q

How does aging affect the eye?

A

presbyopia develops
- age related loss of accommodation power (change focal length)
- lens hardens
- cannot focus on near objects

46
Q

What is age related macular degeneration?

A

6th decade of life
- loss of central vision and acuity
- affects cone system
- leading cause of blindness in elderly

47
Q

How do you assess the visual system?

A
  • snellen chart
  • ophthalmic inspection
  • pupillary light reflex
  • quadrant assessment
48
Q

What is found in ophthalmic inspection?

A

optic dic swelling with elevated intracranial pressure due to excessive CSF

can cause blurred, double, or transient full vision loss

49
Q

What is hemianopsia?

A

visual deficit of one-half of visual field
ex: temporal half

50
Q

What is quadrantanopsia ?

A

visual deficit of one quadrant of the visual field
ex: upper temporal quadrant

51
Q

What is bitemporal hemianopsia?

A

lesion to optic chiasm causing the loss of peripheral vision (severs nasal retinal fields)

52
Q

What is contralateral homonymous hemianopsia?

A

lesion impacting optic tracts
- cannot see temporal retinal field of ipsilateral eye and nasal retinal field of contralateral eye

53
Q

What is monocular scotoma?

A

individual blind spot

54
Q

What is monocular visual loss?

A

whole eye blindness

55
Q

What is contralateral inferior quadrantanopsia?

A

lower quadrant loss

56
Q

What is contralateral superior quadrantanopsia?

A

upper quadrant loss

57
Q

What is macular sparing?

A

vascular lesion to occipital lobe

  • both MCA and PCA nourish cortical area for macula
  • if one is occluded, the other still gives blood leaving you with central vision
58
Q

What is amaurosis fugax?

A

transient ischemic attack of the retina

59
Q

What is optic neuritis?

A

inflammatory demyelination disorder related to MS
- symptoms of: eye pain, decreased acuity, and impaired color vision, altered light reflex
- recovery is common

60
Q

What is visual agnosia?

A

deficit associated with higher cortical processing when you can perceive but not understand what you see (ventral pathway)

61
Q

What is prosopagnosia?

A

deficit associated with higher cortical processing that causes face blindness due to damage to the occipitotemporal cortex

62
Q

What are the first signs of MS?

A

optic neuritis, scotoma, and visual field deficits due to the loss of oligodendrocytes

63
Q

How do migraines connect with the visual pathway?

A

prodromal phase of migraine involves visual cortex
- 1/3 experience visual aura
- 10% experience scintillating scotoma where the blindspots are wavy, jagged, large, and bilateral in presentation

Neuroscience (15 decks)

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