2 - Vision Flashcards

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1
Q

Back of Eye

A
  • Sclera: White of eye; thick - gives structure
  • Choroid - blood vessel layer
  • Retina- inner layer, back of eye, photoreceptors, leads to optic nerve
  • Cats- tapida lucidum- green eyes- reflective layer
  • Red eye phenomena- bright flash, see vasculature
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2
Q

Front of Eye

A
  • Cornea- front, clear- contact lens goes here, light enters here- refract/focus into lens
  • Iris- colored part of eye, PAIR of muscles: dilator pupillae & constrictor pupillae
  • Lens- behind iris, refracts light into retina

Anterior chamber- in front of iris
Posterior chamber- in front of lens, behind iris- makes aqueous humor (specifically ciliary body)

  • Canal of Schlemm- allows aqueous humor (front, clearer than vitreous) to drain out
  • –if blocked, at risk of GLAUCOMA (eye pressure = damage optic nerve)
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3
Q

Middle of eye

A
  • Ciliary muscles- attached to lens via zonular fibers/suspensory ligaments- stretch/constrict lens to focus light in dif ways- near vs far
  • —as you get older, lens stiffer + muscles don’t work as well = farsightedness, harder reading = bifocals; presbyopia

-Vitreous humor = behind lens; transparent gel; eye shape + support retina—— look at neutral background, squiggles floating around in vision- floaters = bits of protein/cells- harmless, float around in v. humor

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4
Q

Path of info into eye

A
  • Lens refraction- inverted image projected onto retina
  • the brain does NOT receive an inverted image and flip it right side up; it simply gets the info and assembles it the right way
  • physics review- real image is where rays converge; virtual image is where rays appear to diverge; real images are inverted
  • review optics notes you made :)
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5
Q

Duplicity

A

duplex theory of retina
2 photoreceptors: rods (light/dark) and cones (color)

Cones- fine detail, bright light- 3 types based on wavelength that they best absorb light
S/short= blue; M/medium = green; L/long = red
400 nm, 550 nm, 700 nm
6 million cones

Rods- less detail/low resolution, night vision/low light, single pigment = rhodopsin
120M rods

Cones restricted almost exclusively to fovea (middle of retina)

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6
Q

Macula

A
  • middle of retina
  • separates peripheral and central vision (central inside)
  • zones
  • dark portion inside macula is FOVEA— cones + strongest visual acuity (sharpness of vision)

-You can survive w/o peripheral vision (only reflexes affected); macular degeneration = lose central vision = blind

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7
Q

Peripheral vision

A
  • our peripheral vision isn’t that strong- less accurate/resolute/saturated(color)
  • grayscale; but we perceive color b/c we expect objects to not change color
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8
Q

Optic disk

A

Blind spot
-no photoreceptors
-optic nerve which photoreceptors connect to
photoreceptors - bipolar cells- ganglion cells - optic nerve

-it’s not that your brain is filling in the info; it’s that your brain is just not looking for info there

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9
Q

Light path w/in eye

A
  • not all the light that travels through the lens makes it through retina
  • light must go through retina/ganglion cells/bipolar cells to reach photoreceptors
  • multiple rods wired to one bipolar cell = low resolution
  • cones - 1 cone : 1 bipolar cell- more accurate
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10
Q

Light path eye to brain

A
  • Light from eyes to optic nerve to OPTIC CHIASM (some optic nerve fibers from one eye cross optic nerve fibers from other eye)
  • to optic tract to THALAMUS (Lateral geniculate nucleus in thalamus)
  • **LGN organizes info based on depth, motion, shape/form, color (“mail room”) through optic tract still
  • to occipital lobe/visual cortex

object in right visual field = left retina of both eyes, left LGN, left occipital

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11
Q

An example w/ broccoli bc why not

A
  • Broccoli on right side of head = light rays hit left side of visual field
  • Signals from LH side of both visual fields of eye go to left side of brain, to LEFT LGN to left part of occipital lobe

-Optic chiasm is where the nasal visual fields (nerves of inside of each eye/medial) cross path/ decussate

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12
Q

Visual cortex

A

FEATURE DETECTORS

  • in cerebral cortex, in occipital lobe
  • back of brain
  • visual cortex contains feature detectors
    ex) things that respond to lines like divisions of shapes in the world that are oriented horizontally, or vertical
  • when you sense shapes/outlines- cells in both LGN (reorganize info) and visual cortex fire based on where those contours are
    ex) fire when something moves left to right, or R to L
  • in visual cortex, signals are so well organized that researchers can take signals from visual cortex after projecting image on display & reproduce it on another display = RETINOTOPIC MAP
  • if you look at visual cortex & where info is, it corresponds to where info is in environment = you get a pic of what’s going on in cortex in retinotopic map
  • from here, signal sent to rest of cerebral cortex, to association areas- reason & respond to it
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13
Q

Summary of pathway eye to brain

A

Eyes - LGN of thalamus (reorganize/repackage info) - to visual cortex of occipital lobe (a lot of analysis) - to cerebral cortex (thinky stuff goes on)

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14
Q

Processing

A
  • processing in sequences takes too long; do PARALLEL PROCESSING
    ex) allows for good hand-eye coordination; fraction-of-second reaction

(in sequence = process colors, then shapes, then motion, etc)
-perception of env would lag behind env

Parallel processing - brain takes info / signal and processes the various parts of it in different places at the same time = FASTER

  • Color processed by cones (dif cones respond to different wavelengths of light)
  • Shape - in thalamus’s LGN —> its PARVOCELLULAR CELLS (parvo = small)- high color spatial resolution = see fine detail; but low temporal resolution = only w/ immobile/slow-moving objects
  • *this is why things appear blurry when moving really quickly
  • Motion - magnocellular cells of thalamus (Magno = large) - high temporal resolution- can tell when things are moving, but can’t necessarily distinguish individual shapes (high temporal resolution but low spatial resolution)

-then all info sent to occipital lobe at same time; process there; BOOM you’re done

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