Psych Test 5 (Vision)

Front 1

light

Back 1

- electromagnetic radiation
- for humans, light wavelengths 400-700 nm with max day sensitivity at 555 nm (middle of green range)
- violet: 400-450 nm
- red: 610-700 nm
- ultraviolet has shorter wavelengths than violet
- infrared has longer wavelengths than red
- humans can't see UV or red
- when we see an object, we are seeing light coming from it
- white light: combination of all frequencies between 400-700 nm

Front 2

sclera

Back 2

- white, tough outer wall of eye
- works with the rpessure of the eyes' internal fluid (vitreous humor) to keep eye shape and protect internal delicate structures

Front 3

cornea

Back 3

- clear round surface of transparent proetin sheet that covers front of eye
- 1st most powerful lens
- transparent because lacks blood vessels
- nourished by tears and aqueous humor behind it
- damageable

Front 4

iris

Back 4

- colored part
- ring of muscle fibers located behind cornea and in front of lens
- contracts/expands, opening and closing the pupil, in response to bright light

Front 5

pupil

Back 5

- black hole that light passes through

Front 6

lens

Back 6

- transparent protein structure
- behind cornea
- keeps images in focus on the retina
- adjustable for distance and close work, adjustments done by ciliary muscles

Front 7

ciliary muscles

Back 7

- relax to flatten the lens for distance vision and contract, rounding out the lens, for near vision
- lose elasticity with age, need reading glasses

Front 8

aqueous humor

Back 8

- water-like fluid that fills front of eye between lens and cornea
- provides lens/cornea with oxygen and nutrients

Front 9

vitreous humor

Back 9

- jelly-like fluid from lens to retina
- changes from gel to liquid with age and gradually shrinks, separating from retina => floaters (dark specks; cells that slough off of inner surface of eye)

Front 10

retina

Back 10

- layered sheet-like structure lining back of eye
- converts light into electrochemical nerve impulses and sends them to brain through optic nerve
- lateral sides for peripheral vision
- fovea- center, used for fine central detailed vision and color vision
- photoreceptors at back of retina to convert light to nerve impulses

Front 11

photoreceptors

Back 11

- sensory cells at the back of the retina that convert light into nerve impulses
- when light falls onto these cells, chemical reaction in photopigments that generates electrochemical pulses to be interpreted by nervous system
- 2 types of photoreceptors:: cone cells & rod cells

Front 12

cone cells

Back 12

- photoreceptor
- fine detail color daytime vision
- 6 million in each eye in fovea
- 3 types: sensitive to red light, green light, blue light
- require bright light to activate frequency specific photopigments

Front 13

rod cells

Back 13

- 500 times more sensitive to light than cone cells
- dim light or night vision
- more sensitive to motion
- 120 million per eye in side vision
- during bright light, the photopigments are bleached out/unable to function (ex. enter darkened room from bright light, hard to see due to bleaching out)
- dark adaptation: rod cell pigments are regenerated and dim light vision returns

Front 14

bipolar cells

Back 14

- in front of photoreceptor layer
- recieve input from photoreceptors and begin processing visual signal and pass info to ganglion cells (the 1st axon possessing nerve cells in retina)

Front 15

horizontal cells

Back 15

- link adjacent bipolar cells close to where bipolars contact photoreceptors

Front 16

amacrine cells

Back 16

- link adjacent bipolar cells where bipolars and retinal ganglion cells contact

Front 17

ganglion cells

Back 17

- front most cell in brain
- 1 million in eye
- compare signals from different photoreceptors, possible because horizontal/amacrine cells
- in the fovea area, ration of photoreceptor cell to bipolar cell to ganglion cell is 1:1:1
- in sides of retina, each ganglion cell is responsible for inputs of many photoreceptors
- axons of the ganglion cells come together to create optic nerve

Front 18

optic nerve

Back 18

- formed by axons of ganglion cells
- 1.2 million nerve fibers connecting eye to brain

Front 19

optic disk

Back 19

- blind spot
- spot on retina where optic nerve leaves the eye
- no sensory cells
- brain fills in misison info by process of approximation and comparing what stimuli surrounded the blind spot
- enters brain at optic chiasm

Front 20

optic chiasm

Back 20

- where optic nerve enters brain
- each eye takes different picture of the world and at optic chiasm, each picture is divided in half
- outer left/right halves cross to other side of brain then go back to visual cortex
- left side of external visual world processed entirely by right side of brain and right side of external visual world processed by left side of brain
- enters the brain as optic tract

Front 21

optic tract

Back 21

- connects optic chiasm to lateral geniculate nucleus (LGN) of the thalamus

Front 22

lateral geniculate nucleus
(LGN)

Back 22

- relay station doing only prelim decoding visual info from optic tract before sending it to visual cortex for final processing
- some inputs sent to optic tectum (superior colliculus) to guide eye movements and tracking moving objects with eyes

Front 23

visual cortex

Back 23

- takes up most of occipital lobe of brain
- processes and combines visual info to convert into sight
- several levels of cortex

Front 24

primary visual cortex
(V1)

Back 24

- does most basic general processing of visual world
- each column of cells responsible for small pixel element of visual scene
- damage results in cortical blindness

Front 25

other visual cortex areas
(V2, V3, V4, V5)

Back 25

- V2: coplex patterns generated from simpler patterns processed by V1
- V3: more detailed processing than V1 and processes movement
- V4: color and form like geometric shapes (more complex than V2)
- V5: processing form and motion

Front 26

dorsal stream

Back 26

- summed activity of Vs 1-5 further processed
- extends from occipital lobe to parietal
- allows us to understand "where" objects are in space or in relation to where out bodies are in space

Front 27

ventral stream

Back 27

- activity of visual cortex also set to ventral stream
- for determining "what" an object is
- specific faces, hands, and objects represented