ch. 6.2

  1. orbit
    the bony opening in the skull that houses the eyeball
  2. blink
    • rapid closing of eyelids
    • corrlated with less activity in the prefrontal cortex
  3. sclera
    • white outer covering of the eye
    • helps the fuilid filled eyeball maintin its shape
  4. cornea
    • the transparent outer layer of the eye
    • bc it's curved, it begins the process of bending/refracting light rays to form an image in the back of eye
    • clear, blood vessel-free extenseion of sclera (discouraged by proteins)
    • greater density of pain receptors than nearly any other part of body
  5. anterior chamber/aqueous humor
    area of eye located behind the cornea, contains AH

    the fluid that gives the cornea its nutrients
  6. pupil
    • the opening in the front of the eye controlled by iris
    • diameter is affected by emotional state
  7. iris
    • circular muscle in the front of eye that controls the opening of pupil
    • color is influenced by amount of melanin pigment
    • adjusts the opening of pupil in response to amount of light present in environment
  8. Lens
    • directly behind IRIS
    • helps focus the light on the retina in the back
    • trasnparent due to fiber organization/lack of blood vessels
    • depends on AQ
    • muscles attached to lens allows us to accomodate
  9. Accomodation
    the ability of lens to change shape to adjust to the distance of the visual stimulus
  10. Vitreous chamber/vitreous humor
    • the major interior chamber of eye
    • contains vitreous humor
    • VH the same one you were born with
  11. Retina
    • eleborate netowrk of photoreceptors and interneurons at the back of eye that is repsonsible for sensing light
    • image that is projected on R is upside down and reversed relative to actual orientation of object viewed
    • 3 layers of R
  12. Photoreceptors
    • Specialized sensory cell in the retina that responds to light
    • located in deepest layer of retina
    • before light reaches PR it must pass through VH, blood vessels, and neural layers
    • our visual system tunes out stimuli that remains constant (don't see vessels)
  13. Optic Nerve
    fiber pathway that is formed by axons of ganglion cells as they leave the eye
  14. Optic disk
    • area in retina where blood vessels and the optic nerve exit the eye
    • does not contains any PR (blind spot)
  15. Macula
    • a 6 mm round area in retina that is not covered by blood vessels and is specialized for detail version
    • responsible for central vision, not peripheral vision
  16. Central vision
    ability to perceive visual stimuli focused on the macula of the retina
  17. Peripheral vision
    the ability to perceive visual stimuli that are off to the side while looking straight ahead
  18. Fovea
    • center of macula, where the retina becomes thin and forms a pit (1.8mm)
    • specialized for detailed vision and contains only one type of PR (cones: permit vision in bright lights, exlcusive to primates)
  19. Epithelium
    • pigmented layer of cells that the retina is embedded in
    • support the PR and absorb random light (why interior of eye looks black when seen thru pupil)
    • camera flash: we see reflection of true red color of retina that results from rich blood supply, by reflecting light through eye a 2nd time, the odds of perceiving very dim lights at night are improved (white compound in nocturnal animals)
  20. Ganglion cell layer
    • layer of retinal interneurons farthest from the PRs
    • conains ganglion cells and gives rise to the optic nerve
    • each GC has a single axon, which form the optic nerve as it leaves retina
  21. Inner plexiform layer
    • dendrites of GCs form connections with the amacrine/bipolar cells OR
    • contiains axons/dendrites that connect the ganglion, bipolar, and amacrine cells
  22. Amacrine cell
    • retinal interneuron in the inner nuclear layer that integrates signals across adjacent segments of the retina
    • forms connections with BPs, GCs, and other ACs
    • processes movement
  23. Bipolar Cell
    • cell in inner nuclear layer of the retina that forms part of the straight pathways between PRs and GCs
    • receive input from PRs and HCs
    • communicate with Amacrine and GCs
    • produces graded potentials rather than action potentials
    • idenitifes contrast with receptive field
  24. Inner Nuclear Layer
    layer of retinal interneurons containing AMACRINE, BIPOLAR and HORIZONTAL cells
  25. Outer Plexiform Layer
    retinal layer containing axons and dendrites forming form connections between BIPOLAR cells hnwith horizontal cells and PRs
  26. Horizontal cells
    • retinal interneuron located in the inner nuclear lyaer that integrates signals from across the surface of the retina
    • receive input from PRs and provide output to bipolar cell
    • integrate info from PR that are close to one another
    • communicates thru formation of graded potentials
  27. Outer Nuclear Area
    in retina area that contains cell bodies of the PRs
  28. Rods/Scotopic vision
    • a PR that responds to low levels of light but not to color
    • SV: ability to see in dim light
    • long cylinder shaped outer segment containing large # of disks (contains rhodopsin)
    • no info on color, no sharp imges
  29. Outer segments
    • portion of PR containing photopigemnts
    • part of PR that absorbs light
    • gives Cones and Rods the shape/name
  30. Photopigments
    pigment contained in the PR of the eye that absorbs light
  31. Rhodopsin
    • the photopigment found in rods
    • allows rods to be 1000xs more sensitive to light than cones
    • absorbs photons most effectively at wavelenths of 502 nm (blueish green)
  32. Cones/Photopic vision
    • PR that operates in bright conditions and responds differentially to color
    • 6 million cones in the eye
    • PV: vision in bright light, sensitive to color and provides excellent clarity
    • outersegment of cone is shorter and more pointed than rods
    • stores 1 of 3 PHOTOPIGMENT in a folded membrance rather than in disks
  33. Transduction
    process of translating a physical stimulus into electrical signals that can be understood/processed by the nervous system
  34. Opsin/Retinal
    • Rhodopsin is made up of these 2 parts
    • protein chain/ chemical made from vitamin A
  35. 11-cis/all-trans
    • when retinal is bound to opsin in abesnece of light
    • form taken by retinal after ligth is absorbed by rod outer segment
  36. Dark Current
    the steady depolarization maintained by PRs when no light is present
  37. cGMP
    • 2nd messenger within PRs taht is responsible for maintaining the dark current by opening sodium channels
    • when rhodopsin molcules break apart after light, enzymes that break down cGMP are released so fewer sodium channels stay open so it becomes hyperpolarized
    • PRs release largest amounts of glutamate in the dark
  38. 3 types of CONES
    • blue/short WL: contains cyanolabe, 419 nm, violet
    • green/middle WL: contains chlorolabe, 531 nm, green
    • red/long WL: contains erythrolabe, 558 nm, yellow
  39. Receptive Field
    location on retina at which light affects the activity of a particular visual interneuron
  40. Lateral Inhibition
    • process in which active cells limit the activity of neighboring, less active cells
    • PRs/HCs limit the activity
    • produces sharpening/exaggeration of BPs responses to differences in light fallin on adjacent areas
    • identifies boundaries/edge
  41. Ganglion Cells
    • receives input from BP/ACs
    • forms action potentials, not silent
    • 1 million
  42. M cells
    • large cells that respond to all WLs regardless of color, subtle differences in contrast and stimuli that come and go rapidly
    • larger receptive fields
    • provides info about large low contrast moving objects
  43. P Cells
    • small and responds to high contrast and color
    • responds to particular color
  44. K cells
    • do not fit criterias for M and P cells
    • respond to blue and yellow
  45. optic chiasm
    area at base of brain where Optic nerves cross to from optic racts
  46. optic tracts
    fiber pathways between OC and destinations in the forebrain and brainstem
  47. Superior colliculus
    10% of axons in OT go to SC
  48. Lateral Geniculate Nucleus
    • 90& of OT axons form synapses here
    • 6 layers... first 2 are magnocellular layers: receive input from M cells
  49. Parvocellular laryers/Koniocellular layers
    • 4 dorsal alyers of the LGN that receive input from P cells
    • layers of small neurons between the larger 6 layers of LGN that receive input from K cells in ganglion layer
    • 80% of input to LGN comes from striate cortex, braintem reticular formation
  50. primary visual cortex/striate crotex
    occipital lobe for initial cortical analysis of visual input
Card Set
ch. 6.2
sturctures and functions of the visual system