chapter 2-the first steps in vision Flashcards Preview

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Flashcards in chapter 2-the first steps in vision Deck (72):
1

light

narrow band of electromagnetic radiation that can be conceptualized as a wave or a stream of photons

2

waves

property of light; color and reflection (and refraction)

3

photons

packets of energy/ligh
low light situations and absorbing

4

ray

light travels in particular direction

5

energy varies with

wavelength

6

visible light between ___ and ___ nm

400 (violet, more energy), 700 (red, less energy)

7

absorbed

energy that is taken up, not transmitted at all, necessary for detection

8

scattered

energy that is dispersed in an irregular fashion; less focused, atmosphere

9

reflected

energy that is redirected when it strikes a surface, needed to see nonlight sources

10

transmitted

energy that is passed on through a surface, without much alteration of direction

11

refracted

energy that is altered as it passes into another medium, focusing, good thing-lenses

12

cornea

front of eye, transparent cells (no blood vessels), refraction, transmitted

13

pupil

hole that light goes though, center of iris

14

iris

muscle that controls the width of pupil and the amount of light, absorbs light (not useful), reflect (eye color)

15

lens

transparent cells, refraction, control shape to focus

16

retina/fovea

sensation, absorb, transduction, location of photoreceptors

17

presbyopia

old age relatedd vision loss, stiffening of the lens

18

refraction is necessary to focus light rays onto the ___ and this is accomplished by the ____

retina, lens

19

accommodation

process in which lens changes its shape, altering its refractive power, focus image on retina, most useful for up close objects, moves image point forward

20

emmetropia

happy condition of no refractive error

21

way the lens refracts light causes point of focus of the image to be in front of or behind the retina

problems of refraction

22

myopia

nearshightedness, when light entering the eye is focused in front of the retina, and distant objects cannot be seen sharply
eyeball too long for given refractive power, too much power

23

hyperopia

when light entering the eye is focused behind the retina, farsightedness
eyeball is too short given refractive power, not enough power

24

accommodation cans what refraction problem

hyperopia

25

resolution

the ability of the eye to resolve fine spatial detail in the image

26

sensitivity

ability of the eye to respond at very low levels of retinal illumination

27

____ requires distinguishing between responses of nearby receptors; subtractive differentiation

resolution

28

___ is improved by summing responses across nearby photoreceptors; grouping things

sensitivity

29

photoreceptors

cells in the retina that initially transduce light energy into neural energy

30

rods

photoreceptors that are specialized for night vision; respond well in low luminance conditions, not process color

31

cones

photoreceptors that are specialized for daylight vision, fine visual acuity and color, best in high luminance conditions

32

center of the retina, packed full of cones

fovea

33

age related macular degeneration

central part of vision deteriorates

34

dry macular degeneration

less individual photoreceptors,

35

wet macular degeneration

wide loss of photoreceptors because of fluid release

36

bipolar cells

exist between photoreceptors and ganglion cell, transmits information; vertical movement

37

amacrine cells

makes synaptic contacts with bipolar cells and ganglion cells; spread horizontally; enhancement and temporal sensitivity

38

horizontal cells

lateral inhibition, influence overall light response

39

___ and ___ form lateral path in the retina

amacrine and horizontal cells

40

rod bipolars are all ___ cells, connect rods to ___ cells, and then connect to ON or OFF cone bipolars

ON, amacrine

41

ON bipolar cells

activated by the presence of light

42

OFF bipolar cells

activated by offset/absence of light

43

diffuse bipolar cell

spread out to receive input from multiple cones

44

midget bipolar cell

small, central in retina and receives input from 1 cone

45

property: photoreceptor type
fovea:
periphery

mostly cones
mostly rods

46

property: bipolar cell type
fovea
periphery

midget
diffuse

47

property: convergence
fovea
periphery

low (p ganglion cells)
high (m ganglion cells)

48

property: receptive field size
fovea
periphery

small
large

49

property: acuity (detail)
fovea
periphery

high
low

50

property: light sensitivity
fovea
periphery

low
high

51

convergence

idea of many into few, lots of rods into less ganglion cells

52

divergence

less onto many, cones

53

vertical pathway of retina

photoreceptors, bipolar cells, and ganglion cells

54

P ganglion cells

connect to the parvocellular pathway

55

parvocellular pathway

visual acuity, color and shape processing

56

temporal resolution

measurement with respect to time

57

finer resolution _____ in size with retinal eccentricity

increases

58

retinal eccentricity

the difference between the retinal image and the fovea

59

M ganglion cells

connect to the magnocellular pathway

60

magnocellular pathway

involved in motion processing

61

poor temporal resolution but good spatial resolution

P ganglion cells

62

good temporal resolution but poor spatial resolution

M ganglion cells

63

spatial resolution

pixels

64

receptive field

region of the retina in which stimuli influence a neurons firing rate, all the photoreceptors that will activate retinal ganglion cell

65

receptive fields are sensitive to

different intensity of light in the center and in the surround

66

light on receptive field

strong response

67

light off receptive field

weak response

68

center-surround receptive fields because luminance variations tend to be smooth within objects and sharp between objects, emphasize

object boundaries

69

retinal ___cells act like a filter for information coming into the brain

ganglion

70

center surround receptive fields most sensitive to ___ in the intensity of light

differences

71

looking at different from center and surround

resolution

72

sums across the center

sensitivity