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NEURO 3000 > ch. 9 - eye > Flashcards

ch. 9 - eye Flashcards

1
Q

wavelength

A

distance between peaks

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2
Q

frequency

A

waves per second

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3
Q

amplitude

A

peak minus through

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4
Q

what is the visual range for humans?

A

400-700 nm

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5
Q

higher frequency equals…

A

higher energy

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6
Q

optics

A

the study of light rays and their interactions

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7
Q

ray

A

wave of electromagnetic radiation in vacuum traveling as a straight line

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8
Q

reflection

A

the bouncing of light rays off a surface; this is most of the light we see

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9
Q

absorption

A

transfer of light energy to a particle or surface

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10
Q

refraction

A

the bending of light rays that can occur when they travel from one transparent medium to another

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11
Q

pupil

A

opening that allows light to enter the eye and reach the retina; dark because of retinal pigments

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12
Q

iris

A

pigmentation provides the eye color

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13
Q

muscles around iris

A

control pupil size

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14
Q

cornea

A

transparent external surface that contains NO blood vessels

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15
Q

sclera

A

the white of the eye, forms the tough wall of the eyeball

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16
Q

extraocular muscles

A

move the eyeball in orbit (three pairs)

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17
Q

conjunctiva

A

a membrane that folds back from the inside of the eyelids and attaches to the sclera

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18
Q

optic nerve

A

carries axons from the retina and exits the back of the eye, passes through the orbit, and reaches the base of the brain by the pituitary gland

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19
Q

optic disc

A

where the optic nerve fibers exit the retina; there are blood vessels here; form blind spot

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20
Q

macula

A

the part of the retina for central vision

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21
Q

fovea

A

retina is the most thin here; good reference point

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22
Q

ophthalmoscope

A

a device that enables one to peer into the eye through the pupil to the retina

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23
Q

ciliary muscles

A

attached to the sclera; controls shape of the lens

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24
Q

aqueous humor

A

watery fluid that lies between the cornea and the lens

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25
Q

vitreous humor

A

lies between the lens and the retina; its pressure serves to keep the eyeball spherical

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26
Q

esotropia

A

cross-eyed

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27
Q

exotropia

A

wall-eyed

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28
Q

extraocular muscle disorders

A

input from one eye is suppressed

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29
Q

cataract

A

clouding of lens

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30
Q

glaucoma

A

increased intraocular pressure

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31
Q

retinitis pigmentosa

A

loss of peripheral and night vision

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32
Q

macular degeneration

A

loss of central vision

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33
Q

where is the site of most of the refractive power of the eyes?

A

cornea

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34
Q

what is the reactive power of the cornea?

A

42 diopters

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35
Q

what is the focal distance of the cornea?

A

2.4 cm (or 0.024m)

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36
Q

focal distance

A

the distance from the refractive surface to the point where parallel light rays converge

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37
Q

the tighter the curve of the cornea, the _____ the distance.

A

shorter

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38
Q

what does refractive power depend on?

A

the slowing of light at the air-cornea interface

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39
Q

accommodation

A

changing the shape of the lens; ciliary muscles contract, lens becomes more round, more curved

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40
Q

hyeropia

A

far-sightedness, convex

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41
Q

myopia

A

near-sightedness, concave

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42
Q

detached retina

A

retina pulls away from underlying wall of the eye from a blow to the head or by shrinkage of the vitreous humor

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43
Q

pupillary light reflex

A

produced by retina-brain stem connections

* consensual

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44
Q

construction of pupil…

A

increases depth of focus

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45
Q

visual acuity

A

ability to distinguish between near by points

20/20 = 0/083 degrees

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46
Q

left visual field is imaged on what side of the retina?

A

RIGHT

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47
Q

right visual field is imaged on what side of the retina?

A

left

48
Q

what is the most direct pathway for visual info. to exit the eye?

A

photoreceptors to bipolar cells to ganglion cells

49
Q

horizontal cells

A

receive input from photoreceptors and project neuritis laterally to influence surrounding bipolar cells and photoreceptors

50
Q

amacrine cells

A

receive input from bipolar cells and project laterally to influence surrounding ganglion cells, bipolar cells, and other amacrine cells

51
Q

what are the ONLY light sensitive cells in the retina?

A

photoreceptors

52
Q

what are the ONLY source of output from the retina?

A

ganglion cells

53
Q

how is the retina organized?

A

in layers (laminar)

54
Q

how does light pass?

A

from vitreous humor through ganglion and bipolar cells BEFORE it reaches photoreceptors

55
Q

what is the innermost layer of the retina?

A

ganglion cell layer

56
Q

what is the second layer of the retina?

A

inner nuclear layer: bipolar, horizontal, and amacrine cells

57
Q

what is the third layer of the retina?

A

outer nuclear layer: cell bodies of photoreceptors

58
Q

what is the last layer of the retina?

A

layer of photoreceptor outer segments: light sensitive elements

59
Q

pigmented epithelium

A

lies below the photoreceptors, plays a critical role in the maintenance of the photoreceptors and photopigments

60
Q

inner plexiform layer

A

between the ganglion cell and inner nuclear cell layers, contains the synaptic contacts between bipolar, amacrine, and ganglion cells

61
Q

outer plexiform layer

A

between the outer and inner nuclear layers, where photoreceptors make synaptic contact with the bipolar and horizontal cells

62
Q

rod photoreceptors

A

long, cylindrical outer segment, containing many discs

63
Q

cone photoreceptors

A

shorter, tapering outer segment with fewer discs

64
Q

night vision (scotopic)

A

rods bc they are 1000X more sensitive

65
Q

dayligt (photopic)

A

cones

66
Q

does the peripheral retina have more rods or cones?

A

RODS

67
Q

T or F: peripheral retina has more receptors per ganglion cell

A

true

68
Q

is the peripheral retina more sensitive to light?

A

yes, bc rods are specialized for low lights and there are more photoreceptors feeding info to each ganglion cell

69
Q

what area is specialized for high resolution?

A

fovea bc there are no rods

70
Q

is the peripheral retina good for details?

A

NO, it is poor for details

71
Q

__X more rods than cones

A

20

72
Q

what is the Vm of the rod outer segment?

A

-30 mV

73
Q

dark current

A

Vm due to special Na+ channels, opened by cGMP, made by guanylate cyclase

74
Q

in light

A

light reduces levels of cGMP, Na+ channels close, photoreceptor cells hyperpolarize

75
Q

what is light absorbed by in rod outer segment?

A

rhodopsin

76
Q

receptor is phototransduction

A

opsin

  • 7 TM G-protein receptor
  • retinal bound
77
Q

retinal

A

a derivative of vitamin A

78
Q

bleaching

A

the absorption of light causes a change in the conformation of retinal so that it activates opsin

79
Q

what does bleaching stimulate?

A

the G-protein transductin, which then activates phosphodiesterase (PDE) - which breaks down cGMP

80
Q

amplification

A

allows detection of single photon

81
Q

at what wavelength do rods respond to light?

A

500 nm

82
Q

what does it mean when light becomes saturated?

A

additional light causes no more hyperpolarization

83
Q

at what wavelength are blue cones maximally activated?

A

430 nm

84
Q

at what wavelength are green cones maximally activated?

A

530 nm

85
Q

at what wavelength are red cones maximally activated?

A

560 nm

86
Q

what did young show about colors?

A

all colors of the rainbow, including white, could be created by mixing the proper ratio of red, green, and blue light

87
Q

young-helmholtz trichromacy theory

A

the brain assigns colors based on comparison of the readout of the three cone types

88
Q

dark adaptation

A

getting used to the dark, takes about 20-25 mins

89
Q

what is dark adaptation due to?

A
  • pupil dilation
  • adjustment of retinal circuitry
  • making new unbleached rhodopsin
90
Q

light adaptation

A

reversing the changes in the retina that were accomplished by dark adaptation, takes 5-10 mins

91
Q

what is Ca2+ role in light adaptation?

A
  • inhibits guanylyl cyclase

- decreases PDE and photopigments response to light

92
Q

who were the neuropysiologists behind retinal processing?

A

Hartline, Kuffler, and Barlow (1950)

93
Q

what did they find with retinal processing?

A

ONLY ganglion cells fire action potentials

94
Q

what did Dowling find in 1970s?

A

how retinal ganglion cells responses were affected by horizontal and bipolar cells

95
Q

OFF-type bipolar cells

A

glutamate gated cation channels mediate a classical depolarizing EPSP from the influx of Na+

  • “sign conserving”
  • depolarize in dark
  • hyperpolarize in light
96
Q

ON-type bipolar cells

A

have G-protein-coupled receptors and respond to less glutamate

  • “sign inverting”
  • depolarize in light
  • hyperpolarize in dark
97
Q

receptive field

A

area of retina that when stimulated with light changes the cell’s membrane potential

98
Q

receptive field center

A

a circular area of retina providing direct photoreceptor input

99
Q

receptive field surround

A

surrounding area of retina providing input via horizontal cells

100
Q

1 mm on the retina is how many degrees?

A

3.5

101
Q

ON response

A

illumination of the center causes depolarization, while illumination of the surround will causes antagonistic hyoerpolarization

102
Q

OFF response

A

cell is depolarized by a spot turning from light to dark in the center, it will be hyperpolarized by the same stimulus to the surround

103
Q

ON center ganglion cells

A

is depolarized and responds with a barrage of action potentials when a small spot of light is projected onto the middle of its receptive field

104
Q

what are ganglion cells most responsive to?

A

differences in illumination that occur within their receptive field

105
Q

uniform illumination

A

the center and surround cancel to yield some low level response

106
Q

P ganglion cells

A
  • 90%
  • contact one to a few cone bipolar cells
  • small cells
  • small concentric receptive field
  • sustained
  • slowly adapting response
  • weak response to movement
107
Q

M ganglion cells

A
  • 5%
  • synapse with many bipolar cells
  • color insensitive
  • large concentric receptor field
  • transient
  • rapid adapting response
  • responds to movement across field
108
Q

non M - non P cells

A

other 5%

109
Q

which ganglion cells are sensitive to color?

A

P and some nonM-nonP

110
Q

color-opponent cells

A

response in center to one wavelength is canceled by other wavelength in surround

111
Q

red-green

A

P cells

112
Q

blue-yellow

A

nonM-nonP

113
Q

parallel processing

A
  • information about depth
  • light and dark information
  • ganglion cells have different receptive fields and response properties
114
Q

low resolution, large field

A

M cells

115
Q

small fields, fine detail

A

P cells

NEURO 3000 (16 decks)

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