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Perception Block 9 > Duplex Retina > Flashcards

Duplex Retina Flashcards

1
Q

A source with which of the following color temperature will appear most red

A

2000k

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2
Q

The color temperature of an incandescent bulb is 3300K. This means

A

The bulbs spectral distribution matches that of a blackbody radiator whose temperature is 3300K

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3
Q

A neutral density filter transmits 50% of 450nm light that is incident upon it. If 40W of 550nm are incident on the filter, how many watts are transmitted

A

20

40x50%=20W
Wavelengths doesn’t matter, it transmits all wavelengths equally

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4
Q

The least amount of distortion is present with sunglasses made with a

A

Neutral density filter

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5
Q

Which of the following light sources has more energy concetrated in the blue region of the spectrum

A

LEDs

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6
Q

What is the adaptional range of the human eye

A

10^-6 to 10^10

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7
Q

What makes it possible for the human eye to see something very bright and something very feeble in the night sky?

A

The pupil, but the pupil is good for only 1 log unit, the rest is from the retinal photoreceptors

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8
Q

How does pupil help make humans able to see bright and dark

A

By changing its diameter in response to light, helps to control the amount of light that falls upon the retina

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9
Q

How many log units does the pupil contribute to sensitivity of light

A

1 log unit

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10
Q

How can the eye adjust to a 10-log unit range of retinal luminance if the pupil can only account for 1 log

A

Retinal photoreceptors, rods and cones

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11
Q

Things about scotopic vision

A
  • sensitive to dim lights
  • poor VA
  • absence of color discrimination
  • mediated by rods
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12
Q

Photopic vision things

A
  • poor sensitivity to dim lights
  • excellent VA
  • color discrimination
  • cones mediate photopic vision
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13
Q

The existence of two classes of photoreceptors, each operating under different lighting conditions, referred to as a

A

Duplex retina

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14
Q

Under _____________conditions, both rods and cones contribute to vision

A

Mesopic conditions

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15
Q

Contained within the discs of the rods outer segment

A

Rhodopsin

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16
Q

One eye contains about ______ rods

A

120 mill

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17
Q

Each rod contains ______ disks

A

1000

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18
Q

Each disk within a rod contains ________rhodopsin molecules

A

10,000

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19
Q

How many rhodopsin molecules per eye

A

10^15

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20
Q

Each molecule of one rhodopsin is capable of absorbing ______ photon of light

A

One

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21
Q

The absorption of _____photon (s) is sufficient to activate a rod

A

One

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22
Q

The large number of rhodopsin molecules capture light and contributes to our exquisite _______ under nighttime lighting conditions

A

Sensitivity

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23
Q

The absoprtion of light quanta by the photosensitive pigment in the outer segment causes the photoreceptor to become ____________. This is the first step in a sequence of events that ultimately leads to vision.

A

Hyperpolarized

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24
Q

Light quanta that are incident on the rhodopsin, but not transmitted, have been ________

A

Absorbed

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25
Q

Relationship of the absoprtion curve and the transmission curve

A

Reciprocal

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26
Q

Light quanta of _______nm have the highest probability of absorption in rods

A

507nm

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27
Q

Wavelengths other than 507 in rods

A

Are absorbed, but with less probability

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28
Q

Once a quanta of light is absorbed, all information regarding its wavelength is lost, a principle referred to as ______________

A

Univariance

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29
Q

A molecule of rhodopsin becomes ______when it absorbs light

A

Bleached

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30
Q

The absoprtion of __________ is required to bleach a molecule of rhodopsin

A

One quantum of light

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31
Q

When a rhodopsin meolcule is in the bleached state, it is not capable of capturing another quantum, it will

A

Transmit a quantum of light incident on it

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32
Q

A bleached molecule will _________ to the unbleached state

A

Spontaneously revert back

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33
Q

50% of the rhodopsin will recover in 5 minutes. This is referred to as

A

The half life of rhodopsin

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34
Q

What is the half-life for rhodopsin

A

5 minutes

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35
Q

If you irradiate the retina with 1000 quanta of light at 507nm, you might successfully bleach _______ rhodopsin molecules

A

200 or 20%

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36
Q

If you irradiate the same part of the retina with 1000 quanta of light at 580nm, you might bleach _____ rhodopsin molecules, since the longer wavelength is absorbed less effectively

A

100

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37
Q

If you double the irradiance of 580nm light to 2000 quanta of light, you would bleach appx _______the number of rhodopsin molecules. This is equal to the result of bleaching the retina with 1000 quanta of 507nm light

A

Double the number (200)

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38
Q

Physiological response of the visual system to 1000 quanta of 507nm light and 2000 quanta of 680nm light

A

It is the same

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39
Q

Since the scotopic (rod) system produces one physiological response irrespective of wavelength, and it is possible to match the output signal for all wavelengths, by adjusting the brightness of the light. Therefore the scotopic system is _________; it has not wavelength discrimination

A

Colorblind

40
Q

Our ability to detect stimuli under scotopic conditions is circumscribed by the _________

A

Rhodopsin absorption curve

41
Q

Rhodopsin adsorption curve

A
  • Dark adapt someone for 45 minutes, maximizing the regeneration of the rhodopsin
  • the minimum amount of energy required for the person to detect stimuli of various wavelengths is determined.
42
Q

The minimum amount of energy required for detection of a stimulus is referred to as the _______ for that stimulus

A

Threshold

43
Q

The sensitivity curve is the ________ of the threshold function. A low threshold indicates a high sensitivity

A

Reciprocal

44
Q

What is human scotopic spectral sensitivity function determined by

A

The absorption characteristics of rhodopsin

45
Q

_______ is sufficient to activate one rod

A

One quanta absorption

46
Q

How many rods activate a ganglion cell

A

10

47
Q

How many ganglion cells needed for there to be detection

A

10

48
Q

For these 10 quantal absoprtion to result in detection, they must

A

Occur within certain space and time constraints

49
Q

_______ of the quanta incident on the retina are absorbed by rhodopsin

A

Fewer than 20%

50
Q

Is a stimulus that emits 10 quanta visible?

A

No because many quanta are either reflected or absorbed by tissues inner to the photoreceptors (preretinal and retinal) or not absorbed by rhodopsin

51
Q

What are the 3 cone pigments

A
  • cyanolabe/blue/426/S cone
  • chlorolabe/green/530/M cone
  • erythrolabe/red/557/L cone
52
Q

How many photopigments do each cone contain

A

One

53
Q

Where is the photopic spectral sensitivity

A

555

54
Q

Photopic spectral sensitivity shows a single broad peak in the region of

A

555nm

55
Q

What does the photopic spectral sensitivity curve represent

A

The addition of M and L cone absorption spectra

56
Q

S cones and the photopic spectral sensitivity

A

It is though that S cones make little, if any contribution to spectral sensitivity

57
Q

Where does the blue peek

A

Shorter than the rod (black line)

58
Q

The difference in sensitivity between scotopic and photopic systems, for a given wavelength is referred to as the

A

Photochromatic interval

59
Q

When is the photochromatic interval largest

A

At shorter wavelengths

60
Q

Where is the photochromatic interval medium

A

At medium wavelengths

61
Q

Where is the photochromatic interval switched, with the photopic being higher than the scotopic?

A

Longer wavelengths

62
Q

When does the photochromatic interval equal 0?

A

650nm

63
Q

When isthe photochromatic interval approximately zero and rods and cones are almost equally sensitive

A

Longer wavelengths

64
Q

Photochromatic interval beyond 650nm

A

The photopic system is slightly more sensitive than the scotopic system

65
Q

Photochromatic intervals ________with retinal eccentricity

A

Increase

66
Q

Photochromatic intervals int he fovea

A

Greatest for short, then medium, then long wavelengths

67
Q

Photochromatic wavelengths in the periphery

A

The order for short and medium wavelengths is reversed. The interval size for short and medium wavelengths increases at a negative rate and for long wavelengths at a positive rate

68
Q

Photochromatic intervals vary with

A

Stimulus size

69
Q

As lighting conditions change from scoptopic to photopic, the wavelength to which we are most sensitive increases from ______ to _____

A

507 to 555nm

70
Q

The relative increase in the brightness of longer wavelength stimuli as lighting conditions change from scoptopic to photopic

A

Purkinje shift

71
Q

How many rods in one eye

A

120 mill

72
Q

How many cones in one eye

A

6 mill

73
Q

What do the cones look like as you get further from the fovea

A

They get larger and mroe spaced out

74
Q

Ratio of L and M cones in people

A

Varies from person to person

75
Q

S cones distribution

A

Show a different retinal distribution than other cones. Not only are there considerably less numerous than either M or L ones, constituting appx 5-10% of the cone population, they are not found int he central 0.3-0.4 degrees of the human fovea

76
Q

What cones are not found in the fovea

A

S cones

77
Q

What cones are found in much less numbers in the retina

A

S cones

78
Q

Gradual improvement in vision, after exposure to bright-adapting light

A

Dark adaptation

79
Q

Rod and cone sensitivity recover

A

Recover at different rates, after exposure to bright lights

80
Q

What is recovery in sensitivity in rods and cones related to

A

The regeneration of photopigment molecules

81
Q

After 35 min in the dark, the eye is ______ more sensitive to light

A

100,000 times

82
Q

Cone plateau

A

10 minutes

83
Q

Rod-cone break

A

12 minutes

84
Q

From the point of cone plateau to the rod-cone break (10-12) minutes, what detects the stimulus

A

The cones

85
Q

Rod plateau

A

35 minutes

86
Q

Where does the rod cone break occur

A

At that point in time when the rods become more sensitive than the cones

87
Q

When do rods become more sensitive than cones

A

Rod-cone break, 90% of the rhodopsin as regenerated

88
Q

The different between the cone plateau, which represents the minimum photopic threshold for a stimulus, and the rod plateau, which represents the minimum scotopic threshold for this same stimulus

A

Photochromatic interval

89
Q

The photochromatic interaval is about ____ log units

A

3

90
Q

Bleaching to rod recovery is about ____ log units

A

5

91
Q

After _____ log units, sensitivity for rods increases

A

5

92
Q

What form does the dark adaptation curve take if the stimulus is 650nm?

A

It shows only oa cone portion, the rod aspect is missing, since the photochromatic interval for 650nm is 0. And because the scotopic system is not more sensitive than the photopic system, there is not an obvious rod-cone break

93
Q

The photochromatic interval for the 420nm stimulus

A

Large, consequently, this stimulus produces a dark adaptation curve with a prominent rod-cone break

94
Q

____ are not mroe sensitive than ____ for long wavelengths

A

Rods

Cones

95
Q

The stimulus used to generate the dark adaption curve

A

Is large and central fixeted. Such a stimumuls falls on both the fovea and surrounding retina

96
Q

What happens when you make the stimulus small when doing dark adaptation

A

Only a cone function is obtains, the absence of a rod function reflects the absence of rods in the fovea.

Perception Block 9 (5 decks)

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