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SEM 2 Sensation & Perception > The eye and retina > Flashcards

The eye and retina Flashcards

1
Q

What is a distal stimulus?

A

A physical object in the environment

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2
Q

Which cells carry out transduction?

A

Receptor cells

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3
Q

Why is knowledge important in perception?

A

Top-down processing

Perception is a complex process

Knowledge can help simplify perception

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4
Q

What is an absolute threshold?

A

The minimum quantity of something we can detect

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5
Q

When we can perceive physical stimuli in the environment because of light, what is this known as in the perceptual process?

A

Distal stimulus

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6
Q

Define light

A

Light is a form of electromagnetic energy

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7
Q

A form of electromagnetic energy

A

Light

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8
Q

Light varies in 2 physical dimensions. What are they?

A

1) Wavelength
2) Intensity

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9
Q

Light varies in 2 psychological dimensions. What are they?

A

1) Colour
2) Brightness

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10
Q

Does light wavelength relate to brightness or colour?

a. Brightness
b. Colour

A

b. Colour

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11
Q

Does light intensity relate to brightness or colour?

a. Brightness
b. Colour

A

a. Brightness

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12
Q

On the electromagnetic spectrum, what wavelength of light can we see with our human eye?

A

Visible spectrum

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13
Q

True or False?

Light is absorbed from objects and into the eye

A

False
Light is reflected from objects and into the eye

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14
Q

When we can perceive physical stimuli after light reflects from objects and into the eye, what is this known as in the perceptual process?

A

Proximal stimulus

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15
Q

What is located inside the retina that allows for transduction?

A

Receptors

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16
Q

True or False?

Receptors are located in the retina

A

True

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17
Q

What is the function of the eye?

A

The function of the eye is to focus the image on the retina

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18
Q

What is the iris?

A

The coloured part of the eye (brown, blue, green)

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19
Q

What is the pupil?

A

The black circle inside the iris

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20
Q

The coloured part of the eye (brown, blue, green)

What is this?

A

The iris

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21
Q

What are the 3 main purposes of the iris and pupil?

A

1) Adjustable aperture
2) Limit the amount of light passing through
3) Allows us to deal with a great range of light levels

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22
Q

How wide is the pupil?

A

Pupil is between 2 mm and 9 mm in diameter

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23
Q

What is the shared role between the cornea and lens?

A

The role is to focus light on the retina

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24
Q

The role is to focus light on the retina

What part(s) of the eye is responsible for this role?

A

Cornea and Lens

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25
Q

1) Adjustable aperture
2) Limit the amount of light passing through
3) Allows us to deal with a great range of light levels

What part(s) of the eye is responsible for this role?

A

Iris and Pupil

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26
Q

The outer surface of the eye, which is transparent, is called…?

A

Cornea

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27
Q

The cornea has ……..% focusing power

A

80%

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28
Q

The lens has ….% focusing power

A

20%

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29
Q

Has 80% focusing power

What part(s) of the eye is responsible for this role?

A

Cornea

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30
Q

What part(s) of the eye is responsible for this role?

Shaped like a dome and bends light to help the eye focus

A

Cornea

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31
Q

Some of the light enters the eye through an opening called the ……?

A

Pupil

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32
Q

What part(s) of the eye is responsible for this role?

Controls how much light the pupil lets in

A

Iris

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33
Q

What part(s) of the eye is responsible for this role?

Changes in shape due to the action of ciliary muscles

A

Lens

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34
Q

What allows the lens to change its shape?

A

The contraction or relaxation of the ciliary muscles

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35
Q

Why do lenses change shape?

A

To focus on objects at various distances (changes the amount of focusing power)

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36
Q

As the distance of an object varies, what is the name of the process where the eye changes the focal length of the lens by changing the curvature of the lens?

A

Accommodation

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37
Q

Define accommodation

A

As the distance of an object varies, the eye changes the focal length of the lens by changing the curvature of the lens

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38
Q

When the eye focuses on closer objects, does the lens…?

a. Become fatter
b. Become thinner

A

a. Become fatter

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39
Q

When the eye focuses on far objects, does the lens…?

a. Become fatter
b. Become thinner

A

b. Become thinner

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40
Q

Why does the lens become fatter when attempting to focus on near objects?

A

To allow the light rays to refract (bend) more strongly

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41
Q

Why does the lens become thinner when attempting to focus on far objects?

A

To allow the light rays to refract (bend) only a little bit/slightly

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42
Q

What are the 2 types of refractive errors?

A

1) Myopia
2) Hyperopia

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43
Q

What is Myopia in simple terms?

A

Nearsightedness

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44
Q

What is hyperopia in simple terms?

A

Farsightedness

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45
Q

What results in myopia?

A
  • The eye focuses light in front of your retina instead of onto it
  • The retina is the surface at the back of your eye that collects light and changes the light into electrical impulses that your brain reads as images
  • When the eye focuses light in front of the retina, it can result in blurred vision for far away objects
  • It is likely that the eyeball is a little too long (oval-shaped rather than round) or the cornea is too rounded = light rays bend too much
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46
Q

What results in hyperopia?

A
  • The eye focuses light behind your retina instead of onto it
  • The retina is the surface at the back of your eye that collects light and changes the light into electrical impulses that your brain reads as images
  • When the eye focuses light behind the retina, it can result in blurred vision for near objects
  • It is likely that the eyeball is a little too short than normal and the cornea is overly flattened = light rays bend too little
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47
Q

People with myopia must wear what type of lens for their glasses?

A

Concave lens

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48
Q

People with hyperopia must wear what type of lens for their glasses?

A

Convex lens

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49
Q

How do concave lenses correct myopia?

A

Allows the light entering the lens to diverge so that it will correctly focus on the retina

The concave lens pushes the rays of light further apart so that they arrive together in proper focus at the back of the eye

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50
Q

How do convex lenses correct hyperopia?

A

Allows the light entering the lens to converge so that it will correctly focus on the retina

The convex lens brings the rays of light closer together so that they arrive together in proper focus at the back of the eye

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51
Q

Which lens is thicker in the middle?

a. Concave
b. Convex

A

b. Convex

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52
Q

Which lens is thinner in the middle?

a. Concave
b. Convex

A

a. Concave

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53
Q

Light- (photo-) sensitive layer at the back of the eye

This is known as…?

A

The retina

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54
Q

Define the retina

A

Light- (photo-) sensitive layer at the back of the eye

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55
Q

What are the 6 different types of cells in the retina?

A

1) Optic nerve
2) Retinal ganglion cells
3) Amacrine cells
4) Bipolar cells
5) Horizontal cells
6) Photoreceptors

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56
Q

What part of the eye contains:

1) Optic nerve
2) Retinal ganglion cells
3) Amacrine cells
4) Bipolar cells
5) Horizontal cells
6) Photoreceptors

A

Retina

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57
Q

Light-sensitive cells are known as…?

A

Photoreceptors

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58
Q

What cells turn light into electrical impulses?

A

Photoreceptors

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59
Q

Photoreceptors turn light into electrical impulses. What is the name of this process?

A

Transduction

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60
Q

Define Transduction

A

When photoreceptors turn light into electrical impulses

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61
Q

What cells carry out transduction?

A

Photoreceptors

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62
Q

Define photoreceptors

A

Light sensitive cells

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63
Q

How does transduction occur?

A

Visual photopigments react to light and trigger electrical signals

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64
Q

What are the 2 types of photoreceptors?

A

1) Rods
2) Cones

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65
Q

Which is longer?

a. Rods
b. Cones

A

a. Rods

66
Q

Which has a head that has a similar shape to a leaf?

a. Rods
b. Cones

A

b. Cones

67
Q

Which has a head that has a similar shape to a comb (rectangle head)?

a. Rods
b. Cones

A

a. Rods

68
Q

Which is shorter?

a. Rods
b. Cones

A

b. Cones

69
Q

Which has more in the retina?

a. Rods
b. Cones

A

a. Rods

70
Q

Which has less in the retina?

a. Rods
b. Cones

A

b. Cones

71
Q

How many rods are there in the retina?

A

120 million in each retina

72
Q

How many cones are there in the retina?

A

6 million in each retina

73
Q

Rodes and Cones differ in terms of…? List 5 differences

A
  • Number
  • Sensitivity
  • Involvement in colour perception
  • Retinal distribution
  • Neural convergence & acuity
74
Q

Which photoreceptor is more sensitive?

a. Rods
b. Cones

A

a. Rods

75
Q

Which photoreceptor works really well in dim light and at night?

a. Rods
b. Cones

A

a. Rods

76
Q

Which photoreceptor is more useful in daylight?

a. Rods
b. Cones

A

b. Cones

77
Q

Which photoreceptor is less sensitive?

a. Rods
b. Cones

A

b. Cones

78
Q

Which photoreceptor is better at picking up low levels of light?

a. Rods
b. Cones

A

a. Rods

79
Q

Which photoreceptor is useless at night?

a. Rods
b. Cones

A

b. Cones

80
Q

Which photoreceptor is useless in daylight?

a. Rods
b. Cones

A

a. Rods

81
Q

What is scotopic vision regime/sensitivity?

A

When only rods are active in the retina

82
Q

What is photopic vision regime/sensitivity?

A

When only cones are active in the retina

83
Q

What is mesopic vision regime/sensitivity?

A

When both rods and cones are active in the retina

84
Q

When only cones are active in the retina

Is this…?
a. Scotopic
b. Photopic
c. Mesopic

A

b. Photopic

85
Q

When both rods and cones are active in the retina

Is this…?
a. Scotopic
b. Photopic
c. Mesopic

A

c. Mesopic

86
Q

When only rods are active in the retina

Is this…?
a. Scotopic
b. Photopic
c. Mesopic

A

a. Scotopic

87
Q

Where there’s no moon or sun (dim/dark light) outside.

What vision regime is used?
a. Scotopic
b. Photopic
c. Mesopic

A

a. Scotopic (only rods are active)

88
Q

Where there’s moonlight or early twilight (some light) outside.

What vision regime is used?
a. Scotopic
b. Photopic
c. Mesopic

A

c. Mesopic (both rods and cones are active)

89
Q

Where there’s full sunlight (a lot of light) outside.

What vision regime is used?
a. Scotopic
b. Photopic
c. Mesopic

A

b. Photopic

90
Q

When do photoreceptors stop responding?

A

When there is bright light

Bright light bleaches photopigments so photoreceptors stop responding

91
Q

An increase in the eye’s sensitivity in the dark is known as…?

A

Dark adaptation

92
Q

Define dark adaptation

A

An increase in the eye’s sensitivity in the dark

93
Q

Going from bright to dark allows photoreceptors to do what?

A

To “recover” or regain sensitivity after having their photopigments bleached from bright light

94
Q

The process whereby the retina adapts to decreasing levels of illumination is…?

A

Dark adaptation

95
Q

Which process entails a transition from a cone to a rod activity, and thus a change in light sensitivity?

A

Dark adaptation

96
Q

After 20-30 minutes in the dark, sensitivity is about (………..) times greater than the sensitivity in light

A

100,000

97
Q

Transitioning from being in the light from outside and coming into a dark room, do cones adapt at a fast or slow rate?

A

Fast

Because it doesn’t take that long for them to adapt from low sensitivity to a slightly higher sensitivity

Cones are already low in sensitivity so it doesn’t take that long to return back to their normal low sensitivity

98
Q

Transitioning from being in the light from outside and coming into a dark room, do rods adapt at a fast or slow rate?

A

Slow

Because it takes them a while to adapt from low sensitivity to a much higher sensitivity

Rods are originally high in sensitivity so it takes longer to return back to their normal high sensitivity from low sensitivity

99
Q

Which photoreceptor adapts to the dark after being in the light faster?

A

Cones

100
Q

Which photoreceptor adapts to the dark after being in the light slower?

A

Rods

101
Q

Which photoreceptor is responsible for colour vision?

A

Cones

102
Q

Cones are responsible for…?

A

Colour vision

103
Q

What are the 3 types of cones (each sensitive to different wavelengths of light)?

A

1) Red (long wavelengths)
2) Green (medium wavelengths)
3) Blue (short wavelengths)

104
Q

Which type of cone has a long wavelength?

A

Red

105
Q

Which type of cone has a long medium wavelength?

A

Green

106
Q

Which type of cone has a short wavelength?

A

Blue

107
Q

Which type of cone is blue?

A

Short wavelength

108
Q

Which type of cone is green?

A

Medium wavelength

109
Q

Which type of cone is red?

A

Long wavelength

110
Q

Which photoreceptor produces monochromatic vision?

A

Rods

111
Q

What kind of vision do rods produce?

A

Monochromatic vision

112
Q

Rods only have 1 type. What wavelength is it sensitive to?

A

Most sensitive to medium wavelengths (green light)

113
Q

What is it called when the peak luminance sensitivity of the eye shifts toward the blue end of the colour spectrum at low illumination levels as part of dark adaptation?

A

Purkinje shift

114
Q

At night red looks darker than green. This is known as…?

A

Purkinje shift

115
Q

Define Purkinje shift

A

At night, the cones are not working so only the rods are working

Rods produce monochromatic vision and are sensitive to blue-green (between short-medium wavelengths)

Because rods are sensitive to blue-green (between short-medium wavelengths), red (longer wavelengths) will appear darker, whereas blues and greens (shorter wavelengths) will appear brighter

Meaning red objects become more difficult to see at night than blue or green objects

116
Q

True or False?

Photoreceptors are evenly distributed across the retina

A

False

Photoreceptors are not evenly distributed across the retina

117
Q

Which part of the retina contains only cones?

A

Fovea

118
Q

What does Fovea contain?

A

Only cones

119
Q

True or False?

When looking directly at an object the image falls on the Choroid

A

False

When looking directly at an object the image falls on the fovea

120
Q

True or False?

Everywhere but the fovea contains more rods than cones

A

True

121
Q

True or False?

The fovea contains rods

A

False

The fovea contains cones

122
Q

Why are cones concentrated in the centre of our eye (the fovea)?

A

Because this is the centre of our field of view and the most effective location to have high spatial acuity and colour vision.

123
Q

True or False?

The blindspot has both rods and cones

A

False

The blindspot has neither rods nor cones

124
Q

When one neuron receives signals from many other neurons

This is known as…?

A

Neural convergence

125
Q

Which neuron receives signals from other neurons in neural convergence?

A

Ganglion cell receives signals from multiple photoreceptors

126
Q

Ganglion cell receives signals from multiple photoreceptors

This is known as…?

A

Neural convergence

127
Q

On average, how many rods send signals to 1 ganglion cell?

A

120 rods send signals to 1 ganglion cell

128
Q

On average, how many cones send signals to 1 ganglion cell?

A

6 cones send signals to 1 ganglion cell

129
Q

What determines visual acuity?

A

Neural convergence

130
Q

The ability to detect fine details of a stimulus is known as…?

A

Acuity

131
Q

Define acuity

A

The ability to detect fine details of a stimulus

132
Q

When you are able to detect fine details, you have…?

a. High acuity
b. Low acuity

A

a. High acuity

133
Q

When you are able to detect only course details, you have…?

a. High acuity
b. Low acuity

A

b. Low acuity

134
Q

Define low acuity

A

When you are able to detect only course details

135
Q

Define high acuity

A

When you are able to detect fine details

136
Q

Which photoreceptors have greater convergence?

a. Rods
b. Cones

A

a. Rods

137
Q

Which photoreceptors have less convergence?

a. Rods
b. Cones

A

b. Cones

138
Q

Less convergence = …………. acuity

a. Worse
b. Better

A

b. Better

139
Q

Which photoreceptors lead to lower acuity?

a. Rods
b. Cones

A

a. Rods

140
Q

Which photoreceptors lead to higher acuity?

a. Rods
b. Cones

A

b. Cones

141
Q

Why do rods lead to lower acuity?

A

Because they have greater convergence

Simply = Multiple rods have to share 1 ganglion cell to send their signals to (slower transmission)

Why = Because there are a lot of rods and not enough ganglion cells for each of the rods to send their signals to

142
Q

Why do cones lead to higher acuity?

A

Because they have fewer convergence

Simply = Each cone gets their own ganglion cell to send its signals to (faster transmission)

Why = Because there are not that many cones and there are sufficient ganglion cells for each of the cones to send their signals to

143
Q

Where in the eye do we have the highest acuity and why?

A

Fovea

Because it is concentrated with cones which have less convergence

144
Q

What is foveal acuity used for?

A

Used for scrutinizing highly detailed objects

145
Q

What is peripheral acuity used for?

A

Used for organizing the broad spatial scene and for seeing large objects

146
Q

Used for organizing the broad spatial scene and for seeing large objects

Is this foveal or peripheral acuity?

A

Peripheral

147
Q

Used for scrutinizing highly detailed objects

Is this foveal or peripheral acuity?

A

Foveal

148
Q

True or False?

Acuity decreases away from the fovea

A

True

149
Q

What ensures objects of interest are imaged on the fovea in fine detail (high acuity vision)?

A

Eye-movements

150
Q

Does acuity decrease in low-lighting or bright-lighting conditions?

A

Low lighting conditions

151
Q

Why does acuity decrease in low-lighting conditions?

A
  • Because cones (needed for high acuity due to less convergence) do not work in dim/dark light
  • Only rods work and rods have greater convergence which results in lower acuity
152
Q

Where is the retinal distribution of cones?

A

Fovea

153
Q

Where is the retinal distribution of rods?

A

Periphery

154
Q

How many types of cones are there?

A

3

155
Q

How many types of rods are there?

A

1

156
Q

Why is it harder to see colour at night?

A
  • Cones (photoreceptors that are responsible for colour vision) don’t work at night
  • We can only rely on rods which produce monochromatic vision
157
Q

Why is it easier to see stars in the night sky when we don’t look directly at them?

A
  • When you look at stars at night, it is a low amount of light being received by the eye
  • This amount of light is too little to stimulate the cones
  • But if you look directly at that star, the image of that star will fall on your fovea, where a lot of the cones are concentrated in
  • Fovea also does not contain any rods so if you look directly at the star, you can’t see it
  • But if you look at the star at a certain angle, you are now looking at it in a peripheral view where all the rods are located
158
Q

Why do we move our eyes to look directly at an object we’re interested in?

A
  • So that the image will land on the fovea
  • Fovea; allows us to use our cones for high acuity vision and colour vision
159
Q

Why is it hard to see anything when we go from bright sunlight into a dark room?

A
  • Bright light bleaches photopigment important for transduction
  • Photoreceptors lose sensitivity in bright light
  • When we go into darkness, we initially have poor sensitivity so we can’t see anything
  • But over time, photoreceptors will recover their sensitivity (dark adaptation)
160
Q

Why does everything look a bit blurry at night?

A
  • Cones (photoreceptors responsible for high acuity due to less convergence) do not work properly at night
  • We only use rods which result in low acuity due to more convergence

SEM 2 Sensation & Perception (12 decks)

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