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PSY1016 Biological Psychology with Research Methods 1 > 6- The Retina > Flashcards

6- The Retina Flashcards

1
Q

Where is the retina?

A

At the back of the eye

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2
Q

How many cells are in the retina?

A

100 million+

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3
Q

How does light reach photoreceptors in the retina?

A

Light passes through overlying tissue

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4
Q

What is the advantage of the inside-out arrangement in the retina?

A

Pigmented epithelium below photoreceptors absorbs light that passes entirely through the retina that minimises light scattering

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5
Q

What do photoreceptors do?

A

Convert electromagnetic radiation to neural signals

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6
Q

What are the two types of photoreceptors?

A

Cones and rods

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7
Q

What are the 3 main regions of photoreceptors?

A

Outer segment, inner segment, synaptic terminal

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8
Q

Where is there a higher ratio of rods to cones?

A

In the peripheral retina

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9
Q

Why are rods more sensitive to light?

A

There is a higher ratio of photoreceptors to ganglion cells

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10
Q

Where is the only place cones are found and why?

A

At the fovea as they have a high acuity and low sensitivity

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11
Q

Why is there more convergence in the rod system?

A

Increasing sensitivity while decreasing acuity

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12
Q

What is phototransduction?

A

The conversion of light to neural signals

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13
Q

What do rods and cones contain?

A

Photosensitive pigment

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14
Q

What does the absorption of photons of light by pigment generate?

A

Electrical signal

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15
Q

What does the G protein-linked receptor respond to?

A

Light rather than neurotransmitters

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16
Q

What happens to Na+ channels in the dark?

A

They partially open

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17
Q

What happens to Na+ channels in the light?

A

They close and rods hyperpolarise

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18
Q

How do the 3 different pigments in cones differ?

A

Wavelengths and spectral sensitivity

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19
Q

How do we perceive colour?

A

Through visible light in the electromagnetic spectrum

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20
Q

What is ability to perceive light dependent on?

A

The information we are given

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21
Q

What are the 3 different types of cones in humans?

A

Red, blue, green

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22
Q

Vision in cones

A

Photopic (daytime) and colour vision

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23
Q

Main location of cones

A

Fovea

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24
Q

Why do cones have high acuity?

A

1 cone to 1 ganglion cell

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25
Q

Vision in rods

A

Scotopic (night time) and noncolour

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26
Q

Main location of rods

A

Periphery

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27
Q

Why do rods have low acuity?

A

Many rods to 1 ganglion cell

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28
Q

What cells in the retina fire action potentials?

A

Ganglion cells

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29
Q

How do other cells in the retina respond to stimulation?

A

With graded changes in membrane potential

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30
Q

What is the direct pathway of ganglion cells to fire action potentials?

A

Photoreceptor –> bipolar cell –> ganglion cell

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31
Q

What happens after light hyperpolarises photoreceptor cells?

A

They stop releasing glutamate to bipolar cells, which depolarise and release neurotransmitters to ganglion cells

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32
Q

How is the visual field mapped?

A

Point-to-point on the retina

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33
Q

What lateral connections in the retina modify responses?

A

Connections of horizontal and amacrine cells

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34
Q

100 million receptors are recoded to how many ganglion cells?

A

1.25 million

35
Q

What does each receptive field for each ganglion cell do?

A

Combines input from a number of photoreceptors

36
Q

When do cells in centre-surround receptive fields respond best?

A

When there’s contrast

37
Q

2 types of retinal ganglion cells

A

M-type and P-type

38
Q

What are the 3 differences between types of retinal ganglion cells?

A

Appearance
Connectivity
Electrophysiological response properties

39
Q

Where is input to M-type cells primarily from?

A

Rods

40
Q

Where is input to P-type cells primarily from?

A

Cones

41
Q

What information does the retina extract?

A

About differences in brightness/contrast and colour

42
Q

What is included in retinofugal projection? (7)

A
  • Optic nerve
  • Optic chiasm
  • Lateral geniculate nuclei
  • Optic radiation
  • Primary visual cortex
  • Hypothalamus (nonthalamic)
  • Superior colliculus (nonthalamic)
43
Q

Role of the hypothalamus in retinofugal projection

A

Biological rhythms control, including sleep and wakefulness

44
Q

Role of the superior colliculus in retinofugal projection

A

Orients eye in response to new stimuli

45
Q

What is contralateral wiring?

A

Left hemifield projects to right side of brain and vice versa

46
Q

Which axons cross and which stay ipsilateral?

A

Ganglion cell axons from nasal retina cross
Temporal retinal axons stay ipsilateral

47
Q

Where does information cross?

A

At the optic chiasm

48
Q

What would a lesion in a visual hemifield mean?

A

We lose parts of the visual field

49
Q

What would a lesion to the optic tract mean?

A

We would lose information on a contralateral hemifield

50
Q

What type of structure is the lateral geniculate nucleus?

A

Thalamic

51
Q

What is the first synaptic relay in the primary visual pathway?

A

Lateral geniculate nucleus

52
Q

What is monocular input?

A

Input from two eyes is kept separate

53
Q

What are receptive fields of the lateral geniculate nucleus similar to?

A

Ganglion cells

54
Q

What are neighbouring regions of the visual field processed by?

A

By neighbouring regions of the visual cortex

55
Q

What areas is more of the cortex devoted to?

A

Areas of high acuity

56
Q

How is the retina stimulated?

A

By a point of light

57
Q

Where is the peak of the broad distribution of activity in the striate cortex?

A

At the corresponding retinotopic location

58
Q

How are cells with same eye preferences grouped?

A

Into ocular dominance columns

59
Q

What do cells within the same column share?

A

The same ocular dominance and receptive fields in similar areas of the visual field

60
Q

What is the receptive field of a cortical visual neuron?

A

The area of a visual field within which it is possible for a visual stimulus to influence firing of a given neuron

61
Q

What is orientation selectivity?

A

Cells respond to particular orientation

62
Q

What is direction selectivity?

A

Cells respond to direction of movement

63
Q

What is an orientation column?

A

Orientation of nearby neurons is related

64
Q

What is a cortical module?

A

Each module that is capable of analysing every aspect of portion of the visual field

65
Q

What do ocular dominance columns respond to?

A

Respond more to information from 1 eye

66
Q

3 things caused by damage to the primary visual cortex

A

Scotomas, completion, and blinsight

67
Q

What is a scotoma?

A

An area of blindness in the contralateral visual field due to damage to the primary visual cortex

68
Q

What is blindsight?

A

A response to visual stimuli outside conscious awareness of ‘seeing’

69
Q

4 aspects of functional areas of the secondary and association visual cortex

A
  • Neurons in each area respond to different visual cues
  • Lesions result in specific deficits
  • Anatomically distinct
  • Retinotopically organised
70
Q

What analysis is involved in the dorsal stream?

A

Analysis of visual motion and visual control of action

71
Q

Where is area MT?

A

In the temporal lobe

72
Q

How is the dorsal stream arranged?

A

Into direction-of-motion columns

73
Q

What is akinetopsia?

A

Motion blindness

74
Q

How is akinetopsia caused?

A

Damage to middle temporal area of cortex

75
Q

What deficiency is implicated in akinetopsia?

A

Deficiency in ability to see movement progress in normal smooth fashion

76
Q

What perception does the ventral stream control?

A

Perception of the visual world and recognition of objects

77
Q

What does the area V4 control?

A

Colour vision and shape perception

78
Q

What does damage to area V4 cause?

A

Achromatopsia- partial or complete loss of colour vision

79
Q

What does damage to the fusiform gyrus (face area) cause?

A

Prosopagnosia- inability to distinguish faces

80
Q

What is visual perception?

A

Identifying and assigning meaning to objects

81
Q

What are retinal ganglion cells sensitive to?

A

Contrast and wavelength of light

82
Q

What is involved in the striate cortex?

A

Orientation and direction selectivity, binocularity

83
Q

What response does the extrastriate cortical areas control?

A

Selective responses to complex shapes

PSY1016 Biological Psychology with Research Methods 1 (34 decks)

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