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EXCI360 > Lecture 4: Visual Systems > Flashcards

Lecture 4: Visual Systems Flashcards

1
Q

Retina:

A

the innermost layer of
the eye.

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2
Q

The retina is considered a part of:

A

The Nervous System.

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3
Q

The retina contains:

A

neurons that are
sensitive to light and convert
visual information to electrical
signal and transmit it to the
brain.

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4
Q

Photosensitive
(photoreceptor) neurons (2):

A

Rods
Cones

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5
Q

Rod shape:

A

rod-shaped (rectangular
head)

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6
Q

rod number:

A

120 millions

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7
Q

Rod location in the retina:

A

Periphery

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8
Q

Rod luminosity level

A

Dim light (high
sensitivity to light) –
Night vision

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9
Q

rod vision accuracy

A

Low resolution

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10
Q

Rod: Photosensitive pigments:

A

Rhodopsin (found in
carrots)

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11
Q

Rod: Type of cell:

A

1 type: monochromic
(absorb white color)

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12
Q

Rod : Color Vision?

A

No

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13
Q

Cone shape:

A

Cone-shaped (triangular
head)

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14
Q

Cones number:

A

8 millions

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15
Q

Cones: Location in the Retina:

A

Center (fovea)

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16
Q

Cones: Luminosity level:

A

Bright light (low
sensitivity to light) –
Day vision.

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17
Q

Cones: Vision Accuracy:

A

High resolution

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18
Q

Cones: Photosensitive pigments:

A
  • Iodopsin
  • Porphyropsin
  • Cyanopsin
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19
Q

Cones: Type of cell:

A

3 types:
➢ S-cones (absorb blue)
➢ M-cones (absorb green)
➢ L-cones (absorb red)

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20
Q

Cones: Color vision:

A

yes

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21
Q

S-Cones absorb:

A

blue

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22
Q

M-Cones absorb:

A

green

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23
Q

L-cones absorb:

A

red

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24
Q

At the lowest levels of illumination, only __ are activated (high
sensitivity to light).

A

rods

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25
Q

__ begin to contribute to light perception at about the level of
__ (i.e. mesopic vision)

A

Rods,Starlight

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26
Q

are the only receptors that function under relatively
bright light spectrum (phototopic vision) (e.g. indoor lighting, sunlight).

A

Cones

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27
Q

5 Classes of Neurons:

A
  1. Photosensitive Cells (Rods + Cones)
  2. Bipolar Cells
  3. Ganglion Cells
  4. Horizontal Cells
  5. Amacrine cells
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28
Q

Bipolar cells connect:

A

photosensitive
cells to ganglion cells.

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29
Q

Ganglion cells:

A

Axons form optic nerve

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30
Q

Horizontal cells:

A

Regulate the activity of
photosensitive cells.

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31
Q

Amacrine cells:

A

Allow Lateral
communication between
neurons.

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32
Q

In dark (absence of light), rods/cones are :

A

Depolarized
Na+ & Ca2+ channels are open, allowing Na+ & Ca2+ enter to the cell
and depolarize it.

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33
Q

When stimulated by light, rods/cones are

A

hyperpolarized

Na+ & Ca+ channels are closed and K+ channels are open =
hyperpolarization.

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34
Q

In Dark (not stimulated by light):

A

➢ Rods/Cones are depolarized.
➢ Rods/Cones inhibit (block) Bipolar cells (hyperpolarized)
➢ Bipolar cells can not excite Ganglion cells (hyperpolarized)
➢ Visual information is not transmitted to CNS.

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35
Q

In Light (stimulated by light):

A

➢ Rods/Cones are hyperpolarized.
➢ Bipolar cells released from rods/cones inhibition
(depolarized),
➢ Bipolar Cell excite Ganglion cells (depolarized)
➢ Visual information is transmitted to CNS

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36
Q

Ganglion cells respond differently
to

A

light and dark depending on the
location of light/dark in the visual
field (center vs periphery)

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37
Q

Two classes of ganglion cells:

A

On-center cells
Off-center” cells

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38
Q

“On-center” cells:

A

active to light
spot in center of the visual field
and silent to dark spot in center.

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39
Q

“Off-center” cells:

A

silent to light
spot in center of the visual field
and active to dark spot in center.

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40
Q

The activity of On-center/Off-center
ganglion cells is controlled by

A

multiple
interactions between the
photosensitive cells, bipolar cells and
horizontal cells.

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41
Q

specific response to light
constitutes an efficient manner to

A

transmit visual information to the brain
(i.e. encoding visual information).

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42
Q

On the retinal surface, the image is

A

inverted top to bottom and reversed
right to left.

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43
Q

On the retinal surface, the image is inverted top to bottom and reversed
right to left.
The image is converted to it real position in

A

the visual cortex

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44
Q

Visual Field:

A

part of word seen by the eye

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45
Q

Visual Field: part of word seen by the eye:
Divided to 2 fields:

A

Left & Right

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46
Q

Divided to 2 fields: Left & Right
➢ Each field is divided to

A

Median hemi-field & Lateral hemi-field

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47
Q

Median hemi-fields : seen by the

A

Temporal retina.

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48
Q

Lateral hemi-fields seen by the

A

Nasal retina.

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49
Q

Visual fields of both eyes overlap in the central portion =

A

Binocular visual field.

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50
Q

Axons of the ganglion cells form

A

optic nerve (3rd
order neuron).

51
Q

60% of the optic nerve fibres crosse (decussate) at
the __ to the opposite side of the brain (contralateral)

A

optic chiasm

52
Q

40% of the fibres stay on

A

the same
side (ipsilateral) of the brain

53
Q

Fibres from the nasal retina project to

A

the contralateral side of the brain (i.e. crosse at the
optic chiasm).

54
Q

Fibres from the temporal retina project to

A

the
ipsilateral side (do not crosse).

55
Q

After the optic chiasm, the optic fibres form the

A

tract

56
Q

The majority of optic fibres terminate in the

A

Lateral
Geniculate Body (LGB) in the thalamus.

57
Q

Neurons from the LGB form the

A

optic radiation (4th
order neuron) and terminate in the visual cortex
(occipital lobe).

58
Q

Axons of the ganglion cells project also
to other midbrain areas (3):

A

(1) Pretectum
(2) Hypothalamus
(3) Superior colliculus

59
Q

Pretectum:

A

Control of the pupillary light
reflex.

60
Q

Hypothalamus:

A

Regulation of circadian
rhythms (biological clock).

61
Q

Superior colliculus:

A

orienting the
movements of head and eyes (see the
vestibular system).

62
Q

Circuitry responsible for the pupillary light reflex (4 steps):

A
  1. Optic nerves from both eyes project to the pretectum to control the pupillary light reflex
  2. Pretectum neurons project to the Edinger-Westphal nucleus
  3. Edinger-Westphal neurons send their axons via the oculomotor nerve to terminate on the
    ciliary ganglion neurons
  4. The ciliary ganglion neurons (parasympathetic) innervate the constrictor muscle in the iris
    and cause iris muscle to adjust the size of the pupil.
63
Q

What are other names for the visual cortex?

A

= striate cortex = primary visual cortex = V1 = Brodmann’s area 17.

64
Q

Visual cortex processes

A

the basic of sensory information sent by the retina (e.g. place back
the inverted image to its original position, binocular vision, 3D image, ect).

65
Q

Each region of the retina projects to

A

a dedicated region of the visual cortex (i.e. map of
sensory representation).

66
Q

macula
fovea

A

central region of the retina

67
Q

Sensory information from the central region of the retina (macula,
fovea) have

A

a large representation in the visual cortex.

68
Q

he central region of the retina sends
the large portion of sensory information to

A

the visual cortex (binocular vision, HD vision)

69
Q

There are __ cellular layers in the visual cortex “Cytoarchitecture”.

A

6

70
Q

In the visual cortex, layer __ is the main input ( receives LGN fibers)

A

Layer 4

71
Q

Layers 5 and 6 in the primary visual (striate) cortex are

A

descending outputs (i.e. outputs to sub-cortical regions).

72
Q

Layers 2 and 3 in the primary visual (striate) cortex are:

A

ascending outputs (i.e. outputs to other cortical regions)

73
Q

The lateral geniculate nucleus (LGN)
receives input from

A

both eyes

74
Q

Geniculate
neurons are

A

monocular (i.e. receive the
images of each eye separately).

75
Q

LGN fibres project to

A

layer 4 of the striate
cortex.

76
Q

LGN inputs are segregated in layer 4 in

A

ocular dominance columns

77
Q

The neurons of layer 4 are:

A

monocular

78
Q

Layer 4 neurons send their outputs to
other cortical layers; it is at this stage
where:

A

the images from both eyes
converges to form one single image
(cyclopean representation of the external
world = binocular vision).

79
Q

Neurons in the primary visual cortex respond selectively to

A

oriented edges

80
Q

Different neuron types respond selectively to

A

different visual information (i.e.
edge orientation, shape, color, …).

81
Q

Primary visual cortex projects to

A

other cortical areas “Extrastriate cortex’’ (secondary visual
cortex) involved in complex visual perception:

82
Q

Dorsal pathway is the __ pathway

A

where/action pathway

83
Q

dorsal pathway projects to:

A

the parietal lobe

84
Q

The dorsal pathway is responsible for :

A

Spatial aspect of vision (e.g. analysis of motion, positional relationship between objects, etc)

85
Q

The ventral pathway is the __ pathway

A

what pathway, perception

86
Q

ventral pathway projects to:

A

The temporal lobe

87
Q

The ventral pathway is responsible for:

A

object recognition

88
Q

The eye is a fluid-filled sphere enclosed by:

A

3
layers of tissue:

89
Q

The eye is a fluid-filled sphere enclosed by 3
layers of tissue, the sclera is the __ layer

A

outermost

90
Q

The eye is a fluid-filled sphere enclosed by 3
layers of tissue, the choroid is the __ layer

A

intermediate

91
Q

The eye is a fluid-filled sphere enclosed by 3
layers of tissue, the retina is the __ layer

A

innermost

92
Q

The eye has two fluid compartments:

A

(1) Aqueous humour
(2) Vitreous humour

93
Q

aqueous humour can be found in:

A

The anterior chamber

94
Q

Aqueous humour in the anterior chamber is a:

A

Watery liquid that supplies nutriments to surrounding
structures.

95
Q

Vitreous humour is a thick or thin fluid?

A

thick gelatinous

96
Q

Vitreous humor, a thick gelatinous that fills the
space of

A

posterior chamber (i.e. between the back
of the lens and the retina)

97
Q

What is the function of the vitreous humour?

A

It maintains the shape
of the eye and supplies nutriments to surrounding
structures.

98
Q

What is the function of the lens in the eye

A

refracts (bends) light rays

99
Q

Sclera:

A

white fibrous tissue
forming the outermost layer
of the eye.

100
Q

At the front of the eye, Sclera becomes the __

A

Cornea

101
Q

Cornea:

A

transparent tissue that
separates and protects the
eye from the external
environment and allows light
rays into the eye.

102
Q

Choroid:

A

Intermediate layer. Is a
capillary bed that nourishes the
retinal cells.

103
Q

Ciliary body:

A

a ring of tissue that
encircles the lens and consists of
a muscular and vascular part:

104
Q

Ciliary muscle controls

A

the
shape of the lens

105
Q

cilliary muscles connected to the lens by:

A

the Zonule fibers.

106
Q

Ciliary processes produces

A

the aqueous humor in the
anterior chamber.

107
Q

Iris:

A

coloured portion of the eye
seen through the cornea, contains
2 sets of muscles that contract and
adjust the size of the pupil.

108
Q

Function of the lens:

A

refracts (bends)
light rays coming into the
eye and generates a
focused image on the
surface of the retina.

109
Q

Accommodation

A

dynamic
changes in the refractive power of
the lens to form a shape image on
the retina

110
Q

Accomodation changes are made by:

A

the contraction of the
Ciliary muscle.

111
Q

Distant vision: lens becomes

A

thin
and flat

112
Q

Distant vision: __ refractive power

A

LESS

113
Q

Near vision: lens becomes:

A

thick
and round

114
Q

near vision: __ refractive power

A

most

115
Q

Emmetropia:

A

In the normal eye,
the lens has a right accommodation
level, the image is focused right on
the retina

116
Q

Myopia:

A

he lens over
accommodates (i.e. high
refractive power),

117
Q

In myopia, the image is focused

A

in front of the retina

118
Q

in myopia, it is hard to see:

A

distant objects

119
Q

myopia is corrected by __ eye glasses

A

myopia is corrected by concave (diverging) eye glasses

120
Q

Hyperopia: the lens __

A

does not
accommodate enough (i.e. weak
refractive power)

121
Q

In hyperopia, the image is focused:

A

beyond the retina

122
Q

Hyperopia makes it hard to see:

A

nearby objects

123
Q

Hyperopia is corrected by:

A

convex (converging) eye glasses

EXCI360 (5 decks)

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