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BS357: Introduction to Neuroscience I > Chapter 9: The Eye > Flashcards

Chapter 9: The Eye Flashcards

1
Q

the retina contains () that convert light energy into neural activity and detect the differences in intensity of light

A

photoreceptors

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2
Q

Axons of retinal neurons are bundled into ()

A

optic nerves

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3
Q

vision is primarily mediated by the ()

A

retina

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4
Q

First synaptic relay in the primary visual pathway; from here visual information ascends to cortex where it is interpreted and remembered

A

lateral geniculate nucleus (LGN)

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5
Q

Electromagnetic radiation that is visible to our eyes

A

Light

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6
Q

the distance between successive peaks

A

Wavelength

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7
Q

the number of waves per second

A

frequency

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8
Q

the difference between trough and peak

A

amplitude

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9
Q

Light Energy is proportional to ().

A

frequency

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10
Q

Short wavelength (high frequency): Gamma radiation, X-rays and (1) colors—(2) energy

A
  1. cool
  2. high
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11
Q

Longer wavelength (lower frequency): Radio waves and (1) colors—(2) energy

A
  1. hot
  2. low
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12
Q

Study of light rays and their interactions

A

Optics

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13
Q

Bouncing of light rays off a surface

A

Reflection

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14
Q

Transfer of light energy to a particle or surface

A

Absorption

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15
Q

Bending of light rays from one medium to another

A

Refraction

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16
Q

opening where light enters the eye

A

Pupil

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17
Q

() : white of the eye

A

Sclera

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18
Q

() : gives color to eyes

A

Iris

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19
Q

() : glassy transparent external surface of the eye

A

Cornea

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20
Q

(): bundle of axons from the retina

A

Optic nerve

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21
Q

small device (in eye clinics) that enable one to peer into the eye structure from pupil to retina

A

Ophthalmoscope

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22
Q

Blood vessels that originate from the () – where optic nerve connects to eye from brain -> Technically a blind spot

A

optic disk

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23
Q

()– place where light Is focused by cornea and lens; detects images that is sent to the brain -> not in peripheral vision

A

Macula

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24
Q

()– dark spot in the center of macula; Used as a reference point (to distinguish between nasal vs temporal retina)

A

Fovea

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25
Q

macular degeneration without bleeding

A

dry macular degeneration

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26
Q

macular degeneration with bleeding

A

wet macular degeneration

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27
Q

Cornea is the site of most of the () of the eyes

A

refractive power

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28
Q

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

A

Focal distance

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29
Q

() – refractive power of cornea

A

Diopters

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30
Q

Changing () provides extra focusing power.

A

shape of lens

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31
Q

Muscles around the lens make the lens flat ((1), for far objects) or fat ((2), for near objects)

A
  1. low refractive power
  2. high refractive power
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32
Q

Connections between retina and brain stem neurons that control muscles around pupil

A

pupillary light reflex

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33
Q

Pupil contributes to optical function by ()

A

continuously adjusting to different ambient light levels

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34
Q

the pupillary light reflex is (): shining a light into only one eye causes the constriction of the pupils of both eyes

A

Consensual

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35
Q

Pupil similar to the () of a camera

A

aperture

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36
Q

Amount of space viewed by retina when eye is fixated straight ahead

A

Visual field

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37
Q

ability to distinguish two nearby points; “resolution” of the eye

A

Visual acuity

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38
Q

direct (vertical) pathway of vision

A

photoreceptors -> bipolar cells -> ganglion cells

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39
Q

Retinal processing is also influenced by ()

A

lateral connections

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40
Q

Receive input from photoreceptors and project to other photoreceptors (laterally) and bipolar cells -> interaction between different fields of photoreceptors

A

Horizontal cells

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41
Q

Receive input from bipolar cells and project to ganglion cells, bipolar cells, and other amacrine cells; can also mediate and regulate the activity of neighboring photoreceptor signals during visual processing

A

Amacrine cells

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42
Q

The only light-sensitive cells in the retina are the ().

A

photoreceptors

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43
Q

The () are the only source of output from the retina and the only retinal neurons that fire an action potential.

A

ganglion cells

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44
Q

laminar organization of the retina: seemingly () layers

A

inside-out

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45
Q

Light passes through () before reaching photoreceptors.

A

ganglion cells and bipolar cells

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46
Q

outermost layer of retina: ()

A

retinal pigmental epithelium

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47
Q

() of the reitna: contains portion of photoreceptors embedded into RPE; major site of photoactivation

A

outer segment

48
Q

Bipolar, horizonal, amacrine cells are located laterally in () of the retina

A

upper layers

49
Q

retina’s Innermost layer: () -> project axons into forebrain

A

ganglionic cell layer

50
Q

Many nocturnal animals have reflective layer beneath photoreceptors, specifically RPE: (), which bounces light back at the photoreceptors.

A

tapetum lucidum

51
Q

nocturnal animals with tapetum lucidum are more sensitive to low light levels at the expense of ()

A

reduced acuity

52
Q

4 main regions of photoreceptor structure

A
  1. outer segment
  2. inner segment
  3. cell body
  4. synaptic terminal
53
Q

(1) of photoreceptors: a stack of membranous disks that absorb light, contains (2) -> trigger changes in membrane potential

A
  1. outer segment
  2. photopigment
54
Q

the cell body of a photoreceptor is found in the ()

A

inner segment

55
Q

types of photoreceptors

A

rods and cones

56
Q

photoreceptor with long, cylindrical outer segment with many disks

A

rods

57
Q

photoreceptors with shorter, tapering outer segment with fewer disks

A

cones

58
Q

(1) over 1000 times more sensitive to light than (2)

A
  1. rods
  2. cones
59
Q

Differences in rods and cones: “()”

A

duplex retina

60
Q

for organisms with duplex retina: at night, only (1) are active -> (2)

A
  1. rods
  2. scotopic
61
Q

for organisms with duplex retina: At intermediate light level: rods and cones are active ()

A

mesopic

62
Q

for organisms with duplex retina: Mostly (1) are active (2) at daytime

A
  1. cones
  2. photopic
63
Q

Rods are more sensitive because they have a lot more ()

A

photopigment

64
Q

Cones recognize (1)
Rods recognize (2) signals

A
  1. colors
  2. black and white
65
Q

in humans, there are (more/less) rods than cones

A

more

66
Q

Only the () are responsible for our ability to see color

A

cones

67
Q

():
Higher ratio of rods to cones and of photoreceptors to ganglion cells
More sensitive to low light, but less sensitive to color discrimination

A

peripheral retina

68
Q

Most of the cone cells are located in the (1), while most rod cells are in the (2)

A
  1. fovea
  2. peripheral retina
69
Q

in a (), there are no photoreceptors

A

blind spot

70
Q

In (1) retina, information from many photoreceptors is processed together; in (2) retina, 1:1 ratio of photoreceptor to ganglion cells

A
  1. periphery
  2. central
71
Q

cross-section of the fovea shows a pit in retina where outer layers are pushed aside -> maximizes ()

A

visual acuity

72
Q

central fovea has only () -> area of highest visual acuity

A

cones

73
Q

In peripheral fovea, light can be scattered -> less visual acuity because ()

A

light does not directly stimulate photoreceptors

74
Q

Phototransduction in rods is analogous to activity at () to cause a change in second messengers

A

G-protein-coupled neurotransmitter receptor

75
Q

phototransduction in rods starts when light energy interacts with ()

A

photopigment

76
Q

G protein is also involved in phototransduction; however the main difference is that in phototransduction, there is an (increase/decrease) in second messengers

A

decrease

77
Q

For phototransduction in particular, ion channel response is a decrease in ()

A

Na+ conductance

78
Q

the consequence of () in a photoreceptor is signal amplification—> allows us to have sensitivity to small amounts of light.

A

Light-activated biochemical cascade

79
Q

in dark status, G proteins in the Light-activated biochemical cascade are coupled with () -> keeps G protein inactivated

A

rhodopsin

80
Q

in a light status, G protein is activated due to conformational change in rhodopsin -> results in G protein being bound to ()

A

GTP

81
Q

in rod phototransduction, bound GTP stimulates the activity of () -> breaks down cGMP to GMP and results in decreased cGMP level -> closes cGMP-gated Na+ channel and hyperpolarizes membrane potential of rod cell

A

phosphodiesterase

82
Q

(): Rod outer segments are depolarized in the dark because of steady influx of Na+.

A

Dark current

83
Q

Photoreceptors (depolarize/hyperpolarize) in response to light.

A

hyperpolarize

84
Q

Types of photopigments in photoreceptors:
(1) – in rod cell
(2) – in cone cell

A
  1. Rhodopsin
  2. Opsin
85
Q

Inside photopigments is a chemical called (), which is derived from vitamin A and undergoes conformational change under light stimulation -> causes activation (disruption) of photopigment and alters MP

A

retinal

86
Q

Different opsins (correspond to different kinds of cone cells):

A
  1. Red (long wavelength)
  2. green (medium wavelength)
  3. blue (short wavelength)
87
Q

Mediated by contributions of blue, green, and red cones to retinal signal

A

color perception

88
Q

Mixing of red, green, and blue light causes () of the three types of cones -> perception of white

A

equal activation

89
Q

Opponent colors:

A

red-green
yellow-blue

90
Q

Opponent colors concept: Activation of red cones (activates/suppresses) activity of green cones and vice versa

A

suppresses

91
Q

() -> allow us to see objects in a dark room more clearly

A

dark adaptation

92
Q

factors in dark adaptation

A
  1. dilation of pupils
  2. regeneration of unbleached rhodopsin
  3. adjustment of functional circuitry
93
Q

explain how adjustment of functional circuitry occurs

A

Ganglion cells get more input from rod cells instead of cone cells

94
Q

Calcium’s role in light adaptation indirectly regulates levels of () -> regulation of ion channels

A

cGMP

95
Q

specifically, Ca2+ that enters the photoreceptors via Na+ channels inhibits () -> synthesizes cGMP

A

guanylyl cyclase

96
Q

closing of Na+ channels in photoreceptors decreases intracellular [Ca2+] -> activates guanylyl cyclase and ()

A

increases cGMP levels

97
Q

inhibition of guanylyl cyclase serves as () that exists even without light stimulation

A

basal stimulation

98
Q

when we move to a brighter environment, we are too sensitive to light -> Over time, MP is slowly () -> cells are able to respond to more light

A

depolarized and maintains a certain level

99
Q

Effect of pupil size is the (different/same) on all photoreceptors

A

same

100
Q

Area of retina where light changes neuron’s firing rate

A

receptive field

101
Q

the receptive field changes in ()

A

shape and stimulus specificity

102
Q

in a Receptive field: Stimulation in a small part of the visual field changes a cell’s ()

A

membrane potential.

103
Q

role of horizontal cells in antagonistic relationship of center-surround receptive fields

A

responsible for inverting the response in the surround

104
Q

ON bipolar cells have () receptors

A

metabotropic glutamate

105
Q

bipolar cells that are depolarized by light in receptive field center and hyperpolarized by light in receptive field surround

A

ON bipolar cells

106
Q

bipolar cells that are hyperpolarized by light in receptive field center and depolarized by light in receptive field surround

A

OFF bipolar cells

107
Q

OFF bipolar cells have () receptors

A

ionotropic glutamate

108
Q

Actual output from visual stimuli is interpreted as ()

A

ganglion cell response

109
Q

types of ganglion cells

A
  1. M-type (magno, large) -5%
  2. P-type (parvo, small) - 90%
  3. nonM-nonP type - 5%
110
Q

() is a specialized photopigment in ganglion cells -> can be stimulated by light directly -> direct depolarization

A

Melanopsin

111
Q

melanopsin is found in (), and is involved in controlling circadian rhythms via SCN (subcortical visual area)

A

Intrinsically photosensitive retinal ganglion cells (ipRGCs)

112
Q

different visual attributes are processed simultaneously using distinct pathways that are independent of each other

A

parallel processing

113
Q

Different receptive fields and response properties of retinal ganglion cells: detecting subtle contrast, low resolution

A

M cells

114
Q

Different receptive fields and response properties of retinal ganglion cells: small receptive field, discriminating fine details; red-green information

A

P cells

115
Q

Different receptive fields and response properties of retinal ganglion cells: blue-yellow information

A

nonM–nonP cells

BS357: Introduction to Neuroscience I (13 decks)

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