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Neurobiology > Lecture 6 > Flashcards

Lecture 6 Flashcards

1
Q

outer layer of eye composed of white, fibrous tissue

A

sclera

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2
Q

transparent front part of eye that controls 80% of the focusing power

A

cornea

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3
Q

What are the outer structures of the eye?

A

sclera

cornea

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4
Q

What are the middle structures of the eye?

A

iris
pupil
ciliary body

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5
Q

colored portion of eye; contains muscles that adjust pupil size

A

iris

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6
Q

open during dim light, closed during bright light

A

pupil

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7
Q

ring of tissue that circles the lens; made of muscle and vasculature

A

ciliary body

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8
Q

What are the internal structures of the eye?

A

retina
lens
aqueous humor
vitreous humor

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9
Q

part of the eye that detects light, processes information, and sends it to the brain

A

retina

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10
Q

changes shape to allow fine focus

A

lens

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11
Q

provides nutrients to anterior eye

A

aqueous humor

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12
Q

provides shape, contains macrophages that remove debris

A

vitreous humor

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13
Q

contraction of lens by ciliary muscle

A

focus

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14
Q

Each eye sees ___ degrees of arc in a horizontal plane, __ degrees nasally and __ degrees temporally.

A

150
50
100

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15
Q

What is the role of the retina?

A

converts light energy into action potentials

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16
Q

What are the 5 types of neurons found in the retina?

A 
photo receptors
biopolar cells
ganglion cells
horizontal cells
amacrine cells
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17
Q

What is the basic unit of transmission in the retina?

A

photoreceptor > bipolar cell > ganglion

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18
Q

make up to outer nuclear layer of the retina

A

photorecepters (rods and cones)

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19
Q

make up the inner nuclear layer of the retina

A

interneurons (horizontal, bipolar, amacrine cells)

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20
Q

make up the ganglion cell layer of the retina

A

output neurons (retinal ganglion cells)

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21
Q

The plexiform layers of the retina contain ____.

A

synaptic connections

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22
Q

made up of axons that carry optic information to the brain

A

optic nerve

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23
Q

The photoreceptors are located at the ___ of the retina.

A

back

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24
Q

What are the two light receptors in the retina and what kind off light do they detect?

A

rods - low light

cones - bright light

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25
Q

Photoreceptors absorb light and then transduce to ___ than ____ signals in the outer segment. Then the signals transduce again to ___ signals in the synaptic terminal.

A

chemical
electrical
chemical

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26
Q

There are no ____ in the photoreceptors. Projections are ___. Light causes ____ that leads to ___ transmitter release.

A

action potentials
short
hyperpolarization
less

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27
Q

What is rhodopsin?

A

a GPCR found in the rods of the retina; extremely sensitive to light (good for low light)

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28
Q

Conversion of ____ in rhodopsin to _____ via a photon of light causes activation of ____ (light to chemical signal). Then, the ___ dissociates from ___ and ____ recycles to ___.

A 
11-cis-retinal
all trans retinal
opsin
retinal
opsin
trans-retinal
11-cis-retinal
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29
Q

vitamin A found in carrots

A

retinal

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30
Q

Activated rhodopsin activates a ____, which activates ____. That breaks down ___, which opens a cation channel for __ and __ in the photoreceptor outer segment. This ___ the cell. Light depletes ___, which closes the channel and ___ the cell.

A 
G protein
phosphodiesterase
cGMP
Na+
Ca+2
depolarizes
cGMP
hyperpolarizes
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31
Q

What is light’s role in rhodopsin activation?

A
  • reduces sodium current through cGMP gated channels
  • hyperpolarizes cell
  • reduces vesicle release
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32
Q

Each activated rhodopsin can activate 100s of ____, each of which can activate many molecules of ____, each of which can hydrolyze 1000s of molecules of ____. One photon of light closes about ___ ion channels per second.

A

g proteins
phosphodiesterase
cGMP
200

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33
Q

What is the unique feature of rods?

A

detect a single photon of light, but black and white only (night vision)

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34
Q

What is a unique feature of cones?

A

can detect ~100 photons (less sensitive than rods), but can detect colors

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35
Q

night vision; active rods, light too dim for cones

A

scotopic

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36
Q

color vision; cones active, rods bleached (inactive)

A

photopic

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37
Q

How long does light adaptation take? What about dark adaptation? What accounts for the difference?

A

light: occurs quickly
dark: up to ~25 min
Rhodopsin is bleached in bright light and needs to regenerate

38
Q

What are the 3 color-specific cones?

A

red (long wavelength))
green (medium wavelength)
blue (short wavelength)

39
Q

What causes color blindness?

A

mutations in cone opsins

40
Q

In which cones are mutations most common?

A

red or green opsins

41
Q

Colorblind people have normal ____ because rods are more sensitive than cones.

A

light sensitivity

42
Q

red-green colorblindness; long-wavelength cone affected (red)

A

protanopia

43
Q

red-green colorblindness; medium wavelength cone affected (green)

A

deuteranopia

44
Q

a rare condition in which the individual only has one working type of cone

A

total color blindness (monochromacy)

45
Q

Colorblindness is often inherited: ____ and ___. About __% males and __% females will inherit it.

A

x-linked
recessive
8
0.4

46
Q

The human retina has ____ rods and ____ cones.

A

91 million

4.5 million cones

47
Q

central retina where cones are highly packed; absolute center is completely rod-free

A

fovea

48
Q

There is high ___ in the fovea and greater ____ in the periphery.

A

visual acuity

light sensitivity

49
Q

In the fovea, other cell layers are displaced. Why?

A

it allows light to hit cones with less interference

50
Q

There are two types of bipolar cells. ON cells ___ with light while OFF cells ____ with light.

A

depolarize

hyperpolarize

51
Q

In the dark, there is ___ glutamate release by the photoreceptor. OFF bipolar cells express ____ which is ___. They ____ from glutamate and ___ in firing in response to light. ON bipolar cells express ____ which is ____. They ____ from glutamate and ____ firing in response to light.

A 
AMPA
inotropic
depolarize
decrease
mGluR
metabotropic
hyperpolarize
increase
52
Q

In the light, there is ___ glutamate release by the photoreceptor. OFF bipolar cells express ____ which is ___. They ____ from glutamate and ___ in firing in response to light. ON bipolar cells express ____ which is ____. They ____ from glutamate.

A 
low
AMPA
ionotropic 
depolarize
decrease
mGluR
metabotropic
hyperpolarize
increase
53
Q

In the dark, OFF bipolar cells are ____ and ON bipolar cells are ____. In the light, OFF bipolar cells are ____ and ON bipolar cells are ____. In light, ON bipolar cells ___ the signal.

A 
active
inactive
inactive
active
invert
54
Q

Retinal ____ send APs to the brain and detect ____.

A

ganglion cells

light intensity

55
Q

the area to which a particular RGC is responsive

A

receptive field

56
Q

Receptive fields have ___ and ___ portions. ON-center ganglion cells ___ when light goes on. OFF-center ganglion cells ___ when light goes on.

A

center
surround
depolarize
hyperpolarize

57
Q

What is a post-inhibitory rebound?

A

stimulation of nerve impulses after hyperpolarization

58
Q

In the direct pathway of information processing in the retina, the bipolar cells connect ____.

A

directly to ganglion cells

59
Q

In the indirect pathway of information processing in the retina, the bipolar cells connect ____.

A

to horizontal and machine cells which make lateral connections to the ganglion cells

60
Q

In an ON center ganglion, a small spot of light leads to ___, while a large spot of light leads to ___. In summary, these ganglion cells respond better to ___ and high ___.

A

no inhibition
inhibition
well aimed small spots
contrast

61
Q

In an OFF center RGC, dark light in the center leads to _____.

A

depolarization

62
Q

Center-surround organization enhances sensitivity to ___ and ___.

A

edges

contrast

63
Q

RGCs fire depending on ___ not absolute ____.

A

contrast

light intensity

64
Q

Our visual system does not encode ____.

A

light intensity

65
Q

streams of information related to different visual properties are dealt with simultaneously by different circuits

A

parallel processing

66
Q

Receptive field properties get extracted as signal moves from photoreceptors to RGCs to brain and only ____ is transmitted.

A

relevant information

67
Q

2 dimensional surface of the retina is mapped (topographically arranged) onto the surface of subsequent structures

A

retinotopy

68
Q

All RGC axons exit the eye

at the ____ (blind spot) and form a large, myelinated nerve called the ___.

A

optic disk

optic nerve

69
Q

point where optic nerve enters the brain

A

optic chiasm

70
Q

The L visual field from ____ projects to R cortical hemisphere and vice versa.

A

both eyes

71
Q

After chiasm, projections are called ____. These projections contain ____ and ____ RGC axons. They project to ___ of the dorsolateral thalamus and carry information about left visual field to ____ LGN and vice versa.

A 
optic tracts
ipsilateral temporal
contralateral nasal
lateral geniculate nucleus (LGN)
right
72
Q

The right LGN projects to ___ in ___ of the cerebral cortex.

A

right visual cortex

occipital lobe

73
Q

Each LGN layer is eye-specific: ipsilateral eye projects to layers ___ and contralateral eye projects to layers ___.

A

2, 3, 5

1, 4, 6

74
Q

Layers 1, 2 in the LGN are ___ (detect ___); receive input from ganglion cells that detect gross ___ and ____.

A

magnocellular
motion
shape
movement

75
Q

Layers 3-6 are ___ (small cells, detect ___); receive input from ganglion cells that detect ___.

A

parvocellular
shape
shape

76
Q

All layers of the LGN; detect color

A

koniocellular

77
Q

___ RGCs innervate each LGN neuron and the visual receptive fields in LGN are almost ___ to those in retina.

A

1-2

identical

78
Q

Magnocellular layers have a ___ center surround and detect ___ bursts and are ___ to color.

A

large
transient
insensitive

79
Q

Parvocellular layers have a ___ center surround and detect ___ bursts and are ___ to color.

A

small
sustained
sensitive

80
Q

In the occipital lobe, the upper visual field is represented ___ the calcarine sulcus, the lower field ___.

A

below

above

81
Q

Fovea is represented on a huge amount of cortex because of its ___ and ___.

A

high sensitivity

density of cones

82
Q

The visual cortex has _ layers, each with specific inputs and outputs. The LGN projects to layer _, output is layer 5. The largest input is to __ (magnocellular and most parvocellular)

A

6
4
5
4C

83
Q

allow for segregation of visual input from each eye

A

ocular dominance columns

84
Q

Axons from L and R eye are ____ in layer 4.

A

segregated

85
Q

What happens during monocular depravation (i.e., close one eye) during development?

A

lose ocular dominance columns

86
Q

Neurons in V1 respond strongly to a bar of light at a particular orientation and less strongly or not at all to other orientations. Why is this?

A

convergence of several center surround cells –> orientation sensitivity

87
Q

Some cells in V1 are also ___ selective; respond strongly to lines/bars/edges moving in a ___ but not at all in the ____.

A

direction
preferred direction
opposite direction

88
Q

Depth perception requires ___, ___ vision. Its based on the ___ of each visual field in a binocular cortical neuron. Some cortical neurons respond to visual objects ___ than the plane of focus, others ___ the plane of focus.

A 
binocular
aligned
disparity of the position
closer
beyond
89
Q

What are the binocular cues?

A

convergence

binocular disparity

90
Q

What are the monocular cues?

A 
linear perspective relative
size/height
shading
aerial perspective
texture

Neurobiology (9 decks)

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