Lecture 6 Flashcards
(90 cards)
1
Q
outer layer of eye composed of white, fibrous tissue
A
sclera
2
Q
transparent front part of eye that controls 80% of the focusing power
A
cornea
3
Q
What are the outer structures of the eye?
A
sclera
cornea
4
Q
What are the middle structures of the eye?
A
iris
pupil
ciliary body
5
Q
colored portion of eye; contains muscles that adjust pupil size
A
iris
6
Q
open during dim light, closed during bright light
A
pupil
7
Q
ring of tissue that circles the lens; made of muscle and vasculature
A
ciliary body
8
Q
What are the internal structures of the eye?
A
retina
lens
aqueous humor
vitreous humor
9
Q
part of the eye that detects light, processes information, and sends it to the brain
A
retina
10
Q
changes shape to allow fine focus
A
lens
11
Q
provides nutrients to anterior eye
A
aqueous humor
12
Q
provides shape, contains macrophages that remove debris
A
vitreous humor
13
Q
contraction of lens by ciliary muscle
A
focus
14
Q
Each eye sees ___ degrees of arc in a horizontal plane, __ degrees nasally and __ degrees temporally.
A
150
50
100
15
Q
What is the role of the retina?
A
converts light energy into action potentials
16
Q
What are the 5 types of neurons found in the retina?
A
photo receptors biopolar cells ganglion cells horizontal cells amacrine cells
17
Q
What is the basic unit of transmission in the retina?
A
photoreceptor > bipolar cell > ganglion
18
Q
make up to outer nuclear layer of the retina
A
photorecepters (rods and cones)
19
Q
make up the inner nuclear layer of the retina
A
interneurons (horizontal, bipolar, amacrine cells)
20
Q
make up the ganglion cell layer of the retina
A
output neurons (retinal ganglion cells)
21
Q
The plexiform layers of the retina contain ____.
A
synaptic connections
22
Q
made up of axons that carry optic information to the brain
A
optic nerve
23
Q
The photoreceptors are located at the ___ of the retina.
A
back
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
25
Photoreceptors absorb light and then transduce to ___ than ____ signals in the outer segment. Then the signals transduce again to ___ signals in the synaptic terminal.
chemical
electrical
chemical
26
There are no ____ in the photoreceptors. Projections are ___. Light causes ____ that leads to ___ transmitter release.
action potentials
short
hyperpolarization
less
27
What is rhodopsin?
a GPCR found in the rods of the retina; extremely sensitive to light (good for low light)
28
Conversion of ____ in rhodopsin to _____ via a photon of light causes activation of ____ (light to chemical signal). Then, the ___ dissociates from ___ and ____ recycles to ___.
```
11-cis-retinal
all trans retinal
opsin
retinal
opsin
trans-retinal
11-cis-retinal
```
29
vitamin A found in carrots
retinal
30
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.
```
G protein
phosphodiesterase
cGMP
Na+
Ca+2
depolarizes
cGMP
hyperpolarizes
```
31
What is light's role in rhodopsin activation?
- reduces sodium current through cGMP gated channels
- hyperpolarizes cell
- reduces vesicle release
32
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.
g proteins
phosphodiesterase
cGMP
200
33
What is the unique feature of rods?
detect a single photon of light, but black and white only (night vision)
34
What is a unique feature of cones?
can detect ~100 photons (less sensitive than rods), but can detect colors
35
night vision; active rods, light too dim for cones
scotopic
36
color vision; cones active, rods bleached (inactive)
photopic
37
How long does light adaptation take? What about dark adaptation? What accounts for the difference?
light: occurs quickly
dark: up to ~25 min
Rhodopsin is bleached in bright light and needs to regenerate
38
What are the 3 color-specific cones?
red (long wavelength))
green (medium wavelength)
blue (short wavelength)
39
What causes color blindness?
mutations in cone opsins
40
In which cones are mutations most common?
red or green opsins
41
Colorblind people have normal ____ because rods are more sensitive than cones.
light sensitivity
42
red-green colorblindness; long-wavelength cone affected (red)
protanopia
43
red-green colorblindness; medium wavelength cone affected (green)
deuteranopia
44
a rare condition in which the individual only has one working type of cone
total color blindness (monochromacy)
45
Colorblindness is often inherited: ____ and ___. About __% males and __% females will inherit it.
x-linked
recessive
8
0.4
46
The human retina has ____ rods and ____ cones.
91 million
| 4.5 million cones
47
central retina where cones are highly packed; absolute center is completely rod-free
fovea
48
There is high ___ in the fovea and greater ____ in the periphery.
visual acuity
| light sensitivity
49
In the fovea, other cell layers are displaced. Why?
it allows light to hit cones with less interference
50
There are two types of bipolar cells. ON cells ___ with light while OFF cells ____ with light.
depolarize
| hyperpolarize
51
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.
```
AMPA
inotropic
depolarize
decrease
mGluR
metabotropic
hyperpolarize
increase
```
52
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.
```
low
AMPA
ionotropic
depolarize
decrease
mGluR
metabotropic
hyperpolarize
increase
```
53
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.
```
active
inactive
inactive
active
invert
```
54
Retinal ____ send APs to the brain and detect ____.
ganglion cells
| light intensity
55
the area to which a particular RGC is responsive
receptive field
56
Receptive fields have ___ and ___ portions. ON-center ganglion cells ___ when light goes on. OFF-center ganglion cells ___ when light goes on.
center
surround
depolarize
hyperpolarize
57
What is a post-inhibitory rebound?
stimulation of nerve impulses after hyperpolarization
58
In the direct pathway of information processing in the retina, the bipolar cells connect ____.
directly to ganglion cells
59
In the indirect pathway of information processing in the retina, the bipolar cells connect ____.
to horizontal and machine cells which make lateral connections to the ganglion cells
60
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 ___.
no inhibition
inhibition
well aimed small spots
contrast
61
In an OFF center RGC, dark light in the center leads to _____.
depolarization
62
Center-surround organization enhances sensitivity to ___ and ___.
edges
| contrast
63
RGCs fire depending on ___ not absolute ____.
contrast
| light intensity
64
Our visual system does not encode ____.
light intensity
65
streams of information related to different visual properties are dealt with simultaneously by different circuits
parallel processing
66
Receptive field properties get extracted as signal moves from photoreceptors to RGCs to brain and only ____ is transmitted.
relevant information
67
2 dimensional surface of the retina is mapped (topographically arranged) onto the surface of subsequent structures
retinotopy
68
All RGC axons exit the eye
| at the ____ (blind spot) and form a large, myelinated nerve called the ___.
optic disk
| optic nerve
69
point where optic nerve enters the brain
optic chiasm
70
The L visual field from ____ projects to R cortical hemisphere and vice versa.
both eyes
71
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.
```
optic tracts
ipsilateral temporal
contralateral nasal
lateral geniculate nucleus (LGN)
right
```
72
The right LGN projects to ___ in ___ of the cerebral cortex.
right visual cortex
| occipital lobe
73
Each LGN layer is eye-specific: ipsilateral eye projects to layers ___ and contralateral eye projects to layers ___.
2, 3, 5
| 1, 4, 6
74
Layers 1, 2 in the LGN are ___ (detect ___); receive input from ganglion cells that detect gross ___ and ____.
magnocellular
motion
shape
movement
75
Layers 3-6 are ___ (small cells, detect ___); receive input from ganglion cells that detect ___.
parvocellular
shape
shape
76
All layers of the LGN; detect color
koniocellular
77
___ RGCs innervate each LGN neuron and the visual receptive fields in LGN are almost ___ to those in retina.
1-2
| identical
78
Magnocellular layers have a ___ center surround and detect ___ bursts and are ___ to color.
large
transient
insensitive
79
Parvocellular layers have a ___ center surround and detect ___ bursts and are ___ to color.
small
sustained
sensitive
80
In the occipital lobe, the upper visual field is represented ___ the calcarine sulcus, the lower field ___.
below
| above
81
Fovea is represented on a huge amount of cortex because of its ___ and ___.
high sensitivity
| density of cones
82
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)
6
4
5
4C
83
allow for segregation of visual input from each eye
ocular dominance columns
84
Axons from L and R eye are ____ in layer 4.
segregated
85
What happens during monocular depravation (i.e., close one eye) during development?
lose ocular dominance columns
86
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?
convergence of several center surround cells --> orientation sensitivity
87
Some cells in V1 are also ___ selective; respond strongly to lines/bars/edges moving in a ___ but not at all in the ____.
direction
preferred direction
opposite direction
88
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.
```
binocular
aligned
disparity of the position
closer
beyond
```
89
What are the binocular cues?
convergence
| binocular disparity
90
What are the monocular cues?
```
linear perspective relative
size/height
shading
aerial perspective
texture
```
