1
Q
pathway visual info to retina:
A
photoreceptors → bipolar cells → RGC
“Photoreceptors gossip, Bipolars pass it on, Ganglion cells scream.”
2
Q
Photoreceptors are (inhibitory or excitatory)
A
EXCITATORY!!! 🎉
“PHOto = PHO-sitive”
3
Q
Photoreceptors release ___ in response to dark:
A
GLU
“Dark Dumps, Light Less”
4
Q
Photoreceptors influence ____ for bipolar cells:
A
membrane potential
“Photo says ‘LIGHT!’ and Bipolar says ‘ALRIGHT!’ (and jumps UP).”
5
Q
Photoreceptors cause _____ to fire AP:
A
RGC’s
“PR starts the Party, RGC rings the Alarm”
6
Q
Two cells for retinal processing are:
A
- Horizontal
- Amacrine
HAM
7
Q
Horizontal cells are (inhibitory or excitatory)
A
INHIBITORY ↓↓↓↓↓
“HoriZONtal → Zaps Others Negatively.”
8
Q
Horizontal cells release less ___ in response to light:
A
GABA
“Give them LIGHT and they stop the GAB.”
9
Q
Amacrine cells are (inhibitory or excitatory)
A
INHIBITORY ↓↓↓↓↓
AmaCRIne = Creates Retinal Inhibition
10
Q
Amacrine cells release less ___ in response to light:
A
GABA
11
Q
T/F:
Photoreceptors are the only light sensitive cells.
A
TRUE
“Only PHOto gets the PHOton.”
12
Q
T/F:
RGCs and Bipolar cells are the only source of output from retina.
A
FALSE. Only RGC provides output.
“Only Ganglions Go.”
13
Q
Name three photoreceptor parts:
A
- outer (light membrane disk)
- inner (cell body and nucleus)
- synaptic terminal
“Oh, I See!”
14
Q
In bright light, rods (turn on or shut down)
A
shut down
Bright = Rods Break
15
Q
Name the three cone opsins:
A
blue, red, green
16
Q
T/F:
Cones require MORE photons than rods
A
TRUE.
“Cones need Crowds”
17
Q
The fovea is for: (two things)
A
acuity and color
18
Q
T/F:
The retina requires more rods than cones.
A
TRUE.
“Rods dominate the retina.”
19
Q
Opsins are in gene family:
A
7-TM
“Opsins Pass Seven Inner New Gateways”
20
Q
For rhodopsin, light is an (antag or ag)-onist
A
agonist
21
Q
Opsins use (metabotropic or ionotropic) receptors:
A
Metabotropic (GCPRs)
22
Q
In complete darkness, rods have a vM of:
A
-30mV (depolarized to resting potential)
23
Q
Rods depolarize in the dark due to:
A
dark-current (positive charge across membrane)
24
Q
Rods have a dark-current from:
A
special cGMP-gated Na+ channels
“Darkness Lets Sodium Drift In.”
25
Light (increases or decreases) levels of cGMP
decreases
“LIGHT LOWERS the LEVELS.”
26
When light shines on rods, the vM (hyper or de)-polarizes
hyperpolarizes (↓)
27
The two molecules that Rhodopsin consists of are:
1. opsins
2. retinals
RhodOPSIN = R → Retinal, OPSIN
28
Light changes two things for retinal:
1. to change shape
2. bleach rhodopsin
29
The 7 steps of phototransduction in rods are:
1. bleaching RHO
2. stimulating transducin (G-protein)
3. activating phosphodiesterase (PDE)
4. (PDE) cleaving cGMP
5. decreasing cGMP levels
6. cGMP channels close
7. vM hyperpolarizes
30
Light areas of the retina will have ___ cGMP and (in/de)-creasing vM
low ; de-
“Light = ↓cGMP & ↓vM.”
31
Dark areas of the retina will have ____ cGMP and (in/de)-creasing vM
high ; in-
“Dark = ↑cGMP & ↑vM"
32
What are the lengths of wavelength in this order: blue, green, red
short ; medium ; long
33
Give two reasons why cones can't saturate in daylight
1. less sensitive to light than rods
2. cones depend on day vision
34
The four main photopigment genes are:
1. L (long)
2. M (medium)
3. S (short)
4. OPN2 (RHO)
35
Dark adaptation is a result of (3 things)
1. dilated pupils
2. retinal adjustment
3. inactive RHO
36
Light adaptation relies on:
changes in Ca2+ concentration
37
The channel which conducts Ca2+ in cones is the:
cGMP-gate Na+ channel
38
Ca2+ affects cGMP by inhibiting:
guanylyl cyclase synthesis
39
Cones respond to (relative or absolute) light differences but not (relative or absolute) levels
relative (contrast) ; absolute (fixed/dim)
40
cones have (short or long) term memory
SHORT. cGMP and vM adapt quickly
41
The preferred stimulus of rods are (light or dark)
dark
42
The deepest cell in the retina is:
photoreceptors
43
Name the two cells light needs to pass before hitting the deepest cell:
RGCs and BP
44
There are ____ genes which encode every opsin
4
45
All photoreceptors are (hyper or de)-polarized by light
Hyper-
“Shine the light, shut GLU tight.”
46
When either rods or cones are switched from dark to light the immediate effect on these cells is _______ due to cleavage of cGMP.
Na+ channel closing and hyperpolarization
47
What property of cones is different from rods and causes cones to reactivate (become slightly more depolarized) after initially being hyperpolarized by the transition from dark to light?
decreased intracellular Ca2+ and increased cGMP (cGMP no longer inhibited by Ca2+)
48
An OFF-Center ganglion cell that is switched from light to dark at its visual field center will be ___________ .
depolarized (since light causes photoreceptors to hyperpolarize)
49
In rods, what is the immediate molecular consequence of photon absorption by rhodopsin?
Light on opsins will cause rhodopsin to bleach (CIS -> TRANS = turns it on)
50
Which G-protein is activated in the vertebrate phototransduction cascade, and what is its primary target enzyme?
Transducin (a G-protein) is activated and targets phosphodiesterase (PDE6).
Cascade: (Light → activates rhodopsin → activates transducin (G-protein) → activates PDE → reduces cGMP.)
51
Is cGMP activated in light?
No. It is broken down.
“PDE Puts cGMP Down.”
52
Photoreceptors are turned (on/off) in the light (de/hyper)-polarizing, and turned (on/off) in the dark, (de/hyper)-polarizing
on/hyper ; off/de
53
T/F:
The trichomacy theory uses population coding, similar to taste and smell.
TRUE (due to overlap of opsin, many cones will respond to one color)
54
In the light,
cones (de/act)-ivates PDE → (creating/destroying) cGMP
activate ; destroying
“Light activates PDE through transducin, and PDE breaks down cGMP — cones don’t destroy PDE; they use it.”
55
In the dark, cones can override cGMP destruction due to: (3 things)
1. reduced sensitivity of opsins
2. opsins gate Ca2+ and Na2+
3. Ca2+ inhibits guanylyl cyclase
56
In light, cones maintain a vM of ___:
-35
57
Light initially close the cone channels, like rods, but a
mechanism in cones allows cGMP to rise.
This then (opens / closes) the channel causing (hyper/de)-polarization so that cones can detect relative light differences (but rods( open / close) = (low / high) cGMP = (hyper/de)-polarized
opens ; de- ; closes ; low ; hyper-
“cGMP = channels Go More Positive.”
58
Cones can ______ adapt to light and dark areas in the field of
view.
Locally
59
Relative field mapping occurs by:
shining a light on retinal neuron, use electrode on optic nerve to track action potential, find center surround
60
Center of bipolar fields in PHOTORECEPTORS require (in/di)rect input:
direct
“Center sight uses the straight light.” (photo → bipolar)
61
Center surround in foveal bipolar fields receive input from many _____ fields, resulting in _____ _____:
receptive ; high acuity
62
Horizontal = Spread shade from ______ to side in the __________ layer
Photoreceptors ; ganglion
63
Amacrine = Chaos Ninjas from ______ to side in the _____ ______
Bipolar ; inner retina
64
Retinal field mapping showed that retinal neurons respond to: (2 things)
1. small circles of light
2. borders of light and dark
65
Photoreceptors are (hyper/de)-polarized in the light and (hyper/de)-polarized in the dark
hyper- / de-
66
Cones are (more/less) sensitive to light than rods.
LESS
67
Rods are completely hyperpolarized at _____mV
-65
68
While cones completely hyperpolarize at -55mV, what happens afterwards? Why?
They slowly depolarize due to quick-adjusting mV and cGMP levels
69
Center of bipolar fields in HC feedback onto p.recep require (in/di)rect input:
indirect
"Indirect means Scenic" (horiz = take extra cell route)
70
Direct (_____) vs Indirect (_____) have _____ effects on bipolar cells
center ; surround ; opposite
71
T/F:
With there being two different bipolar cells (ON vs OFF) that respond to light, one is for direct, the other for surround
FALSE. They are both direct, aka CENTER.
72
OFF-center cells respond to (light or dark)
DARK. Just like photoreceptors.
“OFF-center cells light up in the dark.”
(Imagine a neon “OFF” sign that glows only when the room goes dark.)
73
ON-center cells respond to (light or dark)
LIGHT.
“ON-switch glows in light.”
Picture a light switch that only flips ON when you shine a flashlight on it.
74
An ON-center bipolar cell is determined by two types of ____ cells
bipolar
75
T/F:
With there being two different bipolar cells that respond to light (On vs Off), one expresses a metabotropic receptor, the other ionotropic.
TRUE. OFF uses AMPA GLU, ON uses GLU.
76
OFF-surround cells respond to (light or dark)
LIGHT. Opposite of the OFF-center, which prefers dark
77
ON-surround cells respond to (light or dark)
DARK. Opposite of ON-center, which prefers light.
78
OFF-center bipolar cells use (ionotropic AMPA or metabotropic glutamate receptors)
Ionotropic AMPA glutamate receptors
_________________________________________________
“OFF uses AMPA—like flipping the AMP switch OFF.”
(AMPA has AMP, which sounds like “amp”—turning the amp OFF.)
79
ON-center bipolar cells use (ionotropic AMPA or metabotropic glutamate receptors)
Metabotropic glutamate receptors
__________________________________________________
“ON is ONly meta"
80
What is HAM's main function in retinal cells?
To detect edges in light and dark
81
T/F:
Ganglion cells fire AP no matter in light or dark. The only thing that changes in firing rate frequency.
TRUE
82
83
In an ON bipolar cell, what does the ON RGC do for GLU levels and vM?
GLU increases, depolarizes the cell
84
In an OFF bipolar cell, what does the OFF RGC do for GLU levels and vM?
GLU decreases, hyperpolarizes the cell
85
T/F:
The two bipolar components are angonists.
FALSE! They oppose one another so ANTAGONIST.
86
RGC's detect _____
edges
Neuro 3000
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