Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

PSYC 212 > Lecture 6: Retina > Flashcards

Lecture 6: Retina Flashcards

1
Q

Name teh 3 main parts of a photoreceptor

A

Outer segment
Inner segment
Synaptic terminal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Describe inner segment

A

Contains cell nucleus and synaptic terminals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Describe outer segment

A

Contains stack of disks packed with light sensitive pigment molecules (photopigemnts)
Responsible for phototrasnduction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Define phototransduction

A

Process by which photoreceptor cells in retina convert light into electrical signals - neural acitvity = can be processed by brain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Define photopigemnts

A

1st step visual process= chemical process in photoreceptors
Ligth sensitive molecule in photoreceptors composed of opsin and chromophore

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Define opsin

A

Protein sensitive to a specific wavelength of light
Protein component of photopigemnts, determines wavelength sensitivity of photoreceptor - enables colour and light detection, sensitivity to certain type of light

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Define chromophore

A

Light absorbing molecule within photopigments
Mammals = 11 cis retinal - changes shape upon light absorption

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Describe photopigemnt cycle - whole thing

A

Cycle of photoisomerization and regeneration = lets us see
11 cis retinal = receptive state —light—> photoisomerization = light changes shape of chromophore, isomerized = now all trans retinal - can no longer absorb light = bleached —> photopigment regeneration to get back to normal state —> 11 cis retinal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Define photoisomerization

A

Proces by which 11 cis retinal chromophore changes shape to all trans retinal when exposed to light = initiates phototransduction
Results in photoreceptor being bleached - renders it temporality unable to absorb more light

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Define photopigemnt regeneration

A

Process fo converting all trans retinal back to 11 cis retinal form
Allows photoreceptors to recover from bleaching and resume light detection
Occurs in retinal pigment epithelium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How does light become transduced into neuronal activity

A

When number of bleached photopigments reaches a THRESHOLD = photoreceptor will change rate at which it releases nts to indicate it has received light = light transduced into neural activity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How many types of opsin does each photoreceptor

A

Rods = have rhodopsin (498 nm)
Cones = 3 types of photopsin = wavelength specific= basis of colour perception

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Describe types of photopsin for cones

A

Short wave length specific cones = s-cones - perception of blue, 437nm
Medium = m-cones = green 533nm
Long = l-cones = red 564nm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What do some photoreceptor cells have

A

Melanopsin = can monitor ambient light levels = influence circadian rhythm
Unconscious perception of light cycle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Describe rods - when best

A

Sensitive to light intensities that are a million times smaller than the smallest intensity perceivable by cones
More sensitive
Fucntion better in low ligth conditions
Become overwhelmed = saturated in bright Environment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Describe cones - when best

A

Fucntion well in bright environment
Ineffective in low light conditions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Describe duplex retina idea

A

2 visual subsystems = bc differnce in light intensity between day and night = v large

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Define photopic vision

A

Vision under well lit conditions
Primialry mediated by cones
Enable colour perception and high visual acuity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Define scotopic vision

A

Vision in low light conditions
Mediated by rods
Provide high sensitivy to light but no colour perception
Hard to see detail

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Define dark adaptation

A

Process by which eyes adjust to low light conditions
Involves increased sensitivity of rods and shift from cone dominated to rod dominated vision
Can take up to 30mins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Name mechanism that allow us to see in dimly lit situations

A

Pupil dilation
Gain in sensitive of photoreceptors
Normalization through lateral inhibition

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Describe pupil dilation - see in dimly lit

A

Allows entry of more light = see Bette
Fastest mechanism
Effects relatively limited

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Describe gain in light sensitivity of photoreceptors - see in dimly lit

A

Dark environment associated with more regeneration than bleaching
Renders photoreceptors more receptive to light
Less receptors in bleached state in dark = more will be a viable to capture light

24
Q

Maximum sensitivity of cones

A

5-8mins in dark = cones stop adapting
Limit to sensitivy of light cones can have

25
Maximum sensitivity of rods
After 25 mins Rods = more sensitive
26
Rod cone break
After 7-8 mins inf ark Vision becomes dominated by rods Switch between photopic —> scotopic vision = duplex retina When rods become more sensitive than cones = because larger reservoir of photopigemnts than cones
27
Describe whole graph - for rod and cones and duplex retina idea
Cones = more sensitive at first, Rods = small number, all photopigments bleached in light BOTH increase sensitivity since less light can regenerate sensitive before they bleached But then rod cone break = rods become more sensitive Maximal visual sensitivity = due to rods
28
Define normalization through lateral inhibition
Neural mechanism in which active neurons suppress activity of neighbouring neurons Enhances contrast and improves detection fo edges and fine details Changes in luminence v large throughout day but visual system adapts fast via this mechanism
29
What is general principle lateral inhibition
Useful for enhancing contrast Subtracting and dividing by teh average luminance
30
Describe how we see outside vs inside
Measure background Not much contrast Would see this if visual system directly perceiving absolute intensity of light = would be very sensitive to big variations in light Imrpoatnt part = relative distance in luminence between surfaces = disregard illuminant
31
Describe normalzation through lateral inhibition
Put everything on common scale Remove average luminance = percieve difference in luminence between every point in visual field and average luminence Also used by decision making system - v widespread, relative value =important
32
What is enhancing contrast for
To see objects regardless of overal level illuminance
33
Define receptive field
Region on retina in which stimuli influence a neurons firing rate = increase or decrease it
34
Define ON CENTER OFF SURROUND cells
Activated by light in Center Inhibit by light in surround
35
Define OFF CENTER ON SURROUND CELLS
Opposite response = Activated by light in surround Inhibited by light in center
36
Light on center only - on center cells
Ganglion cell fires rapidly
37
Light on surround only - on center cells
Cell does not fire Bc on center off surround does not want light in surround
38
No light in center or surround - on center cells
Cell does not fire
39
Light on center and surround - on centre cells
Weak response = low frequency firing
40
Light on center only - off center cells
Ganglion cell does not fire
41
Light on surround only - off center cells
Cell fires rapidly
42
No light on center or surround - off center cells
Cell does not fire
43
Light on center and surround - off center cells
Weak response - low frequency firing
44
Describe enhancing contrast - 1
Once photoactivation starts Photoreceptors become hyperpolarized (negatively charged)
45
Describe enhancing contrast - 2
Changes in photoreceptor activation are communicated to the bipolar cells In form of graded potentials
46
Describe enhancing contrast - 3
Bipolar cells synapse with retinal ganglion cells Fire an all or non fashion, not like graded potentials
47
Define graded potentials
Gradual Not all or nothing = not like aps More nt= signal gradually increase as transmitted to bipolar cells
48
Describe what bipolar cells do generally for enhancing contrast
If light = photoreceptors hyperpolarized (-) Surround = no light = photoreceptors release nts On Center bipolar cells, activated, and reverse response = tell ganglion cell to fire ap If lots activity off center bipoalr cell will block it
49
Describe receptive fields and lateral inhibition - 1
To enhance contrast = use horizontal cells Light hyperpolarizes = renders polarity more negative of center cone Surround cone = connected to one horizontal cell Center cone connected to 2 horizontal Horizontal cells = communicate with many photoreceptors at once
50
Describe receptive fields and lateral inhibition - 2
On center bipoalr cells reverse the sign of the cone Off Center bipoalr cells would keep same sign
51
Describe receptive fields and lateral inhibition - 3
Dark depolarizes - renders polarity more positive of surround cones = + +
52
Describe receptive fields and lateral inhibition - 4
++ of surround cones = Activates horizontal cells = in turn inhibit all the cones Because center cone placed in middle of 2 horizontal cells = receives more inhibition than surround cones Center cone gets - - (- og) = 2 minus signs added bc connected to 2 horizontal cells
53
Describe receptive fields and lateral inhibition - 5
Amplifies bipoalr on cell activity = amplify retinal ganglion cell activity Specific configuration of center on off surround, activates these ganglion cells more 3 negs on center cone, additional inhibition = then reversed , so more activation = = bipolar cell gets 2 more + = INCREASES CONTRAST
54
Describe receptive fields and lateral inhibition - WHEN LIGHT ON CENTER AND SURROUND
All cones hyperpolarized Horizontal cell not activated = on center cone = - and on center bipoalr cell = + only (not super good)
55
Describe types of ganglion and bipolar cells
On center and off center On center bipoalr cells = reverse sign of photoreceptor Off Center bipoalr cells do not reverse sign of photoreceptor Allows black on white to stand out as much as white on black
56
Describe enhancing contrast - Mach bands
Greys are teh same but look diff Perceive more contrast than is Bc percieve light intensity diff Ex = B fire more than a, bc on Center, has highest ratio of light in Center and ark in surround = responsds more Same for D, = respond more than c bc n complement darkness, want more dark in surround
57
Describe enhancing contrast - Hermann grid
See dark in middle of lines when there is no dark Central vs peripheral vision - as move eyes = ones in periphery more affected by illusion In foveal vision = central vision = highest acuity, receptive field neurons = smaller More active on center off surround just to left pf gap = so the area right in center perceived as darker but then Respective fields smaller when look right at it = foveal vision

PSYC 212 (18 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions