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Intro to Brain and Behavior > Chapter 9: Vision Part 1 > Flashcards

Chapter 9: Vision Part 1 Flashcards

1
Q

What is visible light?

A

It is the electromagnetic energy that the human eye responds to.
ROYGBIV (R-having a lower energy and V-higher energy)

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2
Q

What is optics?

A

The study of light rays and their interactions

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3
Q

What is reflection?

A

Bouncing of light rays off a surface

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4
Q

What is absorption?

A

Transfer of light energy to a particle or surface

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5
Q

What is refraction?

A

Bending of light rays from one medium to another

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6
Q

What is the pupil?

A

Opening where light enters the eye

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7
Q

What is the conjunctiva?

A

Thin, transparent tissue covers the visible part of the sclera, and lines the inside of the eyelids

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8
Q

What is the sclera?

A

White of the eye

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9
Q

What is the iris?

A

Gives color to eyes

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10
Q

What is the cornea?

A

Glassy transparent external surface of the eye

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11
Q

What is the extraocular muscles?

A

3 pairs the move the eye in its orbit

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12
Q

What is the optic nerve?

A

Bundle of axons from the retina

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13
Q

What are lens?

A

They are suspended by zonule fibers attached to ciliary muscle.
Divides interior of eye into two compartments with different fluids.

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14
Q

What are the two different fluids of the eye?

A

Aqueous humor and Vitreous humor

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15
Q

What is aqueous humor?

A

It is watery, and nourishes cornea.
High pressure reduces blood supply and damages retina

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16
Q

What is vitreous humor?

A

It is jelly-like, keeps eye-ball spherical, 80% of volume of the eye, contains phagocytic cells that remove debris, and source of “floaters”

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17
Q

How does image formation of refraction by the cornea?

A

Eye collects light, focuses on retina (fovea), and forms image
Cornea performs most of the eye’s refraction
Re-shaped in Lasik

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18
Q

What is accommodation by the lens?

A

It is changing shape of leans. It provides extra focusing power required to bring near objects into focus on the retina

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19
Q

How do the lens act when looking at a far point?

A

The ciliary muscles are relaxed and the lens are flat.

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20
Q

How do the lens act when looking at a near point?

A

The ciliary muscles are contracted and allows elasticity of the lens to increase curvature

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21
Q

What does the pupil do in bright light?

A

The pupil is constricted.

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22
Q

What does the pupil do in dim light?

A

The pupil dilates.

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23
Q

What is the pupillary light reflex?

A

Shining a light into one eye causes constriction of both pupils

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24
Q

What is visual field?

A

The amount of space viewed by retina when one eye is fixated straight ahead about 150 degrees

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25
What is visual acuity?
The ability of the eye to distinguish two points close to each other.
26
What is visual angle?
The distance across the retina described in degrees
27
Where are the blood vessels not located?
Blood vessels are not in the center of the fovea but around the fovea
28
What is the retina?
A multilayered neural structure towards the back of the eye Converts optical image in to a neural image for transmission down the optic nerve to the brain for further analysis.
29
Where are the receptors found?
At the fovea
30
What is the optic disc?
It is a blind spot and the axons of ganglion cells go through it and enter optic nerve
31
What is the vertical information flow?
1. Transduction of the image by photoreceptors 2. Photoreceptors synapse on bipolar cells 3. Bipolar cells synapses on ganglion cells Forms the center of receptive field
32
What is the lateral information flow?
1. Photoreceptor 2. Horizontal cell 3. Bipolar cell 4. Ganglion cell Horizontal cells mediate an inhibition Forms the inhibitory surround of receptive field
33
Why so many types of cells in the retina?
Impossible to encode all the information in an optical image using a single neural image.
34
What are parallel pathways?
Retina uses different cell types to create parallel circuits for simultaneous transmission of multiple neural images to the brain.
35
What are rods?
More sensitive to light but there is only one rod pigment. You are using your rods only in scotopic vision and no color vision. Achromatic; one channel responding only to intensity
36
What are cones?
Less sensitive to light At high light level, you are using only cones Primates have three types of cones short (Blue), medium (green), and long (red)
37
What is the outer segment of a photoreceptor?
It is where the disks are located. It is where Na+ ions flow in through.
38
What is the inner segment of a photoreceptor?
It is where K+ ions flow out through.
39
Rods vs Cones
Both are photoreceptors Rods more sensitive to light meaning more disks and more photopigment to absorb light. Cones react to higher light
40
What type of receptors are used in scotopic vision?
Rods are used and no cones are used
41
What type of receptors are used in mesopic vision?
Rods and cones are used but poor color vision
42
What type of receptors are used in photopic vision?
Cones are the only receptors used.
43
What affects the resolution of a visual image?
The density and size of sensory receptors in the retina determine the resolution of visual image.2
44
What is the dark current?
Rods and cones are depolarized in darkness. Na+ ions flow in through channels in outer segment. K+ ions flow out through channels in inner segment. Na+ and K+ concentration are maintained by the Na+/K+ pump Mitochondria in inner segment provide ATP for pump
45
What happens when the receptor is absorbing light?
In the light, channels in outer segment close, cell hyperpolarizes.
46
What is rhodopsin?
It is visual pigment molecules that are in membrane discs. Formed by combining a chromophore with an opsin
47
What are visual pigment molecules?
Absorb the electromagnetic energy and divert the energy into a biological process
48
What is opsin?
A large, membrane bound protein, regulated biochemical processes within the cell
49
What is 11-cis retinalm (chromophore)?
It is the ligand for rhodopsin Changes shape when it absorbs a photon of light
50
What is the mechanism for phototransduction for photoreceptors (in the light)?
1. Light stimulation of rhodospin leads to activation of a G-protein, transducin 2. Activated G-protein activates cGMP PDE 3. Na+ channels are gated by cGMP 4. PDE hydrolyzes cGMP reducing its concentration (turns cGMP to GMP reducing its concentration) 5. This leads to closure of Na+ channels 6. Cell hyperpolarizes, transmitter release stops
51
What is the process of photoreceptors in the dark?
1. Concentration of cGMP is high 2. Inward Na+ current through cGMP-gated channels which depolarizes the cell. This is the dark current. 3. Depolarization causes transmitter release (glutamate) at terminal region
52
What are the OFF bipolar cells responses?
OFF bipolars depolarized by glutamate Hyperpolarized by light
53
What are the ON bipolar cells responses?
ON bipolars are hyperpolarized by glutamate Depolarized by light
54
What are glutamate two modes of action?
It is a ionotropic causing depolarization and metabotropic receptor causing hyperpolarization.
55
What are the glutamate ionotropic receptor effects?
Opens cation channels. Depolarizes OFF bipolar. Mostly for cones.
56
What are the glutamate metabotropic receptor effects?
Closes cation channels. Hyperpolarizes ON bipolar Mostly for rod cones
57
What way do we think of the receptive fields?
The set of photoreceptors to which the cell is connected. The part of the visual field in which various visual stimuli can affect the discharge rate of the cell
58
What is the receptive field?
Is of the ganglion cell that has a center and a surround and they are mutually antagonistic center-surround The center is much more sensitive than the surround, but the surround is many times larger than the enter. There are ON and OFF center types
59
What are characteristics of ON-centre cells?
The center has excitation to bright light. The surround has inhibition to dark.
60
What are the characteristics of OFF-centre cells?
The center has inhibition to dark. The surround is excited in the light.
61
What pathway does the surround uses?
The surround uses the lateral pathway
62
What pathway does the center uses?
The center uses the vertical pathway
63
What are P cells?
Small receptive fields Selective to particular wavelengths of light (color) Concerned with analysis of fine detail and color Are found in Parvocellular layers of LGN
64
What are M cells?
Large receptive fields Not wavelength selective Respond well to large objects and movement Are found in Magnocellular layers of LGN
65
What are Non-M Non-P retinal ganglion cells?
They are also called blue-yellow ganglion cells. They have small receptive fields Selective to particular wavelengths of light (blue and yellow) Found in the Koniocellular layer of LGN
66
What are the three signals of the visual system?
Luminance signal Red-green Blue-yellow
67
What is the luminance signal?
Black and white from red and green cones M-cells-luminance, motion
68
What is the red-green color signal?
Compare activity of red and green cones P-cells-fine detail
69
What is the blue-yellow color signal?
Compare activity of luminance signal and output of blue cones Non-M/Non-P cells
70
What is adaption?
The idea that a signal will adapt to prolonged stimulation. They would have a high firing rate, but they then adapt to decrease firing rate.
71
How is information organized leaving the retina?
The information is packaged into parallel pathways. So, each pathway of each ganglion cell is segregated.
72
What are the ON-center/OFF-center pathways role?
They signal increases and decreases in illumination
73
What are M/P/K pathways role?
M for motion, P (color), and non-M-non-P (color)
74
What are Left Eye/Right Eye pathways?
Each eye gives us a different view of the visual scene (important for depth perception)

Intro to Brain and Behavior (17 decks)

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