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

Chapter 9: Vision Part 1 Flashcards

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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
Q

What is visual acuity?

A

The ability of the eye to distinguish two points close to each other.

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26
Q

What is visual angle?

A

The distance across the retina described in degrees

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27
Q

Where are the blood vessels not located?

A

Blood vessels are not in the center of the fovea but around the fovea

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28
Q

What is the retina?

A

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.

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29
Q

Where are the receptors found?

A

At the fovea

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30
Q

What is the optic disc?

A

It is a blind spot and the axons of ganglion cells go through it and enter optic nerve

31
Q

What is the vertical information flow?

A
  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
Q

What is the lateral information flow?

A
  1. Photoreceptor
  2. Horizontal cell
  3. Bipolar cell
  4. Ganglion cell
    Horizontal cells mediate an inhibition
    Forms the inhibitory surround of receptive field
33
Q

Why so many types of cells in the retina?

A

Impossible to encode all the information in an optical image using a single neural image.

34
Q

What are parallel pathways?

A

Retina uses different cell types to create parallel circuits for simultaneous transmission of multiple neural images to the brain.

35
Q

What are rods?

A

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
Q

What are cones?

A

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
Q

What is the outer segment of a photoreceptor?

A

It is where the disks are located.
It is where Na+ ions flow in through.

38
Q

What is the inner segment of a photoreceptor?

A

It is where K+ ions flow out through.

39
Q

Rods vs Cones

A

Both are photoreceptors
Rods more sensitive to light meaning more disks and more photopigment to absorb light.
Cones react to higher light

40
Q

What type of receptors are used in scotopic vision?

A

Rods are used and no cones are used

41
Q

What type of receptors are used in mesopic vision?

A

Rods and cones are used but poor color vision

42
Q

What type of receptors are used in photopic vision?

A

Cones are the only receptors used.

43
Q

What affects the resolution of a visual image?

A

The density and size of sensory receptors in the retina determine the resolution of visual image.2

44
Q

What is the dark current?

A

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
Q

What happens when the receptor is absorbing light?

A

In the light, channels in outer segment close, cell hyperpolarizes.

46
Q

What is rhodopsin?

A

It is visual pigment molecules that are in membrane discs.
Formed by combining a chromophore with an opsin

47
Q

What are visual pigment molecules?

A

Absorb the electromagnetic energy and divert the energy into a biological process

48
Q

What is opsin?

A

A large, membrane bound protein, regulated biochemical processes within the cell

49
Q

What is 11-cis retinalm (chromophore)?

A

It is the ligand for rhodopsin
Changes shape when it absorbs a photon of light

50
Q

What is the mechanism for phototransduction for photoreceptors (in the light)?

A
  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
Q

What is the process of photoreceptors in the dark?

A
  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
Q

What are the OFF bipolar cells responses?

A

OFF bipolars depolarized by glutamate
Hyperpolarized by light

53
Q

What are the ON bipolar cells responses?

A

ON bipolars are hyperpolarized by glutamate
Depolarized by light

54
Q

What are glutamate two modes of action?

A

It is a ionotropic causing depolarization and metabotropic receptor causing hyperpolarization.

55
Q

What are the glutamate ionotropic receptor effects?

A

Opens cation channels.
Depolarizes OFF bipolar.
Mostly for cones.

56
Q

What are the glutamate metabotropic receptor effects?

A

Closes cation channels.
Hyperpolarizes ON bipolar
Mostly for rod cones

57
Q

What way do we think of the receptive fields?

A

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
Q

What is the receptive field?

A

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
Q

What are characteristics of ON-centre cells?

A

The center has excitation to bright light.
The surround has inhibition to dark.

60
Q

What are the characteristics of OFF-centre cells?

A

The center has inhibition to dark.
The surround is excited in the light.

61
Q

What pathway does the surround uses?

A

The surround uses the lateral pathway

62
Q

What pathway does the center uses?

A

The center uses the vertical pathway

63
Q

What are P cells?

A

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
Q

What are M cells?

A

Large receptive fields
Not wavelength selective
Respond well to large objects and movement
Are found in Magnocellular layers of LGN

65
Q

What are Non-M Non-P retinal ganglion cells?

A

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
Q

What are the three signals of the visual system?

A

Luminance signal
Red-green
Blue-yellow

67
Q

What is the luminance signal?

A

Black and white from red and green cones
M-cells-luminance, motion

68
Q

What is the red-green color signal?

A

Compare activity of red and green cones
P-cells-fine detail

69
Q

What is the blue-yellow color signal?

A

Compare activity of luminance signal and output of blue cones
Non-M/Non-P cells

70
Q

What is adaption?

A

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
Q

How is information organized leaving the retina?

A

The information is packaged into parallel pathways. So, each pathway of each ganglion cell is segregated.

72
Q

What are the ON-center/OFF-center pathways role?

A

They signal increases and decreases in illumination

73
Q

What are M/P/K pathways role?

A

M for motion, P (color), and non-M-non-P (color)

74
Q

What are Left Eye/Right Eye pathways?

A

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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