Vision Flashcards

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1
Q

What is the cornea?

A

Transparent surface that covers the pupil and iris

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2
Q

What is the sclera?

A

The white bit of the eye

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3
Q

What is the purpose of the lens?

A

To focus light rays on the retina (mine sucks because I need glasses)

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4
Q

What is the retina?

A

The internal lining of the rear 2/3 of the eye

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5
Q

What is the purpose of the retina?

A

To convert light energy into electrical impulses/neural activity

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6
Q

What is the macula?

A

The central area of the retina, it’s specialized for central vision

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7
Q

What is the fovea?

A

The center of the macula and retina, where the image is least distorted

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8
Q

What is the optic nerve made out of?

A

The axons of retinal ganglion cells

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9
Q

Where are the extraocular muscles located that enable the eye to move?

A

The sclera

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10
Q

What is light?

A

Electromagnetic energy emitted in the form of waves - different wavelengths appear as different colours

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11
Q

Which wavelengths of light are visible to the human eye?

A

400 - 700 nm

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12
Q

The flow of visual information within the retina

A

Photoreceptors to the bipolar cells to the ganglion cells

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13
Q

Two types of photoreceptors and their purpose

A

Rods: good for dim light (1000x more sensitive to light than cones)
Cones: good for color, transmit most of the visual information in bright light

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14
Q

Which kind of photoreceptors have the highest concentration in the fovea?

A

Cones! Rods are more common in the peripheral retina

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15
Q

What makes different cones sensitive to different wavelengths of light to enable colour vision?

A

Variations in photopigments (all rods have the same photopigment)

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16
Q

What are photosensitive retinal ganglion cells (pRGC)?

A

Sensitive to blue light, essential for circadian rhythm! (blue light is associated with morning)

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17
Q

Which has lower convergence and resulting higher acuity, rods or cones?

A

Cones!

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18
Q

Which three color frequencies can the cones in the human eye identify?

A

Blue, red, and green

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19
Q

What is the opponent process theory? How is it explained?

A

Color perception is controlled by the activity of two opponent systems (blue/yellow or red/green)
We never see certain color combinations, such as redish-green or yellowish-blue

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20
Q

Where is the blind spot located?

A

In the temporal hemiretina, where the retinal ganglion cells exit the retina (optic nerve)

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21
Q

What’s the difference between NT-gated K+ and Na+ channels?

A

NT-gated K+ channels: K+ moves out, causes hyperpolarization and is therefore inhibitory
NT-gated Na+ channels: Na+ moves in, causes depolarization and is therefore excitatory

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22
Q

Which types of cells carry information from your eyes to your brain?

A

Retinal ganglion cells

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23
Q

How are bipolar and ganglion cells arranged to allow light to strike the foveal photoreceptors directly?

A

They’re displaced laterally

24
Q

Do we consciously perceive a blind spot?

A

Nope! Our brain fills in the blanks

25
Q

How do images show up on the retina?

A

They’re inverted!

26
Q

What is the visual field?

A

The total amount of space that can be viewed by the retina (different for each eye)

27
Q

Where do the blood vessels in the eye originate from?

A

The optic disk (where the optic nerve fibres exit the retina and form the optic nerve)

28
Q

Are there blood vessels in the macula?

A

Nope!

29
Q

What is the half of the retina that is closest to the nose called?

A

The nasal hemiretina

30
Q

What is the half of the retina that closest to the temples called?

A

The temporal hemiretina

31
Q

Where do the axons of the ganglion cells from the nasal hemiretina cross the midline?

A

At the optic chiasm

32
Q

Do the axons of the ganglion cells from the temporal hemiretina cross the midline?

A

Nope!

33
Q

What happens if the left optic nerve is cut?

A

Vision in the left eye will be completely lost, which results in an overall loss of left peripheral vision

34
Q

What happens if the optic chiasm is transected?

A

Peripheral vision will be lost bilaterally, or in totality in both eyes

35
Q

What happens if the left optic tract is cut?

A

Vision of the right hemifield will be completely lost (one-half of vision)

36
Q

How does the name of the axons of the ganglion cells change as it crosses the optic chiasm?

A

Before chiasm, it’s the optic nerve.

After crossing the chiasm, it’s the optic tract

37
Q

What 2 places do the axons of the optic tract project to?

A

Superior colliculus and the LGN (in the thalamus)

38
Q

What are the 2 visual pathways?

A

Retinotectal pathway: subcortical vision

Retinogeniculostriate pathway: cortical vision

39
Q

What is involved in subcortical vision?

A

The retina and superior colliculus

40
Q

What is involved in cortical vision?

A

The retina, thalamus (LGN), and primary visual cortex

41
Q

What percentage of ganglion cells in the retina project to the superior colliculus?

A

About 10%

42
Q

Where do the most retinal ganglion cells synapse?

A

On Lateral Geniculate Nucleus (LGN) neurons in the thalamus

43
Q

Which LGN receives info about the left half of the visual field?

A

The RIGHT LGN

44
Q

Where do most neurons in the LGN project their axons to?

A

The primary visual cortex

45
Q

What is the first region of cortex to process visual info via the retinogeniculostriate pathway?

A

The primary visual cortex

46
Q

Where is the primary visual cortex located?

A

In the medial part of the occipital lobe, buried within the calcarine fissure

47
Q

What are 3 synonyms for the primary visual cortex?

A

Striate cortex, V1, Brodmann’s area 17

48
Q

How does the flow of visual information in the retina work?

A

From back to front! Photoreceptors are in the back, ganglion cells are in the front

49
Q

Follow the flow of cortical vision

A

Light to photoreceptors, to bipolar cells, to retinal ganglion cells which form the optic nerve, and after crossing the optic chiasm form the optic tract.
Optic tract leads to LGN in thalmus, then goes to primary visual cortex in occipital lobe, then goes to extrastriate cortex in the occipital, temporal, and parietal lobes

50
Q

What is the “phosphene threshold”?

A

The minimum TMS intensity that evokes phosphenes

51
Q

What does a lower phosphene threshold indicate?

A

A more excitable visual cortex

52
Q

How is ecstasy use correlated with phosphene threshold?

A

Negatively! More ecstasy use equals lower phosphene threshold

53
Q

Where is visual and auditory information integrated?

A

The superior colliculus

54
Q

What is the “ventriloquist illusion”?

A

When speech appears to be coming from the puppet’s mouth rather than the puppeteer’s mouth

55
Q

Which system is worse at localizing information: the auditory or visual system?

A

The auditory system is worse!

56
Q

Why does the “ventriloquist illusion” work?

A

Due to the sound source being mislocalized towards a synchronous but spatially discrepant visual event

57
Q

Where is most sensory information relayed through en route to the cortex?

A

The thalamus