Visual System Physiology Flashcards

1
Q

Photoreceptor cells are connected to?

A

Bipolar cells

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2
Q

Bipolar cells are connected to?

A

Ganglion cells

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3
Q

What cell’s axons form the optic nerve?

A

Ganglion cells

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4
Q

Where does the amount of rods peak?

A

20 degrees off center

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5
Q

Where does the amount of cones peak?

A

At the center - fovea

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6
Q

Cones are used for?

A

Color detection and visual acuity

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7
Q

Rods are used for?

A

Light detection and have a high sensitivity

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8
Q

Darkness does what to the photoreceptor cells?

A

Depolarizes

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9
Q

If a photoreceptor is depolarized, what will it release to the bipolar cell?

A

LOTS of glutamate

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10
Q

If LOTS of glutamate is released to a bipolar cell, what receptor will it bind?

A

mGLUR6

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11
Q

What is the action of mGLUR6?

A

It closes cGMP-gated sodium channels = bipolar cell is inhibited!

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12
Q

Light does what to the photoreceptor cells?

A

Hyperpolarizes

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13
Q

If a photoreceptor is hyperpolarized, what will it release to the bipolar cell?

A

LOW amounts of glutamate

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14
Q

If LOW amounts of glutamate are released to a bipolar cell, what happens?

A

The bipolar cell will spontaneously depolarize

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15
Q

If a bipolar cell depolarizes, it will release ____ to the ganglion cell and _____ it

A

Glutamate

Depolarize

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16
Q

What neurotransmitter do ganglion cells release?

A

Glutamate

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17
Q

What type of glutamate receptor does the ganglion cell have?

A

Normal - NMDA or non-NMDA that work to excite the cell with glutamate

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18
Q

What is the rate of glutamate release from photoreceptor cells?

A

Constant - only the amounts are changeable

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19
Q

What are some direct targets of the retina?

A
LGN
Superior colliculus
Pretectum
Hypothalamus
Accessory optic nuclei
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20
Q

Converge eyes to a point, controls focus, detects movement, maps position of objects around you

A

Lateral Geniculate Nucleus

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21
Q

What are the physiologic areas in the visual cortex?

A

V1, V2, V3A, V4, MT/V5

22
Q

V1’s job?

A

Identify edges and contours of objects

23
Q

V2’s job?

A

Depth perception

24
Q

V3A’s job?

A

Identify motion; as in did it happen or not? - no processing

25
Q

V4’s job?

A

Complete processing of color inputs

26
Q

MT/V5’s job?

A

Tracks motion across a scene in terms of directionality and context of background

27
Q

Lesion of V4 can result in?

A

Achromatopsia

28
Q

Achromatopsia

A

Problems seeing color especially if lesion is bilateral

29
Q

What is the organization of things in the 6 layers of the visual cortex?

A

Ocular dominance columns, orientation columns and blobs

30
Q

What do ocular dominance columns respond to?

A

Input from one eye or the other

31
Q

Ocular dominance columns and orientation columns run _______ to each other

A

Perpendicular

32
Q

Neurons in an orientation column are excited by?

A

Visual line stimuli of varying angles depending on the column

33
Q

Neurons in blobs are sensitive to?

A

Color

34
Q

What shape are blobs?

A

Cylindrical that drill down into the cortex

35
Q

Do ocular dominance columns, orientation columns and blobs span all layers of the visual cortex?

A

YES

36
Q

What are MG cells?

A

Melanopsin Ganglion cells

37
Q

What is special about MG cells?

A

They can directly sense light, specifically blue light

38
Q

What do MG cells help to regulate?

A

Circadian rhythm

39
Q

Where do MG cells project?

A

Hypothalamic suprachiasmatic nucleus in the pineal gland that releases melatonin

40
Q

Non-image-forming light responsive system?

A

Melanopsin ganglion cells

41
Q

Patient’s who are blind due to photoreceptor cell loss still have what?

A

MG cells, and thus are responsive to some blue light and have a circadian rhythm

42
Q

Where is the lesion if a patient is blind and lacks a circadian rhythm?

A

CN2 –affects all cells in the retina

43
Q

Why do older people experience sleep issues?

A

Their lens becomes more yellowish and decreases blue light transmission throughout the day

44
Q

Blue light exposure before sleep can _____ sleep

A

Disrupt

45
Q

Can treat seasonal depression, increase alertness and stimulate cognition

A

Blue light

46
Q

This pathway is the primary path for associating vision with movement

A

Dorsal pathway

47
Q

Dorsal pathway completes?

A

Motor acts based on visual imput

48
Q

What is the dorsal pathway steps?

A

V1 - V2/V3 - MT/V5 - Parietal lobe

49
Q

This pathway is the pathway that interprets images

A

Ventral pathway

50
Q

Ventral pathway recognizes?

A

Shapes, forms, faces

51
Q

What is the ventral pathway steps?

A

V1 - V2 - V4 - inferior temporal lobe

52
Q

What areas in the temporal lobe have their own area, thus if one is damaged the others may not be?

A

Copying objects, naming objects and facial recognition