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Neuro Test 3 > Physiology of the visual system > Flashcards

Physiology of the visual system Flashcards

1
Q

the fact or phenomenon of light being deflected in passing between one medium and another is the definition of?

A

Refraction

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2
Q

Where is the first site of refraction in the eye?

A

Cornea

2/3 of light bending

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3
Q

What adds a variable amount of light bending?

A

The lens

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4
Q

A rounder lens = ______ refraction

A

more

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5
Q

A flatter lens = _______ refraction

A

less

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6
Q

The ciliary muscle, suspensory ligaments allow for what?

A

The lens to curve

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7
Q

What muscle has to contract, to increase the curvature of the lens, leading to more refraction?

A

The ciliary mucle contracts, which allows the lens to loosen

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8
Q

What happens when the lens flattens(decreasing curvature) and therefore, decreasing refraction?

A

The ciliary muscle relaxes –> causing the suspensory ligaments to tighten and the lens is pulled tight

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9
Q

What is the term for when the lens becomes stiff with age and loses its elasticity?

A

Presbyopia

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10
Q

When focusing on a close object (the near response), what happens? (3)

A
  1. contraction of ciliary muscles (lens = rounder)
  2. convergence of eyes to point of focus
  3. constriction of pupil –> focus
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11
Q

Describe the path of light from where it enters the cornea to when it activates a photoreceptor:

A
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12
Q

There are 5 types of neurons in the retina, these are divided into either vertically oriented cells or horozontally oriented cells.

What 2 types are classified as horizontally oriented cells?

A

Horizontal cells

Amacrine cells

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13
Q

What 3 types of cells found in the retina are classified as vertically oriented cells?

A
  1. Receptor cells (rods + cones)
  2. Bipolar cells
  3. Ganglion cells (subtype = MG cells)
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14
Q

Rods utilize what property to allow them to operate in dim light?

A

Convergence

Many rods + bipolars –> one ganglion cell (sensitivity)

*cones do not do this*

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15
Q

Where are cones + rods the most dense in the retina?

A

Cones = fovea

Rods = outside ~ 20 degrees

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16
Q

What are rods + cones constantly releasing?

A

Glutamate!

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17
Q

When is glutamate released the most?

A

In the dark

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18
Q

How much glutamate is released when the cells are hyperpolarized?

A

a little bit of glutamate is released when there is light

light = little

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19
Q

Cones allow in light (photons) which do what to the photoreceptors?

A

Causes them to hyperpolarize, which decreases glutamate release

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20
Q

What are the 2 types of bipolar cells?

A

ON-center

OFF-center

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21
Q

Which part of an ON-center cell is depolarized upon its activation?

A

The center

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22
Q

What does an OFF-center cell mean?

A

Its depolarized in the periphery.

And hyperpolarized in the center

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23
Q

How is a bipolar cell depolarized?

A

The glutamate receptor in depolarizing bipolar cells is a GPCR and when it sees light it closes its channel, so less glutamate gets through.

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24
Q

In which type of bipolar cell does a sign change occur?

A

Depolarizing bipolars

25
Q

What type of glutamate receptor is found in hyperpolarizing bipolar cells?

A

Common, excitatory glutamate receptor (non-nmda: ampa + kainate)

26
Q

Dark + ON-center =

A

Hyperpolarized

27
Q

Light + ON-center =

A

Depolarized

28
Q

Light + OFF-center =

A

Hyperpolarized

29
Q

Dark + OFF-center =

A

Depolarized

30
Q

In order to see in “low-light” situations, many rods converge onto a ____ cell.

A

ON-center bipolar cell

31
Q

What is the function of the ON + OFF center cells?

A

To help us increase our ability to detect edges + sharpen our vision

32
Q

What do ON-center cells tell us?

A

Where something is

(excited by bright spot)

33
Q

What do OFF-center cells tell us?

A

Where something ends

(excited by dark spot)

34
Q

What are the direct targets of the retina?

A

Lateral geniculate body

Superior Colliculus

Pretectum (pupillary light reflex)

Hypothalamus

Accessory optic nuclei

35
Q

What is the function of the lateral geniculate body?

A
  1. Control the motions of the eyes to converge on a pointo of interest
  2. Control the focus based on distance
  3. Create a map of objects in space
  4. Detect movement relative to an object
36
Q

Area 17 =

A

Primary visual cortex

37
Q

Area 18 =

A

Parastriate cortex

38
Q

Area 19 =

A

Peristriate cortex

39
Q

V1 =

A

Primary visual cortex (area 17)

40
Q

V2 + V3 =

A

Brodmann 18

41
Q

V4 =

A

area 19

42
Q

V5 =

A

middle tempoaral + 19

43
Q

Which layer recieves input from LGB?

A

Layer 4

44
Q

Which layers are the main output layers?

A

5 + 6

45
Q

Where are the ocular dominance (one column = one eye L or R) columns found?

A

The primary visual cortex

46
Q

What columns are oriented perpendicular to the cortical surface + excited by visual line stimuli?

A

Orientation columns

(ex. vertically responsive orientation columns see things running up + down)

47
Q

What layer are columns found in?

A

They span all 6 layers of the cortex!

48
Q

Organized regions that are sensitive to color are called?

A

Blobs (in the primary visual cortex)

49
Q

Red cones =

A

564 nm

50
Q

Green cones =

A

~ 500 nm

51
Q

Blue cone =

A

437 nm

52
Q

How are these 3 things mapped?

  1. ocular dominance columns
  2. Orientation columns
  3. Cytochrome oxidase
A
  1. stripes
  2. swirls
  3. blobs
53
Q

What is the major function of V1 of the primary visual cortex?

A

To identify edges + contours of objects

54
Q

What is the function of V2?

A

Depth perception (via looking at the disparities between the two eyes)

55
Q

What is the function of V3a?

A

Identification of motion

56
Q

What is the funcion of V4?

A

Color input

57
Q

The dorsal “where” pathway runs from _____ to ______.

Function?

A

Primary visual cortex –> parietal/frontal cortex

It passes through V3 to complete motor acts based on visual input.

58
Q

The ventral “what” pathway runs from ______ to ________.

Function?

A

From primary visual cortex to inferior temporal cortex

Interpretes images + patterns (copying/naming objects + facial recognition)

59
Q

What is the importance of the non-image-forming light-responsive melanopsin ganaglion cells?

A

Help synchronize circadian rhythms via melanopsin stimulating MG cells w/ Ca+

(might be another photosensitive cell (like rods + cones–> project onto hypothalamus))

Neuro Test 3 (18 decks)

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