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Neuro (Exam 3) > Vision Physio > Flashcards

Vision Physio Flashcards

1
Q

Where is light first refracted?

A

Cornea (about 2/3 of light is bent here)

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2
Q

Describe light bent in the lens

A
  • Adds variable amount of bending
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3
Q

A rounder lens means…

A

More refraction

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4
Q

A flatter lens means…

A

Less refraction

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5
Q

What happens with increasing curvature?

A
  • Ciliary muscle contracts
  • Suspensory l. loosens
  • Lens becomes more round
  • Near vision
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6
Q

What happens with decreasing curvature?

A
  • Ciliary muscle relaxes
  • Suspensory l. tightens
  • Lens pulled tight, loosening it
  • Far vision
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7
Q

Describe presbyopia

A

Lens stiffens w/ aging (losing elasticity)

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8
Q

What is the near response?

A
  1. Ciliary m. contracts
  2. Eyes converge to point of focus
  3. Pupil constricts
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9
Q

Vertically oriented cells of retina?

A
  • Receptor cells (cones/rods)
  • Bipolar cells
  • Ganglion cells
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10
Q

Horizontally oriented cells of retina?

A

Horizontal cells and amacrine cells

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11
Q

Path of light entering eye

A
  1. Receptor cell
  2. Horizontal cell
  3. Bipolar cell (MG cell)
  4. Amacrine cell
  5. Ganglion cell
  6. Vitreous
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12
Q

Which system has more convergence?

A

Rods

  • Many rods + many bipolars converge onto one ganglion cell
  • Dim light vision
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13
Q

Rod system… acuity or sensitivity?

A

Sensitivity

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14
Q

Which system relies less on convergence?

A

Cones

- One receptor - one bipolar cell - one ganglion cell

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15
Q

Cone system… acuity or sensitivity?

A

Acuity

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16
Q

Where do rods peak?

A

Around eccentricity of 20*

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17
Q

When is Glu release highest?

A

Darkness (when there is no stimulation by photons)

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18
Q

When is Glu release lowest?

A

Light (when there is stimulation by photons)

- Cells hyperpolarize

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19
Q

On-Center bipolar cell

A
  • Activation of center of RF causes depolarization

- Activation of periphery of RF causes hyperpolarization

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20
Q

What do on-center cells increase their discharge rate in response to?

A

Luminance increments

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21
Q

Off-center bipolar cell

A
  • Activation of center of RF causes hyperpolarization

- Activation of periphery of RF causes depolarization

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22
Q

What do off-center cells increase their discharge rate in response to?

A

Luminance decrements

23
Q

How does a on-center bipolar cell respond to cones in darkness?

A

Hyperpolarizes

24
Q

How does a on-center bipolar cell respond to cones in light?

A

Depolarizes

25
Q

How does a off-center bipolar cell respond to cones in darkness?

A

Depolarizes

26
Q

How does a off-center bipolar cell respond to cones in light?

A

Hyperpolarizes

27
Q

How do bipolar cells and ganglion cells interact?

A

Activated bipolar cell – Glu release – depolarizes ganglion cell – allows threshold to be reached – AP

28
Q

What do on-center cells tell us?

A

Where something IS

29
Q

What are on-center cells excited by?

A

Bright spot in RF

30
Q

What do off-center cells tell us?

A

Where something ENDS

31
Q

What are off-center cells excited by?

A

Dark spot in RF

32
Q

Role of amacrine and horizontal cells?

A

Provide inhibitory modulation of nearby cells in retina (via GABA or Gly)

33
Q

Role of Superior Colliculus?

A
  • Saccades

- Creates map of visual space to activate appropriate motor responses

34
Q

Role of pretectum?

A
  • Pupillary light reflex

- Sends projections to Edinger-Westphal then to ciliary ganglion

35
Q

Role of hypothalamus?

A

Circadian rhythms

36
Q

Role of LGN?

A
  • Control motions of eyes to converge on a point
  • Control focus of eyes based on distance
  • Determine position of objects in space and map them
  • Detect movement relative to object
37
Q

Brodmann area 17

A

Primary visual cortex

38
Q

Brodmann area 18

A

Parastriate cortex

39
Q

Brodmann area 19

A

Peirstriate cortex

40
Q

V1?

A

Primary visual cortex

41
Q

V2?

A
  • Greater part of Brodmann 18

- Depth perception (disparities between eyes)

42
Q

V3a?

A
  • Narrow strip of Brodmann 18

- Identification of motion

43
Q

V4?

A
  • Area 19

- Complete processing of color inputs

44
Q

V5?

A

Middle temporal area (19)

45
Q

Which layer receives input from LGB?

A

Layer IV

46
Q

What layers are the main output layers?

A

Layers V and VI

47
Q

What are ocular dominance columns?

A
  • Span all 6 layers

- Preferentially respond to input from one eye or the other

48
Q

What are orientation columns?

A
  • Span all 6 layers
  • Organized region of neurons that are excited by visual line stimuli of varying angles
  • Oriented perpendicular to cortical surface
49
Q

Where are orientation columns found?

A

Primary visual cortex

50
Q

What are blobs?

A
  • Span all 6 layers

- Organized region of neurons that are sensitive to color assemble into cylindrical shapes

51
Q

Main job of VI?

A

Identify edges and contours of objects

52
Q

Function of dorsal pathway?

A
  • WHERE
  • From primary visual cortex to parietal/frontal cortex
  • Associates vision with movement
  • Passes through V3
53
Q

Function of ventral pathway?

A
  • WHAT
  • From primary visual cortex to inferior temporal cortex
  • Interprets images and complex patterns
54
Q

Role of MG cells?

A
  • Subset of ganglion cells
  • Detects light directly via melanopsin
  • Light causes changes in Ca2+ levels in MG cells

Neuro (Exam 3) (15 decks)

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