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INTRO TO NEURO ! > CHAPTER 10: VISION > Flashcards

CHAPTER 10: VISION Flashcards

1
Q

What is wavelength?

A

Related to perception of color / hue

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2
Q

What is amplitude?

A

related to perception of brightness

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3
Q

Pupil

A

Opening where light enters the eye

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4
Q

Iris

A

Controls the size of the pupil; gives color to the eyes

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5
Q

Cornea

A

Glassy transparent external surface of the eye; covers iris and pupil

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6
Q

Sclera

A

White part of the eye; tough wall of eyeball

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7
Q

Optic Nerve

A

Bundle of axons from the retina

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8
Q

Optic Disc

A

Blood vessels enter, optic nerve exits

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9
Q

Macula

A

Central vision / area around fovea

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10
Q

Fovea

A

Pit at center of retina; area of clearest vision

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11
Q

Macular Degeneration

A

leading cause of blindness in old age

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12
Q

Lens

A

Responsible for image formation and accommodation

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13
Q

Accommodation

A

The changing of shape of lens that allows for extra focusing power

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14
Q

Pupil

A

controls the amount of light that enters the eye (expands in dim light, constricts in bright light)

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15
Q

Pupillary light reflex

A

continuous adjustment to light travel, uses connection between retina and brain stem neurons that control muscle around pupil

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16
Q

Visual Field

A

Amount of space viewed by the retina when the eye is fixated straight ahead

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17
Q

Visual acuity

A

ability to distinguish two nearby points; sharpness/clarity of vision

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18
Q

Visual angle

A

distances across the retina described in degrees

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19
Q

Retina

A

Photoreceptors (rods and cones) are the transducers, ganglion cells carry output; axons from optic nerve, has five cell types that are arranged in layers

20
Q

What are the five cell types of the Retina?

A
  • ganglion cells
  • Amacrine cells
  • Bipolar cells
  • Horizontal cells
  • photoreceptors (cones and rods)
21
Q

Direct (vertical) pathway of the cells in Retina

A

Photoreceptors to bipolar cells to ganglion cells which project to the forebrain

22
Q

Horizontal cells

A

receive input from photoreceptors and project to other photoreceptors and bipolar cells

23
Q

Amacrine cells

A

receive input from bipolar cells and project to ganglion cells, bipolar cells, and other amacrine cells

24
Q

Rods

A
  • have rectangular segments
  • handle scotopic (night) vision
  • stop working in bright light
25
Q

Cones

A
  • have pointed segment
  • handle (photopic (daytime) vision
  • three types, each with their own pigment sensitive to different wavelengths
26
Q

Photoreceptors

A
  • convert light to neural signals
  • outer segments contain photopigment; only part of the eye that is sensitive to light
27
Q

Macula

A
  • has most of the discs
  • fovea is packed with tiny cones, each with its own ganglion cell
  • clear vision, color vision
28
Q

Peripheral retina

A
  • mostly rods
  • many photoreceptors converge on a single ganglion cell
  • more sensitive to light
  • detects motion
29
Q

Fovea

A
  • maximizes visual acuity
  • central fovea = all cones and area of highest visual acuity
30
Q

Phototransduction in Rods

A
  1. light changes retinals shape, deforming the rhodopsin to activate about 500 molecules of the G protein transducin - this activation causes a GTP molecule to replace a GDP molecule bound to transducin
  2. The activated transducins activate PDE molecules
  3. Each PDE molecule hyper polarizes, reducing its concentration
  4. Closure of Na+ channels and hyper polarization of the receptor
    - Photoreceptors hyper polarize in response to light, because light closes Na+ channels
    - photoreceptors depolarize in the absence of light
31
Q

Phototransduction in cones

A
  • similar to rods
  • different proteins involved: opsins
  • tuned to red, green, blue
  • population coding
32
Q

Receptive fields

A

stimulation in a small part of the visual field changes a cell’s membrane potential
- center : connections to bipolar cells
- surround : indirect connections via horizontal cells

33
Q

ON center bipolar cells

A

uses G - protein receptors and depolarizes when light is on (releases more Glu into ganglion cells)

34
Q

OFF center bipolar cells

A

uses Glu gated ion channels
and depolarizes when light is off (releases less Glu into ganglion cells)

35
Q

Pathway of bipolar cells

A

receptor, bipolar cell, ganglion cell

36
Q

Process of light hitting bipolar cell

A
  • photoreceptor releases glutamate when is depolarized
  • photoreceptor connects to both ON and OFF bipolar cells
  • bipolar cells connect to same type ganglion cells (ON & ON or OFF & OFF)
  • ON and OFF bipolar cells respond to glutamate in opposite ways
37
Q

How do ON bipolar cells respond to glutamate?

A

have metabotropic receptors and hyperpolarize to glutamate

38
Q

How do OFF bipolar cells respond to glutamate ?

A

have ionotropic receptors and depolarize to glutamate

39
Q

Ganglion cell receptive fields

A
  • tuned to detect light in specific locations
  • generate APs when depolarized
40
Q
A
40
Q
A
41
Q
A
42
Q

OFF center ganglion cell

A

black dot detector

43
Q

ON center ganglion cell

A

white dot detector

44
Q

What is the difference between bipolar and ganglion cells

A

bipolar cells generate graded local potentials whereas ganglion cells generate action potentials

INTRO TO NEURO ! (2 decks)

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