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Perception Midterm > Chapter 2 - Wayne's Notes > Flashcards

Chapter 2 - Wayne's Notes Flashcards

1
Q

What is the distinction between sensation and perception?

A

Sensation - a stimulus transduction process where light energy is changed into a neural impulse that is processed by the brain
Perception - second part of the process where the neural code is processed and organized, and meaning is attributed to the information

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2
Q

Light energy

A

Very small portion of the electromagnetic spectrum we can see

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3
Q

Visible light

A

Depends on the organism and its survival requirements

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4
Q

Fibrous tunic

A

Sclera and cornea

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5
Q

Cornea

A

Involved in 80% of refraction

Nourished by the aqueous humor

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6
Q

Middle layer

A

Vascular tunic with choroid and ciliary body

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7
Q

Choroid

A

Blood vessels that nourish photoreceptors
Absorbs light not transduced by photoreceptors
Reduces scatter and sharpens the image

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8
Q

Nocturnal animals and reflective layers

A

Makes them more sensitive to light in low cdtns but they lose acuity

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9
Q

Ciliary body

A

Makes aqueous humor

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10
Q

Anterior chamber

A

Aqueous humor

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11
Q

Aqueous humor

A 
Supplies oxygen and nutrients
Carries away waste on cornea and lens
Helps maintain shape and permits appropriate refraction
Too little pressure = reduced vision
Too much pressure = glaucoma
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12
Q

The iris

A

Regulates amount of light permitted into the light by blocking it

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13
Q

Layers of the iris

A
  1. Outer layer - pigment

2. Inner layer - blood vessels

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14
Q

The pupil

A

Where light enters the eye

Sensitive to light waves, autonomic nervous system activity and depth of field requirements

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15
Q

Muscles of the pupil

A
  1. Circular, around the outside of the hole: contracts to reduce light into the eye
  2. Radial to circular muscles: contract to let more light into the eye
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16
Q

The lens

A

Focuses light directly onto retina
Contains the crystalline structure
Transparent

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17
Q

Crystalline structure

A
  1. Capsule
  2. Epithelial layer
  3. Lens itself
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18
Q

Capsule

A

Thin and elastic
Controls flow of aqueous humor into lens and holds the shape
Allows variation in thickness and influences accommodation

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19
Q

Sclerosis

A

Hardening of the lens
Produced by old cells in outer epithelial layer which become more densely packed
Cells are constantly produced at the edges, older cells are in the center

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20
Q

Epithelial layer

A

Produces new cells

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21
Q

Cataracts

A

Opacity of the lens

22
Q

Brunescence

A

Accumulation of yellow pigment in lens which affects vision

23
Q

Vitreous chamber

A

Thin membrane anchored to inner wall of the eye

Contains vitreous fluid

24
Q

Floaters

A

Crystallized bits of fluid that cast shadows on the retina

25
Q

The retina

A

Responsible for transduction and initial info processing

Neural tissue grown forward

26
Q

Photoreceptors

A

On the outer segment
Face away from incoming light
Located at the back of the eye

27
Q

Bipolar cells

A

Pass info from photoreceptors -> retinal ganglion cells

28
Q

Amacrine and horizontal cells

A

Modify and combine signals from photoreceptors before they are passed to ganglion cells

29
Q

Macula

A

Center of the eye, contains the fovea

1.5mm in diameter

30
Q

Optic disk

A

Axons of the retinal ganglion cells leave from here
Contains blood vessels supplying the retina
Blind spot of the eye

31
Q

Retinal blood supply

A

2 separate ones

  1. Choroidal circulation system - primarily for nourishing photoreceptors
  2. Retinal circulation system
32
Q

What happens when lightwaves are focused on the retina?

A

Forms a retinal image
The quality of this initial image is the first step of determining the quality of vision
If properly focused, preserves the spatial structure of environmental input

33
Q

Refraction

A

Cornea performs most of it

Remaining refraction is done by the lens

34
Q

Accommodation

A

Change in lens shape that refracts light for acuity

35
Q

Presbyopia

A

Eye loses ability to accommodate

36
Q

Myopia

A

Image focused in front of the retina

Nearsightedness

37
Q

Hyperopia

A

Image focused behind the retina

Farsightedness

38
Q

Photoreceptors

A

Rods and cones

Transduce light waves into neural code, which is sent to brain for more processing

39
Q

Rods

A

Mainly found in periphery, 20-30 degrees from fovea

40
Q

Cones

A

Primarily in the fovea, density drops off

Acute and fine vision

41
Q

Transduction

A

Occurs because of the interaction of light waves with light-sensitive molecules in photoreceptors

42
Q

Photopigments

A

Light-sensitive molecules in photoreceptors

43
Q

G-proteins

A

Light stimulation of photorecptor activates these

44
Q

Membrane potential of outer rod segment

A

30mv

45
Q

Dark current

A

Depolarizations caused by steady inflow of Na+ through outer membrane channels
Stimulated by cyclic guanosine monophosphate (cGMP)

46
Q

cyclic guanosine monophosphate (cGMP)

A

Stimulate sodium channels in rods

47
Q

Step of transduction

A
  1. Absorption of a photon by rhodopsin (rods)
  2. Absorption leads to change in conformation of retinal, activates opsin and causes bleaching
  3. This activates transductin
  4. Transductin activates phosphodiesterase
  5. PDE breaks down cGMP in rod
  6. Reduction in cGMP closes Na+ channels
  7. The membrane is hyperpolarized, like a cascade)
  8. Many G-proteins are activated by each photopigment molecule
    This allows to detect even just one photon of light
48
Q

Rhodopsin

A

Receptor protein with prebound chemical agonist

49
Q

Opsin

A

Receptor protein with seven transmembrane alpha helices

50
Q

Retinal

A

Prebound chemical agonist of rhodopsin

51
Q

Bleaching

A

The activation of opsin

Changes the pigment from purple to yellow because of the wavelengths absorbed by rhodopsin

Perception Midterm (5 decks)

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