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Psychology > Topic 3: senses - vision > Flashcards

Topic 3: senses - vision Flashcards

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1
Q

Explain the historical context of sensation

A
  • Democritus proposed we sense the external world in small copies = objects emit small replicas of themselves which then reach our senses allowing us to perceive and recognize them = what was believed until 18th century
  • Johannes Muller theorized in 1825 that stimuli reached sense organs produced responses in sensory nerves + different nerve = different sensations = brain can differentiate between light + sound
  • Muller’s idea remains as biological approach to sensation
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2
Q

How many of the sensory receptors of our body are in the eyes?

A

70%

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3
Q

What part of the brain is involved in perceiving + recognizing?

A

Cerebral cortex

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4
Q

Explain the visual stimulus of light

A
  • It is electromagnetic energy
  • Spectrum ranges from gamma rays - radio waves
  • Visible part is very small from 400nm-700nm
  • Ozone layer filters out energy from sun = 4/5 solar radiation reaching earth is wavelengths withing visible spectrum
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5
Q

What is sclera?

A
  • Tough outer coat = protect entire eyeball
  • White outer wall
  • Tough fibrous tissue
  • Extends from cornea -> optic nerve
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6
Q

What is choroid?

A
  • Vascular layer = contains blood vessels = nourish inner part of eye
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7
Q

What is cornea?

A
  • Front portion of eye
  • Convex bulging shape
  • Light enters eye through here
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8
Q

What is iris?

A
  • Located behind cornea
  • Regulates amount of light entering eye by adjusting size of pupil
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9
Q

What is pupil?

A
  • The hole in the middle of iris
  • Size increases/decreases depending on light intensity
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10
Q

Explain when mydriasis takes place

A
  • This is pupil dilation
  • Low light conditions = pupil enlarge for more light to enter eye = improve vision in dim light
  • Sympathetic NS activation = stress/excitement/fear lead to dilation due to fight or flight response
  • Medications/drugs = atropine + amphetamine side effect
  • Attraction/interest = studies suggest that seeing someone/thing that interests you causes dilation
  • Pain
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11
Q

Explain when miosis takes place

A
  • This is pupil constriction
  • Bright light conditions = pupil become smaller to reduce light entering to avoid damage to retina
  • Parasympathetic NS activation = relaxed physiological state can lead to constriction
  • Medication/drugs = opioids + pilocarpine side effects
  • Age = aging causes the muscles controlling pupils to not work as efficiently = pupil generally smaller
  • Accommodation reflex = constriction due to eye focusing on close object = due to reflex = changing of lens shape to focus on near objects
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12
Q

What is eye lens?

A
  • Transparent jelly-like substance made of proteins
  • Held in place by ciliary muscles + suspensory ligaments
  • Both adjust focal length of eye = see distant + nearby objects clearly
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13
Q

Define accommodation

A

Ability of eye to focus distant/nearby objects by changing focal length

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14
Q

What is aqueous humor?

A
  • Viscous liquid in between cornea + eye lens
  • Prevents eye from collapsing due to changes in atmospheric pressure
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15
Q

What is retina?

A
  • Delicate membrane at back of inner eye
  • Has many light sensitive cells = layer of tissue works like film of camera
  • Inverted real image is formed on retina = electrical signals generated by cell = sent to brain via optic nerve
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16
Q

What are the 2 types of light-sensitive cells?

A

1) Rods = respond to intensity of light
2) Cones = respond to color of object

17
Q

What is fovea?

A
  • Dimple in the middle of retina
  • Where vision is sharpest + most color perception
  • Max number of cones present
18
Q

What is optic disk?

A
  • AKA blind spot
  • All axons of ganglion cells exit retina = form optic nerve
  • There a small area in retina where optic nerve enters eye = insensitive to light = blind spot
19
Q

Explain how light is processed

A
  • Light hits posterior retina = spreads from photoreceptors -> bipolar cells -> innermost ganglion cells = generate APs
  • Axons of ganglion cells = thick optic nerve = leaves back of eyeball = carries impulses to thalamus -> visual cortex of brain
  • Thalamus = grey matter in forebrain = relays sensory signals
20
Q

What part of the brain is associated with visual processing?

A
  • Occipital lobe = contains visual cortex
  • Primary visual cortex = Brodmann area 17
21
Q

Describe the ventral stream in visual processing

A
  • Involved in processing color + texture + detail + shape + size
  • Damage impairs contrast sensitivity + color vision + depth perception + prosopagnosia
22
Q

Describe the dorsal stream in visual processing

A
  • Projects from visual cortex -> posterior parietal cortex
  • Involved in spatial processing = location + movement + spatial relations
  • Damage causes spatial disorders =
    simultanagnosia + optic ataxia + hemispatial
    neglect + akinetopsia + apraxia
23
Q

Describe function + sensitivity + location of cones

A
  • Function = preception of detail + color
  • Sensitivity = best under bright condition = high activation threshold
  • Location = central region of retina = contributes to central vision
24
Q

Describe function + sensitivity + location of rods

A
  • Function = vision in low light conditions + detect movement + peripheral vision
  • Sensitivity = highly sensitive to light allowing vision in dim conditions BUT can’t detect color ONLY variations of brightness = greyscale
  • Location = periphery of retina = more effective peripheral vision
24
Q

Describe cones

A
  • Approx. 6-7 million in the eye
  • Less sensitive to light than rods
  • Perceive changes more rapidly due to faster response time to stimuli compared to rods
  • 3 types = S/M/L cones = different pigment sensitive to specific wavelength range = short/medium/long wavelength
25
Q

Why do we have trichromic vision?

A
  • Humans have 3 kinds of cones with different photopsins = different responses to variation in color
  • 3 pigments responsible for detecting light vary in chemical composition = genetic mutations = people have cones with different color sensitivity
26
Q

Explain color blindness

A
  • Inherited
  • Due to destruction of cone cells
  • People unable to differentiate color e.g. red/green
  • Rare form = Daltonism = John Dalton found his grey jacket was red
  • Rare form = monochromacy = see world in greyscale
27
Q

What are some epidemiological stats on color vision?

A
  • Red/green = 7-10% men + only 0.4% women
  • Men get gene from mother’s father = genetic mutation on X chromosome
  • If women have on 1 X and not on other X it will overide
28
Q

Explain tetrachromatic vision

A
  • People with 4 or more types of cones
  • Mostly female
  • Color vision more intense
  • 15-47% women + 8% men are potentially tetrachromatic

Psychology (7 decks)

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