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MED 104- MEDICAL PSYCHOLOGY > 3. LIGHT AND VISION > Flashcards

3. LIGHT AND VISION Flashcards

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1
Q
  1. Where does a person’s knowledge about the world around it come from?
A
  • from its sense
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2
Q
  1. What did Democritus (a Greek philosopher) propose with regards to vision?
A
  • he believed that we sensed the external world by means of small, faint copies of objects that are transmitted from the objects to us
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3
Q
  1. What idea did Johannes Muller propose in 1825 with regards to senses?
A
  • he believed that the stimuli reaching our organs produce responses in sensory nerves
  • different nerves evoke different types of sensations
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4
Q
  1. What can the brain differentiate between?
A
  • it can differentiate between light and sound
  • this is because the different energies stimulate different nerves
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5
Q
  1. Which system in the body do human beings depend on the most?
A
  • the visual system
  • the visual system provides us with the richest variety of environmental input
    (colour, movement, spatial depth perception are all processed simultaneously)
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6
Q
  1. What is the most studied and best understood of our senses?
A
  • the visual system
  • our knowledge of the anatomy and coding mechanisms from the visual receptor
  • through the central pathways
  • into the cerebral cortex
  • is better studied than any other sensory system
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7
Q
  1. What percentage of sensory receptors of the whole body are in our eyes?
A
  • 70%
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8
Q
  1. What part of the brain is needed to get involved in order to perceive or recognize something?
A
  • nearly half of the cerebral cortex needs to get involved
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9
Q
  1. Which sense is considered the dominant sense?
A
  • vision
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10
Q
  1. What is light?
A
  • it is a form of electromagnetic energy
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11
Q
  1. Which points does the electromagnetic spectrum range from?
A
  • it ranges from y-rays to AM waves
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12
Q
  1. What is the visible part of the electromagnetic spectrum range?
A
  • it is very small
  • it ranges from about 400 nanometers to a little over 700 nanometers
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13
Q
  1. List the forms of light waves on the electromagnetic spectrum from the weakest (longest) to the strongest (shortest).
A
  • Radio waves
  • Microwave
  • Infrared
  • Visible
  • Ultraviolet
  • X-Ray
  • Gamma Ray
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14
Q
  1. What filters out much of the energy arriving from the Sun?
    What does this result in?
A
  • the Ozone layer of the Earth’s environment does this filtering
  • it results in 4/5 of the solar radiation reaching the surface of the earth to consist of wave lengths within the visible spectrum
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15
Q
  1. What is the sclera of the eye?
A
  • it is the tough outer coat that protects the eyeball
  • it is the white outer wall of the eye
  • it is a tough fibrous tissue that extends from to the cornea to the optic nerve at the back of the eye
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16
Q
  1. What is the Choroid?
A
  • it is the vascular layer of the eye
  • it contains the blood vessels that nourish the inner parts of the eye
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17
Q
  1. What is the Cornea?
A
  • it is the front portion of the eye
  • it is a convex shape
  • it bulges outside
  • light enters through the cornea
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18
Q
  1. What is the Iris?
A
  • it is located just behind the cornea
  • it regulates the amount of light that enters the eye
  • it does this by adjusting the size of the pupil
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19
Q
  1. What is the pupil?
A
  • it is the hole in the middle of the iris
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20
Q
  1. What does the pupil do with regards to the intensity of light entering the eye?
A
  • it increases or decreases
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21
Q
  1. What happens when a high intensity of light enters the eye?
A
  • the pupil size decreases
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22
Q
  1. What happens when low intensity light enters the eye?
A
  • the pupil size increases
  • the pupil size can also increase when you are excited or sexually aroused
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23
Q
  1. What is the eye lens made up of?
A
  • it is made up of a transparent jelly like substance
  • this substance is made up of proteins
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24
Q
  1. How is the eye lens held in position?
A
  • it is held in position by the ciliary muscles
  • the suspension ligaments
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25
Q
  1. What is the role of the ciliary muscles and the suspensory ligaments?
A
  • they adjust the focal length of the eye
  • this is so that we can see distant and nearby objects clearly
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26
Q
  1. What is accommodation?
A
  • the ability of the eye to focus on distant and nearby objects
  • it does this by changing the focal length
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27
Q
  1. What is the Aqueous humor?
A
  • it is a viscous (stick) liquid
  • it is filled in the area between the cornea and the eye lens
  • it prevents the eye from collapsing due to the changes in the atmospheric pressure
28
Q
  1. What is the Retina?
A
  • it a the delicate membrane
  • it has a large number of light- sensitive cells
  • it is situated at the back of the inner eye
29
Q
  1. What are the two types of light-sensitive cells?
A
  • rod cells
  • cone cells
30
Q
  1. What are rod cells?
A
  • they are cells that respond to the intensity of light
31
Q
  1. What are cone cells?
A
  • they are cells that respond to the colour of the objects
32
Q
  1. What is found in the middle of the retina?
A
  • a tiny dimple
  • this is know as the fovea or the fovea centralis
33
Q
  1. What is the fovea?
A
  • it is the center of the eyes sharpest vision
  • it is the location of the most colour perception
34
Q
  1. What is present in the Fovea?
A
  • the maximum number of cones
35
Q
  1. What kind of image is formed on the retina when we look at an object?
A
  • an inverted real image of the object is formed
36
Q
  1. Which signals are generated by the cells in the eye?
    Where are they sent to and how are they sent?
A
  • electrical signals are generated by the cell in the eye
  • they are sent to the brain through the optic nerve
37
Q
  1. What is the Optic Disk also known as?
A
  • the blind spot
  • this is where all of the axons of the ganglion cells exit the retina
  • these ganglion cells form the optic nerve
38
Q
  1. What is the blind spot?
A
  • it is a small region in the retina
  • it is where the optic nerve enters the eye
  • it is insensitive to light
39
Q
  1. What happens when an individual has just been hit with a blinding flash light beam?
A
  • the light hits the posterior retina
  • it spreads from the photoreceptors to the bipolar cells
  • these bipolar cells are just beneath the photoreceptors
  • this light continues to spread to the ganglion cells
  • this light then generates action potentials within the ganglion cells
40
Q
  1. What do the axons of the ganglion cells do?
A
  • they weave together
  • this creates the thick ropey optic nerve
    ( this is also known as the cranial nerve)
  • this optic nerve leaves through the back of the eyeball
41
Q
  1. What does the optic nerve carry?
    Where does it carry it to?
A
  • the optic nerve carries the impulses up to the thalamus
  • it then goes to the brains visual cortex
42
Q
  1. What is the thalamus?
A
  • it is the massive gray matter located in the forebrain
43
Q
  1. What are the functions of the thalamus?
A
  • the thalamus have several functions
  • such as relaying sensory signals
    (including pain and visual perception)
44
Q
  1. What is the occipital lobe of the mammalian brain associated with?
A
  • it is associated with visual processing
  • it contains most of the anatomical region of the visual cortex
45
Q
  1. What is the primary visual cortex?
A
  • the Broadmann area 17
  • also known as V1 (Visual one)
46
Q
  1. Where are the cone and the rod photoreceptors located?
    What do they do?
A
  • they are located near the retina center
  • they detect fine detail in colour
47
Q
  1. When do cones hit their activation thresholds?
A
  • they hit them in bright conditions
  • this is because cones are not very sensitive
48
Q
  1. What are some characteristics of rods?
A
  • they are more numerous
  • they are more light sensitive
  • they cannot pick up on real colour
  • they only register a grayscale of black and white
  • they are situated around the edges of retinas
  • they rule the peripheral vision

PERIPHERAL VISION:
the ability to see things where you are not directly looking

49
Q
  1. How many cones are there roughly in the human eye?
A
  • about six to seven million
50
Q
  1. What are some characteristics of cones?
A
  • they are less sensitive to light than the rod cells in the retina
  • they allow the perception of colour
  • they are able to perceive finer details and more rapid changes in images
  • this is because their response time to stimuli is faster than that of rods
51
Q
  1. How many types of cones are there?

Name them

A
  • there are three types:
    1. S- Cones
    2. M- Cones
    3. L- Cones
52
Q
  1. What is each type of cone sensitive towards?
A
  • they are sensitive to visible wavelengths of light
  • these wavelengths of light correspond to short- wavelengths, medium- wavelength and long-wavelength light
53
Q
  1. What do these three types of different cones have?
A
  • they have different types of photo receptors
  • they have different types of response curves
  • they respond to a variation of colour in different ways
54
Q
  1. What is trichromatic vision?
A
  • it is vision that involves three independent channels for conveying colour information
  • these channels are derived from the three different types of cone cells in the eye
55
Q
  1. What does genetic mutation vary with regards to trichromatic vision?
A
  • genetic mutations result in the three pigments responsible for detecting light to have variations in their exact chemical compositions
  • different individuals will have different cones with different colour sensitivity
56
Q
  1. What is colour blindness/colour vision deficiency?
A
  • it is an inherited and rarely acquired eye condition
57
Q
  1. What causes colour blindness in an individual?
A
  • it is a result of the destruction of cone cells from diseases
58
Q
  1. What is the most usual form of colour blindness?
A
  • Daltonism
  • it was named after John Dalton
  • he found out about this condition at the age of 26
  • this was when he accidentally understood that his grey jacket was actually dark red
59
Q
  1. What is colour blindness the general name for?
A
  • it is the general name for all deficiencies related to the ability to see different colours
  • it can manifest itself in several ways

(some colour blind people cannot distinguish from shades of red)

(others cannot distinguish between shades of purple or green)

60
Q
  1. What is the most unusual form of colourblindness?
A
  • Monochromacy
  • people suffering from it see most of the world in black and white
  • this is a condition of almost total colourblindness
  • this is when two or more of the light sense cones do not work
61
Q
  1. What percentage of Red-Green colour blindness affects men?
A
  • 7-10%
62
Q
  1. What percentage of Red-Green colour blindness affects women?
A
  • 0.4%
63
Q
  1. How does Red-Green colour blindness genetically occur in men?
A
  • most men get the gene from their grandfather on their mother’s side
  • it is a genetic mutation on the X chromosome
  • this means that they will have this characteristic in their phenotype if it occurs in their genotype
  • they will then experience colour blindness
64
Q
  1. Why does Red-Green colour blindness genetically not occur in women that often?
A
  • women have two X chromosomes
  • some women will have one X chromosome with the genetic mutation on it
  • their other X chromosome will not have a genetic mutation on it
  • this will override the phenotype of Red Green colour blindness
  • the condition will not manifest itself
65
Q
  1. What is Achromatopsia?
A
  • this is a rare condition
  • it is the inability to see the world in any other colour except black and white
66
Q
  1. What is tetrachromatic vision?
A
  • people with this condition have four or more types of cones
  • this occurs when someone (almost always a female) has a fourth type of cone cell
  • these people have a more intense vision
67
Q
  1. Label the eye diagram below.
A
  1. Conjunctiva
  2. Iris
  3. Lens
  4. Pupil
  5. Cornea
  6. Conjunctiva
  7. Sclera
  8. Optic Disc
  9. Optic Nerve
  10. Macula
  11. Retina
  12. Choroid
  13. Ciliary Body
  14. Vitreous Body
  15. Anterior Chamber

MED 104- MEDICAL PSYCHOLOGY (29 decks)

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