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PSYCH 367 > Lecture 3 Eye/Retina > Flashcards

Lecture 3 Eye/Retina Flashcards

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1
Q

TRUE or FALSE: gamma rays are short and radio waves are long

A

true

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2
Q

What is the range of the visible spectrum for humans?

A

400 to 700 nm

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3
Q

light enters the eye through the _______ and is focused by the _______ and the ________ to a sharp image on the _________.

A

pupil, cornea, lens, retina

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4
Q

What are the visual receptors in the retina called?

A

rods and cones

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5
Q

How many rods and cones are in the human eye?

A

120M rods, 6M cones

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6
Q

shape of rods and cones?

A

rods are large and cylindrical; cone are small and tapered

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7
Q

what is destroyed first in macular degeneration? What aspect of vision does it affect? Who is it most common in?

A

fovea and small surrounding area are destroyed; high acuity vision; older individuals

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8
Q

What is destroyed first in retinitis pigmentosa? What aspect of vision does it affect? What can also be destroyed? What is its main cause?

A

rods are destroyed first; night vision; FOVEAL cones; genetic

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9
Q

Why don’t we notice the blind spot?

A
  • one eye covers the blind spot of the other
  • it is located towards the edge of our visual field
  • brain fills in missing information by extrapolating what’s around it (top-down processing)
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10
Q

The _________, which is fixed, accounts for about 80% of the focusing power of our eye

A

cornea

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11
Q

The __________, which adjusts shape for object distance, accounts 20% of the focusing power of our eye

A

lens

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12
Q

TRUE or FALSE: we can see near objects clearly when our lenses are relaxed

A

FALSE: far away objects

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13
Q

_____________ occurs when ciliary muscles are tightened.

A

accommodation

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14
Q

TRUE or FALSE: the lens thickens during accommodation

A

TRUE

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15
Q

Explain accommodation.

A
  1. ciliary muscles tighten
  2. lens thickens
  3. lens focus light rays
  4. near objects focused on retina
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16
Q

Myopia occurs when the image gets focused _____________ the retina.

A

in front of

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17
Q

refractive myopia vs axial myopia

A
  • refractive myopia: cornea or lens bends too much light
  • axial myopia: eyeball is too long
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18
Q

hyperopia occurs when the image gets focused ___________ the retina.

A

behind

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19
Q

What is also known as old eye?

A

presbyopia

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20
Q

Presbyopia occurs when the lens _________________________ .

A

can no longer adjust for close objects

21
Q

What is presbyopia caused by?

A

hardening of lens and weakening of ciliary muscles

22
Q

TRUE or FALSE: opsin is a light sensitive molecule.

A

FALSE: retinal

23
Q

What is visual transduction?

A

occurs when the retinal absorbs one photon, causing it to change shape (isomerization)

24
Q

What is dark adaptation?

A

process of increasing visual sensitivity after switching from high to low-level lighting conditions

25
Q

What are the steps to determining the dark adaptation curve?

A
  1. observer starts in lit room and becomes ‘light adapted’
  2. lights turned off, observer adjusts intensity of a test light until it is just barely visible (determines their sensitivity at the beginning of the curve)
  3. as time passes, they continue to readjust intensity of the test light
26
Q

How do you measure cone vs. rod vs. both for sensitivity in dark adaptation?

A
  • cone: participant looks directly at light
  • rod: participant must be rod monochromat
  • both: participant fixates on point while light is shined from the side
27
Q

How long does stage one of the dark adaptation curve take place for?

A

3-4 mins

28
Q

How long does the rod-cone break of the dark adaptation curve last for?

A

7-10 mins

29
Q

How long does stage 2 of the dark adapation curve last for?

A

20-30 mins

30
Q

What is the process needed for transduction?

A
  • retinal changes shape
  • opsin separates
  • retina shows visual pigment bleaching
  • retinal and opsin recombine during REGENERATION (to respond to light again)
31
Q

TRUE or FALSE: as our vision improves in the dark, visual pigments regenerate at a slower rate than they are being used

A

FALSE: faster rate

32
Q

What is spectral sensitivity?

A

sensitivity of rods and cones to different parts of the visible spectrum

33
Q

___________________ light can be used to determine threshold at different wavelengths, for spectral sensitivity.

A

monochromatic

34
Q

TRUE or FALSE: threshold is the same as sensitivity

A

FALSE: threshold is the reciprocal of sensitivity

35
Q

Draw the spectral sensitivity curve vs the threshold curve.

A

spectral peak is up, threshold peak is down

36
Q

Which colour/part of the visible spectrum are humans most sensitive to? is this where the lowest or highest threshold is?

A
  • greenish/yellow (middle)
  • lowest threshold (for highest sensitivity)
37
Q

TRUE or FALSE: rods are more sensitive to short-wavelength light.

A

TRUE

38
Q

At what wavelength are rods and cones most sensitive?

A
  • rods at 500 nm
  • cones at 560 nm
39
Q

What is the Purkinje shift? Provide an example.

A
  • enhanced sensitivity to short wavelengths during dark adaptation when the shift from cone to rod vision occurs
  • blue seems brighter to a dark-adapted eye vs light-adapted eye
40
Q

At which 3 wavelengths do cone pigments absorb best?

A

419 nm, 531 nm, 558 nm

41
Q

rods and cones send signals vertically through which cells?

A

bipolar and ganglion

42
Q

rods and cones send signals horizontally through which cells?

A

horizontal and amacrine

43
Q

There is higher convergence in __________ than ________.

A

rods, cones

44
Q

Describe the convergence of rods vs cones to ganglion cells.

A
  • 120 rods: 1 ganglion cell
  • 6 cones: 1 ganglion cell
45
Q

TRUE or FALSE: cones in the periphery have a one to one relation to ganglion cells

A

FALSE: cones in the fovea

46
Q

TRUE or FALSE: more convergence of rods = less sensitive

A

FALSE: more sensitive

47
Q

TRUE or FALSE: less convergence of cones = lower acuity

A

FALSE: better acuity

48
Q
A

PSYCH 367 (22 decks)

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