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Psyc 369 > Chapter 2 > Flashcards

Chapter 2 Flashcards

1
Q

What is vision?

A

Reflected light from objects

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2
Q

What is light?

A

A series of wavelengths within the electromagnetic spectrum (x-rays, gamma, UV rays etc).

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3
Q

What is the wavelength of visible light?

A

370-730nm.

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4
Q

What colours are seen at which wavelengths?

A

Blue-Around 300-400 nm. Green-500nm Yellow-600nm. Red-700+

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5
Q

What is colour?

A

Colour isn’t an actual thing-our rods and cones detect different wavelengths and the brain creates the colour.

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6
Q

What is a photon?

A

A single “particle” of light- the smallest possible quantity.

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7
Q

What is the optic array?

A

Spatial pattern of lightrays entering your eye from different locations on a scene-the array varies in space and time, depends on objects position, shape, texture etc.

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8
Q

What is the field of view?

A

Portion of space surrounding you that you can see without moving your eyes.

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9
Q

What are the angles of a humans field of view?

A

FOV-190 degrees. 60 degrees upwards, 80 degrees down.

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10
Q

What traits of vision does something with eyes on the side of its head have?

A

Greater FOV, poor depth perception.

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11
Q

Why don’t crocodiles have forward facing eyes, when most predators do?

A

Because they are ambush predators and don’t have a need to be super accurate, as they don’t chase their prey.

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12
Q

What are the 3 layers of membranes in the eye?

A

Sclera- Outermost, includes white of eye and cornea
Choroid- Middle layer, contains mostly blood vessels, oxygen and nutrients.
Retina- Inner layer, made up of neurons (rods and cones).

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13
Q

What are the 3 pairs of extraocular muscles?

A

Superior-inferior rectus- Rotates the eyeball up and down
Medial and lateral rectus- rotates eye towards and away from centre (toward/away from nose).
Superior/Inferior Oblique- Rotates eye clockwise/counterclockwise.

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14
Q

What is the cornea and what does it do?

A

The protective bump at the front of the eye. It sharply bends light- is part of the process of focusing light onto the retina.

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15
Q

Is the cornea or the lens more responsible for focusing power?

A

Cornea, which is responsible for 80% of focusing power.

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16
Q

What is the pupil and what is it’s function?

A

Literally just a hole in the middle of the eye. It allows light to enter the eye. Contract when it’s really bright out, and dilate when it’s dark (pupillary reflex).

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17
Q

What is the iris and what does it do?

A

Coloured part of eye, controls dilation or constriction of pupils using muscles.

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18
Q

What is the lens and what does it do?

A

Elastic, crystalline structure that also helps focus light onto retina-focuses it precisely onto the retina.

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19
Q

What is accommodation?

A

When the lens changes shape to focus light from different distances onto the exact right spot. Light from distant objects comes into the eye at a parallel angle and is bent slightly to hit the retina. Closer objects, the light comes in at an outward angle and has to be bent more to focus.

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20
Q

What is the shape of the lens controlled by?

A

The ciliary muscle.

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21
Q

What happens when the lens becomes thicker vs thinner?

A

Thicker-bends light more to focus on close objects. Ciliary muscles contract, zonule fibres relax.
Thinner-Bends light less to focus on distant objects. Ciliary muscles relax, zonule fibres contract.

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22
Q

How is the retinal image created?

A

All the light rays reflected by a specific point on an object are directed by the lens onto corresponding points on the retina- as a result, the image on the retina becomes inverted (upside-down and backwards).

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23
Q

What are the structures of the retina and what do they do?

A

1) Photoreceptors- rods and cones, create the image
2) Horizontal cells- make lateral connections
3) bipolar cells- make through connections
4) Amacrine cells- Lateral connections
5) Ganglion cells- through connections, include the optic nerve.

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24
Q

How many rods/cones are there in the eye?

A

Rods-120 million

Cones-6 million

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25
Q

Which photoreceptor is more light sensitive?

A

Rods-thus they have better vision in the dark.

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26
Q

Which photoreceptor has better acuity?

A

Cones-can see more details

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27
Q

Which photoreceptor has more convergence and why is this good/bad?

A

Rods- signals from the rods converge on a single ganglion, which makes it so rods are more sensitive, but less attentive to detail.
Cones each connect to their own ganglion, which makes sensitivity poor, but they have way better attention for detail-cone has to see more light to fire and cause its ganglion to fire.

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28
Q

What is convergence?

A

The combination of signals to create excitation.

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29
Q

What is the fovea centralis?

A

Small area (1mm squared) in the centre of the retina. Cones are here, rods are not. Involved in directed looking, great visual acquity, highest density of photoreceptors. Each one connects to one bipolar and one ganglion cell.

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30
Q

What is the blind spot of the eye?

A

Area for the ganglion cell axons which make up the optic nerve to exit the eye-normally we are not aware of it. Small hole with no photoreceptors makes up blind spot.

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31
Q

What is transduction?

A

The transformation of a physical stimulus into a neural signal.

32
Q

What are the responsibilities of the photopigments?

A

To change the shape of a photon entering the eye (photoisomerization), which triggers a chain reaction releasing millions of charged molecules, which eventually causes the rod/cone to fire.

33
Q

What are photopigments comprised of and are they all similar?

A

Retinal and Opsin. They all differ, in terms of regeneration rate, spatial sensitivity, and molecules.

34
Q

What is the refractory period in rods and cones?

A

Photopigment has to return to it’s original state to fire. The refractory period for rods is 30 mins, for cones is 7mins.

35
Q

What is dark adaptation?

A

A progressive increase in sensitivity to light.

36
Q

What is the dark adaptation curve and how do we manipulate it?

A

Graph showing how sensitivity to light changes overtime. First, determine threshold for light by getting a participant to stare at a small X, turn on light at the side of X, find threshold using method of adjustment. Continue adjusting.

37
Q

Is the increase in sensitivity to light smooth?

A

No. It does change overtime, but not smoothly.

38
Q

What is cone adaptation?

A

When the participant looks directly at the light, activating only the cones-eventually sensitivity stops changing after around 7 mins (refractory period).

39
Q

What is Rod monochromat?

A

Someone who only has rods, sensitivity to light becomes VERY increased as they stay in the dark, and increases smoothly.

40
Q

What is the rod-cone break?

A

For the first 7 minutes, we see with our cones-their maximum sensitivity is low. After around 7 minutes, we see with our rods-rod sensitivity is greater.

41
Q

Why does the curve generate?

A

Due to differences in pigment regeneration. In bright lighting, more pigments are used up, so if it suddenly goes dark, the probability of hitting a “ready” photopigment is less likely, and our sensitivity to light is low. In the dark, more photopigments regenerate without firing. More photopigments become ready to fire, thus making things more sensitive.

42
Q

What is spectral sensitivity?

A

The relationship between sensitivity to light and wavelength of light.

43
Q

Where is sensitivity highest?

A

Around 560nm. (yellow-greenish)

44
Q

What is the Purkinje effect?

A

Difference in peak sensitivity between rods and cones: Rods-500nm. Cones-560nm. Reds, Oranges, and Yellows are brightest during the day, Blues and greens are brightest at night!

45
Q

What colour are we most sensitive to?

A

Yellow! We see it as the brightest, but it’s not actually, we’re just the most sensitive to it.

46
Q

What colours of light are rods and cones most/not sensitive to?

A

Cones- most sensitive to reddish-green light

Rods-most sensitive to bluish light-RODS CANT SEE RED

47
Q

What is the absorption spectra?

A

Shows that differences in spectral sensitivity are due to differences in absorption spectra of pigments- how much light of different wavelengths is absorbed.

48
Q

What amount of light are short wavelength cones the best at absorbing?

A

420nm

49
Q

What is convergence?

A

The number of presynaptc neurons converging on a single post-synaptic neuron-there are around 126 million receptors and only 1 million ganglion cells.

50
Q

Which type of receptor has the most convergence?

A

Rods-makes them much more sensitive to dim light as they can combine sensory inputs.

51
Q

What is an advantage of having no convergence?

A

Greater visual acuity (cones), as cones each connect to their own ganglion, you can actually tell which cone is firing and which isn’t.

52
Q

What is strabismus?

A

A disorder of the extraoccular muscles-the two eyes do not point in the same direction, resulting in double image and impaired depth perception. NOT the same as a lazy eye.

53
Q

What is the difference between strabismus and a lazy eye?

A 
Strabismus-2 signals are sent to the brain, causing confusion due to competing images.
Lazy eye (amblyopia)-brain ignores signals from one of the eyes
54
Q

What is myopia?

A

Nearsightedness-light from distant sources is focused in front of the retina, due to an elongated eye.

55
Q

What is hyperopia?

A

Farsightedness-Light from nearby sources is focused behind the retina-often caused by short eye length or aging.

56
Q

What is presbyopia?

A

A type of hyperopia where the lens loses it’s elasticity, stops becoming as thick.

57
Q

What are cataracts?

A

Progressive clouding of the lens.

58
Q

What is macular degeneration?

A

Damage to the photoreceptors in the central area of the eye. Caused by environmental damage/genetics-develop a grey blob in vision.

59
Q

What is Retinitis Pigmentosa?

A

Inherited condition of gradual degeneration from out to in. Leads to night blindness and tunnel vision.

60
Q

What is astigmatism?

A

An irregularly shaped cornea.

61
Q

What are image enhancement night vision goggles?

A

Requires at least some visual light-photons reflected from objects are focused into intensifier tubes, converted into electrons, and amplified. This is why you could blind someone if you shine a light into it.

62
Q

What is thermal imaging in night vision goggles?

A

Convert infrared wavelengths into visible spectrum-works even without visible light.

63
Q

What are glial cells?

A

“Nurse cells,” take care of neurons (give nutrients, clean toxins, glue neurons together). There are 1 trillion of them in the brain compared to 100 billion neurons.

64
Q

What is the difference between sensory, association, and motor neurons?

A

Sensory neurons look different, have no dendrites, as it doesn’t receive input from other neurons-instead has a touch receptor!

65
Q

How often does an action potential fire at light vs hard pressure?

A

Light-Fires less frequently. High-Fires more frequently (at a maximum rate, firing rate becomes evenly spaced due to each action potential running up against the refractory period-doesn’t happen at low pressure)

66
Q

What is spontaneous activity?

A

Firing of a neuron in the absence of stimulation-firing is random but occurs at a given rate.

67
Q

How do our receptors fire with vision?

A

Firing rate codes for both brightness and wavelength. If all 3 receptors are firing at equal amounts, you get black, grey, or white (low amounts-black and grey. High amounts-white) Brightness is coded average firing rate, wavelength is coded by the pattern of neurons firing (relative firing rate of 3 cone types).

68
Q

What is the synapse?

A

A tiny space between the axon terminals of one neuron and the dendrites of the next neuron.

69
Q

What are neurotransmitters?

A

Chemical substances that help neurons “communicate” with other neurons.

70
Q

What are the 5 major steps of communcation with neurotransmitters?

A

1) Synthesis-neurons make neurotransmitter. 2) Store in synaptic vesicles. 3) Release- when action potential reaches the axon terminals of the pre-synaptic neuron, the vesicles float down to the ends and pop, neurotransmitter released into synaptic cleft 4) Binding-attach to special receptors on post-synaptic neuron. 5) Deactivation-receptors and neurotransmitters are “pulled apart” ending the signal.

71
Q

What is excitation?

A

Makes post-synaptic neuron more likely to fire-binding with receptor site causes some sodium to enter the post synaptic neuron (depolarization).

72
Q

What is graded potential?

A

When the action potential gets close to threshold, but doesn’t actually hit it.

73
Q

What are the 2 ways to generate enough excitation for a neuron to fire?

A

1) Spatial summation-Add up excitatory inputs from different neurons to make post-synaptic neuron fire. 2) Temporal summation- Neuron A fires multiple times ina row, builds up the potential (adds up excitation over time) to reach action potential.

74
Q

What is inhibition?

A

Post-synaptic neuron becomes less likely to fire-makes inside even more negative (hyperpolerization)

75
Q

Can neurons be both excitatory and inhibitory?

A

YES. It depends on the receptor site (Alpha side can be excitatory, beta side can be inhibitory.

Psyc 369 (11 decks)

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