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Physiology of Behaviour > Chapter 6: Vision > Flashcards

Chapter 6: Vision Flashcards

1
Q

What is a sensation?

A

It involves the cells of the nervous system that are specialized to detect stimuli from the environment.

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2
Q

What is perception?

A

It is the conscious experience and interpretation of information from the senses and involves neurons in the central nervous system.

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3
Q

What do photoreceptors do?

A

They detect the presence of light stimuli.

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4
Q

What is visible light?

A

It includes the portion of the spectrum that is detected by the photoreceptors of an organism.

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5
Q

What wavelength of electromagnetic radiation is visible to us?

A

Electromagnetic radiation with a wavelength of between 380 and 760 nm is visible to us.

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6
Q

What is light?

A

Light is a range of wavelengths.

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7
Q

What are the three dimensions that determine the perceived colour of
light:

A

Hue, saturation, and brightness.

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8
Q

_____ oscillations lead to longer wavelengths, and _____ ones lead to shorter wavelengths.

A

Slower; faster

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9
Q

What is hue?

A

It is the first of the three perceptual dimensions; determined by wavelength of light.

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10
Q

What is brightness?

A

It is the second perceptual dimension of light; determined by the intensity of light.

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11
Q

If the intensity of the electromagnetic radiation is _____, the _____ increases, too.

A

Increases; apparent brightness

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12
Q

If all the radiation is of one wavelength, the perceived colour is _____. Conversely, if the radiation contains all visible wavelengths, it produces _____

A

Pure or fully saturated; no sensation of hue, it appears white

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13
Q

What is saturation?

A

It refers to the relative purity of the light that is being perceived.

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14
Q

What are sensory receptors?

A

They are specialized neurons that detect a variety of physical events; where we receive information about the environment.

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15
Q

What is a sensory transduction?

A

It is when sensory events are transduced (“transferred”) into changes in the cells’ membrane potential.

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16
Q

What are receptor potentials?

A

They are electrical changes. They affect the release of neurotransmitters and can modify the pattern of firing in neurons with which cells form synapses.

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17
Q

What is a retina?

A

It is the inner lining of the eye. It is a part of the CNS, the brain.

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18
Q

In the retina, an image causes what?

A

In the retina, an image causes changes in the electrical activity of millions of sensory receptors, which results in messages being sent through the optic nerves to the rest of the brain.

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19
Q

What are orbits?

A

They are bony pockets in the front of the skull; where the eyes are suspended.

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20
Q

What holds and moves the eyes in place, and is attached to the sclera?

A

Six extraocular muscles

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21
Q

What is a sclera?

A

It is the tough, white outer coat of the eye.

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22
Q

What does the sclera do?

A

It is opaque and doesn’t permit entry of light in the eye.

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23
Q

What is a cornea?

A

It is the transparent outer layer at the front of the eye.

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24
Q

What is a pupil?

A

It is an opening in the iris which size regulates the amount of light that enters.

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25
Q

What is a lens?

A

It is situated immediately behind the iris, and consists of a series of transparent, onionlike layers.

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26
Q

What is an iris?

A

It is the pigmented ring of muscles behind the cornea.

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27
Q

What are ciliary muscles?

A

It can alter the shape of the lens by contraction.

28
Q

What is an accommodation?

A

It is the process in which the changes in shape permit the eye to focus images of near or distant objects on the retina.

29
Q

What is a vitreous humor?

A

It is a clear gelatinous substance that fills the main part of the eye.

30
Q

What happens after the light passes through the lens?

A

After passing through the lens, light traverses the main part of the eye, which is filled with vitreous humor. After passing through the vitreous humor, light falls on the retina.

31
Q

What are rods and cones?

A

They are receptor cells, collectively known as photoreceptors, that are located in the retina. They detect light and transduce it into receptor potentials.

32
Q

What are the 3 main cellular layers of the human retina?

A

The photoreceptive layer, the bipolar cell layer, and the ganglion cell layer.

33
Q

What does the muscle and bones surrounding the eye do?

A

They aid in focusing an image on the retina.

34
Q

How many cones and rods does the human retina contain?

A

The human retina contains approximately 120 million rods and 6 million cones.

35
Q

Describe cones

A

They are prevalent in the central retina, including the fovea, and are responsible for color vision and acuity.

36
Q

What is fovea?

A

It is the central region of the retina, which mediates our most acute vision, and contains only cones. They are also responsible for our color vision.

37
Q

What is color vision?

A

It is our ability to discriminate light of different wavelengths.

38
Q

Describe rods

A

They are sensitive to low intensity light but do not contribute to color or high acuity vision.

39
Q

What is an optic disk?

A

It is located at the back of the eye, where the axons conveying visual information gather together and leave the eye through the optic nerve.

40
Q

Why does the optic disk produce a blind spot?

A

It produces a blind spot because no receptors are located there.

41
Q

What are bipolar cells?

A

They are neurons whose two arms connect the shallowest and deepest layers of the retina.

42
Q

What are ganglion cells?

A

They have neurons whose axons travel through the optic nerves and carry visual information into the rest of the brain.

43
Q

Explain how the three main cellular layers form synapses.

A

Photoreceptors form synapses with bipolar cells, and bipolar cells form synapses with ganglion cells.

44
Q

Describe horizontal and amacrine cells.

A

They are contained in the retina, which transmit information in a direction parallel to the surface of the retina and thus combine messages from adjacent photoreceptors.

45
Q

What is a photopigment?

A

It is a special chemical involved in the first step in the chain of events that eventually leads to visual perception; embedded in the lamellae.

46
Q

What is lamellae?

A

They are thin plates of membrane that make up the outer segment of photoreceptors.

47
Q

How many photopigment molecules does a single human rod contain?

A

It contains approximately 10 million photopigment molecules.

48
Q

Two parts of photopigment molecule

A

It include an opsin (a protein) and retinal (a lipid).

49
Q

What is a rhodopsin?

A

It is a photopigment of a human rod, which consists of rod opsin plus retinal.

50
Q

What is a retinal?

A

It is synthesized from vitamin A, which explains why carrots, which are rich in this vitamin, are said to be good for your eyesight.

51
Q

What is a transduction?

A

It converts light into a change in membrane potential that occurs in the photopigments of photoreceptors.

52
Q

What happens to photoreceptors in the dark? In the light?

A

In the dark, they are depolarized and constantly release glutamate into synapses with bipolar cells. In the light, less glutamate is released into synapses with bipolar cells.

53
Q

2 different responses of bipolar cells to the presence of glutamate.

A

ON center bipolar cells are hyperpolarized by glutame, while OFF center bipolar cells are depolarized.

54
Q

What is the receptive field?

A

It is the place in which a visual stimulus must be located to produce a response in the neuron.

55
Q

What happens if the neuron receives information from receptors located in the fovea?

A

Its receptive field will be at the fixation point, the point at which the eye is looking.

56
Q

What happens if the neuron receives information from photoreceptors located in the periphery of the retina?

A

Its receptive field will be located off to one side.

57
Q

3 types of eye movements to keep stimuli from the environment projecting to the retina.

A

Vergence movements, saccadic movements, and pursuit movements.

58
Q

What are vergence movements?

A

They are cooperative movements that keep both eyes fixed on the same target.

59
Q

What are saccadic movements?

A

They are the shifting of gaze abruptly from one point to another.

60
Q

What is a pursuit movement?

A

It is done by looking into an object while you move it around to make your eyes move more slowly.

61
Q

What is an optic nerve?

A

It is a bundle of axons of the retinal ganglion cells.

62
Q

What is the LGN?

A

It means dorsal lateral geniculate nucleus, which is a portion of the thalamus where optic nerves convey information to, from the retina.

63
Q

What is an optic chiasm?

A

X shaped form at the base of the brain which is formed when optic nerves join together.

64
Q

Explain the contralateral half.

A

What happens is the right hemisphere receives information from the left half of the visual field, and the left hemisphere receives information from the right.

65
Q

What is blindsight?

A

It is a phenomenon in which cortical regions are involved in conscious perception of visual stimuli are damaged, but other visual pathways that are not involved in conscious perception are intact.

Physiology of Behaviour (12 decks)

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