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BIO 353: Advanced Human Physiology > The Visual System > Flashcards

The Visual System Flashcards

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Biology 101 flashcards
1
Q

What is sensation?

A

Bottom-up processing where sensory receptors receive and relay outside stimuli

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2
Q

What is perception?

A

Top-down processing where the brain organizes and interprets information by putting it into context. We filter out most of the sensory info we collect.

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3
Q

How can you reduce pain?

A

Drugs (NSAIDs, opioids), rub, cold, acupuncture, massage, hypnosis

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4
Q

How can Capsaicin be perceived as pain or heat?

A

Capsaicin binds to receptors causing the channel to open below 98.6 degrees and gives a sensation of heat. Prolonged activation depletes substance P (a neurotransmitter for pain/heat)

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5
Q

What is thermoreception?

A

The sence by which we perceive temperature

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6
Q

True or False. Thermoreception and pain have the same pathways.

A

True.

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7
Q

What is light?

A

Electromagnetic radiation visible to our eyes, travels in waves. This includes wavelength, frequency and amplitude.

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8
Q

Describe how the eye functions like a camera lens (visual mechanics)

A

Light enters the eyes and is focused on the retina. Retinal photoreceptors transduce light energy to electrical energy.

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9
Q

What percentage of nerve fibers are from the fovea? Where are the other nerve fibers found in the eye?

A

50%

Retina

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10
Q

What is the optic nerve?

A

Axon bundles from retina to brain

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11
Q

What is reflection?

A

Bouncing of light rays off of a surface

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12
Q

What is absorption?

A

Transfer of light energy to a particle or surface (paint)

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13
Q

What is refraction?

A

Bending of light rays from one medium to another

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14
Q

How does diabetic retinopathy effect the eyes?

A

The first stage is non-proliferative diabetic retinopathy (NPDR) and has no symptoms - 20/20 vision

It can be detected by fundus photography - microaneurysms seen (microscopic blood-filled bulges in the artery walls)

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15
Q

What are the two types of photoreceptors?

A

Rods and cones

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16
Q

Describe visual phototransduction

A

Light is converted into electrical signals in photoreceptor cells. Occurs through a photopigment (opsin) - membrane-bound protein (G protein) bound to Retinal (Vitamin A).

Causes conformational change once hit by photo - starts signal transduction cascade (channel closes)

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17
Q

What color(s) do blue cones absorb?

A

Violet and blue

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18
Q

What color(s) do rods absorb?

A

Violet, blue, green, yellow and some orange

19
Q

What color(s) do green cones absorb?

A

Blue, green, yellow and some orange

20
Q

What color(s) do red cones absorb?

A

Some blue, green, yellow, orange and red

21
Q

How does frequency impact how we see color?

A

The hue

22
Q

How does amplitude impact how we see color?

A

The brightness

23
Q

How many cones do humans have? What is this called?

A

3 types of cones; trichromats

24
Q

How is an image formed by the eye?

A

Light is refracted by the cornea. The cornea collects and bends light so it converges on the back of the eye.

25
Q

What is focal distance?

A

Distance from the reflective surface to the retina.

26
Q

What focuses light on the retina?

A

The lens

27
Q

The fovea comprises less than 1% of retinal size but takes up over _____ of the visual cortex in the brain.

A

50%

28
Q

What are some regional differences in retinal structure?

A

The central retina has more cones and greater acuity. The peripheral retina has a higher ratio of rods and cones and a higher ratio of photoreceptors to ganglion cells, and is more sensitive to light.

29
Q

Describe the visual pathway in the retina.

A

Ganglion cells –> Bipolar cells –> Photoreceptors (deepest layer, converts light into impulses)

30
Q

Why is the visual system set up “backwards”?

A

Retina contains cones to sense the colors, red, green and blue. Rods, much more light-sensitive than cones, but which are color-blind. Light travels through a mass of neurons before it reaches the light-detecting rods and cone cells. High density (very refractive) glial cells can guide light.

31
Q

What is myopia? How is this corrected?

A

A common visual defect known as near-sightedness, which occurs when the focal point falls in front of the retina

With a concave lens

32
Q

What is hyperopia? How is this corrected?

A

A common visual defect known as far-sightedness, which occurs when the focal point falls behind the retina.

With a convex lens.

33
Q

What is accommodation?

A

The process by which the eye adjusts the shape of the lens to keep objects in focus.

34
Q

What happens when the ciliary muscle is relaxed?

A

The ligaments pull on and flatten the lens.

35
Q

What happens when the ciliary muscle contracts?

A

It releases tension on the ligaments and the lens becomes more rounded.

36
Q

What is presbyopia?

A

Old eye.

It is a loss of elasticity in the lens. The cornea is less able to change shape due to the rigid and increased size of the lens.

37
Q

What is binocular vision?

A

The coordinated use of both eyes to make a single mental impression.

38
Q

What is macular degeneration?

A

Progressive destruction of macula, common eye condition in older people.

39
Q

What is retinitis pigmentosa?

A

A group of inherited diseases causing retinal degeneration (photoreceptor cells, rods and cones die )

40
Q

What is visual acuity?

A

The ability to distinguish two nearby points.

41
Q

What is a visual angle?

A

Distances across the retina described in degrees

42
Q 
Fovea
Visual Field: 
Photoreceptor: 
Functions: 
Ganglion ratio:
A

Front
Cones
Color and acuity
1:1

43
Q 
Peripheral retina
Visual field: 
Photoreceptor: 
Functions: 
Ganglion ratio:
A

Edges
Rods
Night and motion
Many: 1

BIO 353: Advanced Human Physiology (9 decks)

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