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Biology 30 > Photoreception -12.2 > Flashcards

Photoreception -12.2 Flashcards

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1
Q

What is the percentage of how much vision supplies the sensory information reaching the brain?

A

80 to 90%

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2
Q

Describe the human eye.

A

fluid filled hallow ball - 2.5cm in diameter

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3
Q

How many layers does each eye have and what are they?

A

Three layers

Outer layer - sclera
Intermediate layer - choroid layer
Inner layer - retina

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4
Q

What does the cornea do?

A

It bends light rays into the eye

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5
Q

What does the choroid do?

A

Absorbs scattered light and contains blood vessels

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6
Q

What does the pupil do?

A

It is the opening for light to enter the inner eye?

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7
Q

What does the iris do?

A

It regulates the amount of light that enters the pupil
- adjusts size of pupil depending on light conditions (adaptation)

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8
Q

What do ciliary muscles do?

A

They change the shape of the lens in order to focus

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9
Q

What does the lens do?

A

Focuses light rays on the fovea centralis.

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10
Q

What is the retina?

A

Thin layer of the eye - contains the photoreceptors - rods, cones, and the fovea centralis

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11
Q

What are rods?

A

Rods are photoreceptors - they are sensitive to dim light, and allow us to see black and white

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12
Q

What are cones?

A

Cones are photoreceptors - they are sensitive to different wave lengths of light, allow us to see different colors

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13
Q

Where are cones most concentrated in?

A

The fovea centralis.

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14
Q

How do the rods and cones send sensory information to the brain?

A

Through the optic nerve.

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15
Q

What attaches ciliary muscles to the lens?

A

The suspensory ligaments

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16
Q

What is the anterior chamber?

A

The area that is Infront of the lens

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17
Q

What is the posterior chamber?

A

The area that is behind the lens

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18
Q

What is the aqueous humour?

A

Liquidy, jelly substance

Maintains the shape of the cornea

Provides oxygen and nutrients for surrounding cells

Found in anterior chamber

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19
Q

What causes glaucoma?

A

When cells in the eye detoriates due to lack of oxygen and nutrients - can lead to blindness

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20
Q

What is the vitreous humour?

A

Liquidy, jelly substance

Found in the posterior chamber

Helps maintain the shape of the eye ball

Supports surrounding cells

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21
Q

What does the lens do?

A

They focus light onto the fovea centralis and bend light rays

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22
Q

What are the two main components of the eye that make it bend?

A

The cornea and the lens.

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23
Q

What is the advantage of lens’ being flexible?

A

It allows for finer focus when viewing objects.

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24
Q

What happens to a lens, ciliary muscles, and suspensory ligaments when an object is far away?

A

Lens becomes flat
Ciliary muscles relax
Suspensory ligaments taut

25
Q

What happens to a lens, ciliary muscles, and suspensory ligaments when an object is nearby?

A

Lens becomes more rounded
Ciliary muscles contract
Suspensory ligaments relax

26
Q

What is accomadation?

A

The ability of the lens to change shape so that it can focus images clearly on the retina

27
Q

What happens when lens’ age?

A

They become lex flexible

They become more opaque - hard for light to pass through

28
Q

What are cataracts?

A

Grey, white spots on lens’

29
Q

What is astigmatism?

A

Uneven curvature at part of the cornea

Light rays cannot bend to meet at the correct focal point

30
Q

What is 20/20 vision?

A

When people can see a size 20 letter from 20 feet

31
Q

What does it mean to be nearsighted?

A

You can see close images - you cannot see size 20 letter from 20 feet

32
Q

What is myopia?

A

Associated with nearsightedness - eye ball is elongated

Focused light falls in front of the retina - instead of on photoreceptors

33
Q

What can people with myopia do to fix this?

A

They can wear concave lenses - diverges light so it falls on the retina

Corrective laser surgery - ophthalmologist reshapes cornea

34
Q

What is hyperopia?

A

Associated with farsightedness - eyeball is to short

Can see 20 size letter from 20 feet - cannot see close objects

Light rays focus behind the retina

35
Q

How can you fix hyperopia?

A

Where convex lenses - bends light rays at a sharper angle

36
Q

When does vision begin?

A

When light is focused on the photoreceptors

37
Q

Where are rods more concentrated?

A

In the outside edges of the retina

38
Q

What is responsible for peripheral vision?

A

Rods

39
Q

Where are cones more concentrated?

A

At the fovea centralis - back and centre of retina

40
Q

Which are more sensitive to light, rods or cones?

A

Cones - require a lot of light so that the fovea centralis can produce a sharp image

Rods - can be stimulated by a simple photon of light

41
Q

What are the three types of cones?

A

Red sensing cones
Blue sensing cones
Green sensing cones

42
Q

What causes color deficiency (colour blindness)

A

Caused by lack of deficiency in particular cones (usually red and green)

43
Q

What light absorbing pigment are rods made from?

A

rhodspin

44
Q

What does rhodspin consist of?

A

retinal, vitmain A derivative, and protein opsin

45
Q

Describe how rods work to send a neural impulse to optic nerve.

A

In dark - rods release inhibitory neurotransmitters that inhibit neighboring nerve cells

When rod absorbs light - rhodspin splits into retinal and protein opsin - triggers a chain of reactions - stops the release of inhibitory neurotransmitters
- Allowing the transmission of a neural impulse to the optic nerve

46
Q

What is the pigment in cones?

A

Photospin - only reacts to certain wavelengths of light

47
Q

What are the three main layers of neurons in the retina?

A

Rod and cone layer
Bipolar cell layer
Ganglion cell layer

48
Q

What forms the optic nerve?

A

Axons from the ganglion cells

49
Q

What Lobe does the optic nerve send visual images?

A

occipital lobe

50
Q

What is the area called where the ganglion cells merge to form the optic nerve?

A

The blind spot - no photoreceptors - incapable of detecting light

51
Q

What is the complete passage for visual information starting from retina?

A

Retina - optic nerve - thalamus - occipital lobe of cerebral cortex

52
Q

What does it mean that the visual image is split in the occipital lobe?

A

Left optic tract - carries information about the right portion of the visual field

Right optic tract - carries information about the left portion of the visual field

53
Q

What does it mean that humans have front facing eyes?

A

We have binocular vision - we both eyes to collect visual information about an object

54
Q

What is the leading cause of vision loss?

A

disorders of the retina

55
Q

What is diabetic retinopathy?

A

Capillaries to retina burst - spilling blood into vitreous fluid between lens and retina

(Careful regulation of blood glucose can guard this disorder)

56
Q

What happens as a result from change in consistency of the vitreous fluid?

A

Retinal detachment - Retina becomes seperated from choroid vessels that supply it with oxygen and nutrients

57
Q

What is macular degeneration?

A

Cones are destroyed due to thickened choroid vessels - cannot function like before

Result is blurring or the development of a blind spot in central vision

58
Q
A

Biology 30 (33 decks)

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