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Biology A2 Unit 1 - Physiology, Coordination And Control, And Ecosytems > Topic 5 - The Eye > Flashcards

Topic 5 - The Eye Flashcards

1
Q

What is the conjunctiva

A

Thin membrane lining the inside of the eyelids and covering the sclera

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2
Q

What is the function of the conjunctiva

A

Lubricates and protects tissues at the front of the eye, prevents foreign bodies entering the eye

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3
Q

What is the function of the sclera

A

Protects the eyeball against mechanical damage

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4
Q

What is the sclera

A

Tough outer layer that encloses the eye, except the front

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5
Q

What is the cornea

A

Transparent front part of the eye continuous with the sclera

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6
Q

What is the function of the cornea

A

Allows the passage of light while refracting it

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7
Q

What is the iris

A

The coloured part of the eye - it contains circular and radial muscles

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8
Q

What is the function of the iris

A

Controls the size of the pupil to adjust the amount of light entering the eye

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9
Q

What is the pupil

A

A gap within the iris - appears black

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10
Q

What is the function of the pupil

A

Allows light to enter the eye

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11
Q

What is the aqueous humour

A

Transparent watery fluid filling the front part of the eye

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12
Q

What is the function of the aqueous humour

A

Maintains the shape of the front chamber of the eye

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13
Q

What is the lens

A

Transparent and elastic Ovoid structure held in place behind the cornea

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14
Q

What is the function of the lens

A

Changes shape to adjust focusing of light onto the retina

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15
Q

What is the ciliary body

A

Structure which supports the lens and contains circular muscle

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16
Q

What is the function of the ciliary body

A

Contraction or relaxation of the circular muscle control the shape of the lens

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17
Q

What are suspensory ligaments

A

Strong ligaments which connect the ciliary body to the lens

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18
Q

What is the function of suspensory ligaments

A

Transfers tension in the all of the eyeball to the lens to make it thinner

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19
Q

What is the vitreous humour

A

Transparent, jelly-like material filling the rear part of the eyeball

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20
Q

What is the function of the vitreous humour

A

Maintains the shape of the rear part of the eyeball and supports the lens

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21
Q

What is the retina

A

Inner layer of the wall of the eyeball contains light-sensitive cells

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22
Q

What is the function of the retina

A

The light-sensitive cells initiate impulses in associated neurones when appropriately stimulated

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23
Q

What is the fovea

A

The region at the back of the retina that is rich in cones

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24
Q

What is the function of the fovea

A

A region with high visual activity that allows colour vision

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25
Q

What is the choroid

A

A layer of pigmented cells at the back of the eyeball behind the retina

26
Q

What is the function of the choroid

A

Contains blood vessels which supply the retina; prevents reflection of light within the eyeball

27
Q

What is the optic nerve

A

A bundle of sensory nerve fibres which leave from the back of the eye

28
Q

What is the function of the optic nerve

A

Transmits impulse from the retina to the optic centre at the back of the brain

29
Q

What is the blind spot

A

Region where optic nerve leaves inside of eyeball and so contains no light-sensitive cells

30
Q

What is the function of the blind spot

A

A region, which if light strikes it, is not sensitive to light

31
Q

What happens to the eye in bright light

A

Circular muscles contract and the radial muscles relax, making the iris widen and therefore making the pupil get narrower. The pupil is small to limit the amount of light passing through

32
Q

What happens to the eye in dim light

A

Circular muscles relax and radial muscles contract, widening the pupil to allow more light to reach the retina and provide maximal stimulation of the light-sensitive cells

33
Q

Where is light refraction adjusted to a single point on the retina

A

The lens

34
Q

What is accommodation

A

The ability to adjust focusing

35
Q

How is light accommodated to the retina from a far object

A

The ciliary muscles are relaxed, meaning pressure is transferred via the suspensory ligaments to the lens, pulling it into a thin shape

36
Q

How is light accommodated to the retina from a near object

A

The circular muscles contract, closing the aperture around the lens and releases any tension from the eyeball, meaning the lens adopts a fatter shape

37
Q

What are the two receptors to light in the retina

A

Rods and cone cells

38
Q

Where are rods and cones found

A

Cones are concentrated in the fovea at the centre of the retina
Rods are mainly found around the periphery of the retina

39
Q

What do rod cells synapse with

A

Each bipolar neurone and many bipolar cells connect with each neurone of the optic nerve

40
Q

What do cone cells synapse with

A

A single bipolar neurone and a single neurone of the optic nerve

41
Q

What is the difference in light sensitivity between rods and cones

A

Rods are sensitive to dim light
Cones are sensitive to bright light

42
Q

What is rhodopsin

A

The pigment found in rods which is composed of opsin and retinal

43
Q

What happens when light strikes rhodopsin

A

Changes occur and rhodopsin breaks down into retinal and opsin

44
Q

How is a generator potential created

A

When the membrane potential of a rod cell is changed

45
Q

What does a generator potential cause

A

A change in the membrane potential of the neighbouring bipolar neurone, with which the rod cell synapses. The bipolar cell releases transmitter substance into its synapse with a neurone of the optic nerve

46
Q

Why are rod cells sensitive

A

Because rhodopsin absorbs light readily and is more easily broken down and because retinal convergence enables the input of many rods to be added together

47
Q

Why does summation occur

A

Because generator potentials have an additive effect in stimulating bipolar neurone while transmitter substance from bipolar neurones is added to reach the threshold needed to initiate an action potential in the neurone of the optic nerve

48
Q

What is a consequence of retinal convergence

A

The brain cannot distinguish which rod of a group sharing the same optic nerve fibe has been stimulated

49
Q

What is dark adaptation

A

When almost all of the rhodopsin is entirely bleached by bright light

50
Q

What is iodopsin

A

The pigment found in cone cells

51
Q

Which is broken down more readily, Rhodopsin or Iodopsin

A

Rhodopsin

52
Q

What is high visual acuity

A

When the brain is able to distinguish between points that are close together

53
Q

Why do cones not exhibit convergence

A

As one cone associates with one neurone of the optic nerve

54
Q

What gives high visual acuity in the eye

A

Each cone cell stimulated will generate an impulse to the brain

55
Q

What are the three forms of iodopsin, and what is this theory called

A

Red, Blue and Green
This forms the basis of the trichromatic theory of colour vision

56
Q

How is pure red light broken down

A

It is broken down by red iodopsin and only the red cones will fire impulse to the brain, which is interpreted as red

57
Q

How is yellow light broken down

A

Some of the red iodopsin and some of the green iodopsin and so both red and green cones fire impules to the brain, which is interpreted as yellow

58
Q

What is colour perception dependant on

A

The relative proportions of the different types of cone that are firing impules

59
Q

Why do prey have their eyes positioned one opposite sides of their head

A

To give them a wide field to view, to facilitate the detection of potential predators

60
Q

Why do predators have eyes positioned on the front of their head

A

To use both eyes to view an object, to allow more accurate judgement of distance

61
Q

What is stereoscopic vision

A

The brain being able to create a 3D image

Biology A2 Unit 1 - Physiology, Coordination And Control, And Ecosytems (9 decks)

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