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Biology > Eye > Flashcards

Eye Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What are the 3 layers of the eye

A
  • Sclera
  • Choroid
  • Retina
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2
Q

Describe the structures and functions of the sclera

A
  • Tough, white outer covering of eyeball
  • Protects eyeball from mechanical damage
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3
Q

Describe the structures and functions of the retina

A
  • Innermost layer of eyeball
  • Contains cones and rods
  • Light-sensitive layer where images are formed
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3
Q

Describe the structures and functions of the choroid

A
  • Middle layer of eyeball between sclera and retina
  • Contains black pigments to prevent total internal reflection of light
  • Contains blood vessels that bring nutrients to eyeball and remove metabolic waste
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4
Q

Describe the structures and functions of the ciliary body

A
  • Consists of ciliary muscles
  • Controls thickness or curvature of lens
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5
Q

Describe the structures and functions of the cornea

A
  • Transparent layer in front of eye
  • Refracts light onto lens
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6
Q

Describe the structures and functions of the aqueous humour

A
  • Transparent, watery fluid
  • Refracts light onto lens
  • Keeps eyeball firm
  • Serves as a medium for diffusion of oxygen and nutrients
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6
Q

Describe the structures and functions of the iris

A
  • Consists of circular and radial muscles
  • Surrounds pupil, in front of lens
  • Adjusts amount of light entering eye by changing pupil size
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7
Q

Describe the structures and functions of the pupil

A
  • Hole in centre of iris
  • Allows light to enter the eye
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8
Q

Describe the structures and functions of the lens

A
  • Transparent, biconcave, elastic crystalline body
  • Changes curvature or thickness to refract light onto retina
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9
Q

Describe the structures and functions of the suspensory ligaments

A
  • Connective tissue attached to the lens
  • Transfers effect of ciliary muscles to the lens
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10
Q

Describe the structures and functions of the blind spot

A
  • Found over the optic nerves
  • No photoreceptors
  • Area where neurones leave the eye
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10
Q

Describe the structures and functions of the vitreous humour

A
  • Transparent, jelly-like fluid
  • Refracts light onto retina
  • Keeps eyeball firm
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11
Q

Describe the structures and functions of the fovea

A
  • Greatest concentration of cones but no rods
  • Part of retina that images are focused on
  • Gives detailed colour vision in bright light
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12
Q

Describe the structures and functions of the optic nerve

A
  • Composed of sensory neurones
  • Transmits nerve impulses from photoreceptors to brain
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13
Q

What are photoreceptors

A

Cones and rods

14
Q

What are cones

A
  • Enable us to see colour in bright light
  • Red, blue, green cones
  • Each cone contains different pigments that absorbs light of different wavelengths
  • Most concentrated at the fovea/yellow spot
  • Do not work well in dim light
15
Q

What are rods

A
  • Allow us to see black and white in dim light
  • More sensitive to light than cones
  • Contain visual purple, a light sensitive pigment
  • Requires Vitamin A for formation of visual purple
  • Lie outside the fovea
  • Visual purple is bleached when eye is exposed to bright light, hence takes awhile to adjust when light settings change
16
Q

Define accommodation

A

Accommodation is the adjustment of the lens to change curvature or thickness so that clear images at different distances can be formed on the retina

17
Q

How is accommodation achieved

A
  • Ciliary muscle movement
  • Suspensory ligaments to transfer effect of ciliary muscles onto lens
  • Lens to be elastic
18
Q

Describe how the eye focuses on a near object

A
  • Ciliary muscles contract
  • Suspensory ligaments slack
  • Lens becomes thicker and more convex, decreasing its focal length
  • Light rays from near object are brought to focus onto retina
  • Photoreceptors stimulated, so nerve impulses are produced and transmitted to brain via optic nerve
18
Q

Describe how the eye focuses on a distant object

A
  • Ciliary muscles relax
  • Suspensory ligaments become taut
  • Lens becomes thinner and longer, increasing its focal length
  • Light rays from distant object are brought to focus onto retina
  • Photoreceptors stimulated, so nerve impulses are produced and transmitted to brain via optic nerve
19
Q

Describe pupil reflex in bright light

A
  • Photoreceptors in retina detect an increase in light intensity
  • Nerve impulses are sent along sensory neurone via optic nerve to brain
  • Brain returns impulses along motor neurone to circular and radial muscles of iris
  • Circular iris muscles contract
  • Radial iris muscles relax
  • Diameter of pupil decreases, allowing less light to enter
20
Q

What reflexes does the eye have

A

Pupil reflex
- Strong light causes pupil to become smaller to protect retina
Blink reflex
- Object coming towards eye causes eyelids to close
Tearing reflex
- Dust causes increased tear flow

21
Q

Describe pupil reflex in dim light

A
  • Photoreceptors detect a decrease in light intensity
  • Nerve impulses are sent along sensory neurone via the optic nerve to the brain
  • Brain returns impulses along motor neurone to circular and radial muscles in iris
  • Circular muscles relax
  • Radial muscles contract
  • Diameter of pupil increases, allowing more light to enter

Biology (20 decks)

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