Eye, Function Flashcards

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1
Q

What does the Cornea do?

A

It refracts (Bends) light as it enters the eye

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2
Q

What does the Iris do?

A

It controls how much light enters the pupil

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3
Q

What does the Lens do?

A

It focuses light onto the retina

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4
Q

What does the Retina do?

A

It contains the light receptors

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5
Q

What does the Optic Nerve do?

A

It carries impulses between the eye and the brain

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6
Q

What do Rod Cells do?

A

They allow us to see in dimly lit areas

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7
Q

What do Cone Cells do?

A

They allow us to pick up colour

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8
Q

What is the way of remembering the function of Cone cells?

A

There are coloured cones in sport

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9
Q

How many sets of muscles are there in the Iris?

A

2

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10
Q

Which are they?

A

Circular Muscles & Radial Muscles

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11
Q

What happens to the Radial Muscle when the Circular Muscle contracts?

A

It expands

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12
Q

What happens to the Radial Muscle when the Circular Muscle relaxes?

A

It contracts

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13
Q

What happens when a pupil dilates?

A

It expands to allow more light in

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14
Q

What happens when a pupil constricts?

A

It shrinks to allow less light in

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15
Q

What happens to the eye in bright light?

A
  • Radial muscles of the iris relax.
  • Circular muscles of the iris contract.
  • Less light enters the eye through the contracted pupil.
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16
Q

What happens to the eye in dim light?

A
  • Radial muscles of the iris contract.
  • Circular muscles of the iris relax.
  • More light enters the eye through the dilated pupil.
17
Q

How do Pupil Reflexes work?

A
  • The eye controls the amount of light falling onto the retina.
  • When a receptor is stimulated, it sends a signal to the CNS, where the brain co-ordinates the response.
  • But sometimes a very quick response is needed, one that does not need the involvement of the brain.
  • Reflex actions are rapid and happen without us thinking.
18
Q

What is short sightedness?

A

Someone with short-sight can see near objects clearly, but can’t focus properly on distant objects. This is caused by the eyeball being elongated, so that the distance between the lens and the retina is too great. It can be corrected by placing a CONCAVE LENS in front of the eye.

19
Q

What is long sightedness?

A

Someone with long-sight can see distant objects clearly, but can’t focus properly on near objects. This is because the lens focuses the sharpest image behind the retina, instead of on it. This defect is often age-related, and due to a loss of elasticity in the lens. It is corrected by putting a CONVEX LENS in front of the eye.

20
Q

How do you remember which lens a short sighted person needs?

A

Concave sounds like conker, which is small.

21
Q

How do you remember which lens a long sighted person needs?

A

Someone Vexed is big and angry. Something big is usually long.

22
Q

Does a concave lens turn inwards or outwards? How do you remember?

A

The mouth of a CAVE curves INWARDS.

23
Q

Does a convex lens turn inwards or outwards? How do you remember?

A

A VEX, comes OUT to attack you.

24
Q

How do our eyes adjust to short distances?

A

For close objects, the ciliary muscles contract allowing the lens to go fat, thus bending more.

25
Q

How do our eyes adjust to long distances?

A

For distant objects, the ciliary muscles relax and the suspensory ligaments pull tight. This makes the lens pull thin - the light doesn’t.

26
Q

How does someone see?

A

Rays of light are refracted (bent) first by the cornea and then by the lens. They focus on the retina.

  • The light rays then converge towards the retina.
  • The lens is able to precisely focus the image because of its ability to change shape.
  • Focusing on a distant object, the lens becomes thinner.
    Focusing on a near object, the lens becomes fatter.
27
Q

What are Cataracts?

A
  • The lens develops cloudy patches, due to a build up of protein.
  • Over time, the patches become bigger - causing blurry, misty vision and then eventually blindness.
  • When young, our lenses are usually like clear glass, which lets us see through them.
  • Cataract surgery involves removing the clouded lens and replacing it with a clear artificial lens.
    The artificial lens is placed in the same place as your natural lens.
28
Q

How does someone focus on objects?

A

Light is focused onto the retina by refraction at the cornea, and by the lens.
The lens changes shape to make the fine adjustments needed to produce a sharp image.
This is called accommodation.
As we get older, accommodation becomes slower and weaker.

29
Q

How do vision defects work?

A
  • Short-sight and long-sight may be corrected by corneal surgery (‘laser surgery’), or by using appropriate lenses in spectacles or contact lenses.
  • In recent years laser surgery has become more popular as a way to correct eyesight.
  • The surgery usually involves reshaping the cornea – the transparent layer covering the front of the eye.
30
Q

How is colour blindness caused?

A
  • Colour blindness is inherited meaning it is passed on from the parents to their child.
  • The retina contains cells which are sensitive to either red, green or blue light.
  • People who are colour blind have a lack of receptors, or have defects in them.
    -Some people can be colourblind with only a couple of colours; red-green colour blindness is when a person has difficulty distinguishing shades of red and green.