Flashcards · Biology · The Nervous System
The Eye
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What does the cornea do?
It refracts light and does most of the focusing.
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What does the iris do?
It controls the amount of light entering the eye.
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What is the pupil?
The hole in the iris that lets light in.
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What does the lens do?
It changes shape to focus light on the retina.
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What does the retina contain?
Light receptor cells, rods and cones.
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What does the optic nerve do?
It carries impulses from the retina to the brain.
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What do the suspensory ligaments do?
They connect the lens to the ciliary body and hold it in place.
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What happens to the pupil in bright light?
It becomes smaller.
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What happens to the pupil in dim light?
It becomes larger.
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How does the lens change to see a near object?
The ciliary muscles contract, the ligaments slacken and the lens becomes thicker.
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How does the lens change to see a distant object?
The ciliary muscles relax, the ligaments are pulled tight and the lens becomes thinner.
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What causes short-sightedness?
The lens is too strong or the eyeball too long, so light focuses in front of the retina.
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How is short sight corrected?
With a concave lens.
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How is long sight corrected?
With a convex lens.
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What causes colour blindness?
Faulty cone cells.
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Name the part of the eye marked X and say what it does. The retina. It contains the light receptor cells, the rods and cones.
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Label the eye. 
Cornea, iris, pupil, lens, ciliary body, suspensory ligaments, retina and optic nerve.
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Describe what happens to the lens in each eye. 
Near object: the ciliary muscles contract, the ligaments slacken and the lens is thick. Distant object: the ciliary muscles relax, the ligaments are taut and the lens is thin.