Flashcards · Biology · Homeostasis and 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 sclera?
The tough, white outer layer of the eye that protects it.
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How does the eye adapt to dim light?
The pupil gets larger so more light enters, and the rod cells become more sensitive.
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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 muscles 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 myopia (short sight)?
The lens is too strong or the eyeball too long, so light focuses in front of the retina.
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How is myopia (short sight) corrected?
With a concave lens.
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How is hyperopia (long sight) corrected?
With a convex lens.
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Name the part of the eye marked X and say what it does. The sclera. It is the tough, white outer layer that protects the eye and gives it its shape.
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Label the eye. 
Cornea, sclera, iris, pupil, lens, ciliary muscles, 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.