Share AQA GCSE Biology Paper 2
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What is the pupil?
The hole in the centre where light enters
What is the iris?
A muscle that controls the diameter of the pupil and how much light enters. The coloured part of the eye.
What is the retina?
Contains receptor cells called rods and cones. These are sensitive to colour and light intensity.
What is the lens?
Focuses the light into the retina
What is the ciliary muscles and suspensory ligaments?
Control the shape of the lens
What is the optic nerve?
Carries impulses from the receptors on the retina to the brain
Why is the iris reflex needed?
To prevent light from damaging the retina.
Explain the iris reflex in very bright light.
In very bright light a reflex is triggered to make the pupil smaller. The CIRCULAR muscles CONTRACT and the RADIAL muscles RELAX.
Explain the iris reflex in dim light.
In dim light a reflex is triggered to make the pupil dilate. The CIRCULAR muscles RELAX and the RADIAL muscles CONTRACT.
Define accommodation.
Where the eye focuses light on the retina by changing the shape of the lens.
Explain how the eye focuses on something that is near to it.
The ciliary muscles contract which slacken the suspensory muscles. This causes the lens to become fat (more curved) so increases how much light is ben...
Explain how the eye focuses on something that is far away.
The ciliary muscles relax which causes the suspensory muscles to pull tight. This causes the lens to become thinner so refracts light by a smaller amo...
What is long sightedness (hypermyopia)? How is it treated?
People are unable to focus on near objects. This occurs when the lens doesn't refract the light enough or the eyeball is too short. The image is broug...
What is short sightedness (myopia)? How do you treat it?
People are unable to focus on FAR objects. This occurs when the lens is the wrong SHAPE and refracts the light too much. The image is brought into foc...
Name some of the treatments for vision defects.
Contact lenses, laser eye surgery and replacement lens surgery.
What is the brain made from?
Millions of interconnected neurones
