B10

• main stimuli are: light, sound chemicals temperature changes, touch and pain
• ciliary muscles are the muscles attached to suspensory ligaments and by contracting and relaxing control position of lens so that it can focus the light
• sclera is tough, white outer layer that prevents damage to eye
• cornea is transparent area at front of sclera and lets light into the eye. the curve surface changes direction of light rays
• optic nerve are the sensory neurones that carry impulses between eye and brain
• retina is area at back of eye containing clusters of light sensitive cells, when light hits retina cells are stimulated and send impulses to brain along sensory neurones in optic nerve
• iris is made up of muscles which contract and relax to control the size of the pupil and the amount of light entering the eye
• suspensory ligament hold lens in position
• NEW TECHNOLOGY: laser eye surgery, hard or soft contact lenses and lens replacement
• in myopia, laser eye surgery is used to reduce thickness of cornea so it refracts light less strongly
• in hyperopia, laser eye surgery is used to change curve of cornea so it refracts light from nearby objects more effectively
• scientists have been able to map regions of the brain to particular functions by : studying patients with brain damage, electrically stimulating different parts of the brain, using MRI to monitor brain activity after injury or task completion