The eye and the brain

• Cornea is clear area of sclera which refracts light
• Iris is a muscle which alters size of the pupil, controlling amount of light entering the eye
• The lens focuses light onto the retina
• The retina contains light receptor cells
• The optic nerve carries the impulses between the retina and the brain
• The sclera is the white, tough outer layer
• The choroid is a pigmented middle layer with many blood vessels. It absorbs light to avoid reflection and nourishes the retina
• The eye has a blind spot where the optic nerve leaves the retina which lacks receptor cells
• The pupil is a small hole at the centre of the iris through which light enters
• Very bright light can cause damage to the retina so your reflexes protect it
• If there's bright light - reflexes make pupil smaller. The circular muscles contract and the radial muscles relax in turn reducing the amount of light able to enter the eye
• If there's dim light - your reflexes make pupil wider - radial muscles contract and the circular muscles relax in turn increasing the amount of light able to enter the eye
• The eye focuses the light on retina by changing th shape of the lens this is known as accommodation
• If the lens cannot refract light by the right amount they're either myopic or hyperopic
• To look at near objects ciliary muscles contact, slackening suspensory ligaments, making the lens fat and more curved, increasing amount of light refracted
• Too look at distant objects ciliary muscles relax and suspensory ligaments pull tight making the lens become thin - less curved and reducing the amount of light that is refracted
• Hyperopia is longsightedness where you are unable to focus on near objects
• Hyperopia is when the lens is the wrong shape and doesn't refract the light enough or the eyeball is too short, images are brought into focus behind the retina, to correct use glasses with convex lens
• Myopia is when the lens is the wrong shape and refracts the light too much or the eyeball is too long, images are brough into focus in front of the retina, to correct it you can use glasses with a concave lens
• Myopia is short sightedness where you're unable to focus on distant objects
• What is the cerebral cortex responsible for?

  consciousness, intelligence, memory and language
• What is the medulla responsible for?

  unconscious activities like breathing and heartbeat
• The spinal cord is responsible for what?


  reflex responses
• What is the cerebellum responsible for?

  muscle coordination
• What is the cerebellum responsible for?

  muscle coordination
• Along with the spinal cord the brain is part of the central nervous system
• The brain is made up of billions of interconnected neurones