the eye

• cornea

  a tough, clear covering over the iris and the pupil that protects the eye.

  light bends as it passes through this.
• retina

  the layer of light sensitive cells at the back of the eye.

  this detects images focused by the cornea and the lens.
• pupil

  a dark circle in the centre of your iris.

  its a hole that lets light into the inner eye.
• sclera

  the thick, tough, white outer covering of the eyeball.
• optic nerve

  the bundle of nerve fibres that carry information from the retina to the brain.
• iris (effector)

  a muscle that controls how much light enters the eye.
• blind spot

  the place where the optic nerve leaves the retina.

  there are no light sensitive cells here.
• lens


  a clear, flexible structure that makes an image on the eyes retina.

  it can change shape to focus on objects.
• how the eye responds to an increase in light.

  • receptor cells of the retina detects increase in light intensity.
  • electrical impulse sent along the sensory neurone in the optic nerve, to a relay neurone in the brain, to a motor neurone to the effector.
  • iris contracts and makes pupil narrower.
  • less light now reaches the retina.