Coordination & Response

• The eye :

  • sclera
  • choroid
  • retina
  • optic nerve
  • fovea
  • cornea
  • pupil
  • iris
  • lens
  • suspensory ligament
  • aqueous humour
  • vitreous humour
• Cornea:

  • It refracts light and protects the eye
• Iris :

  • controls how much light enters the pupil
• Lens :

  focuses light onto the retina
• Optic Nerve :

  • Bundle of sensory neurones that carry impulses to the brain
• Retina :

  layer of tissue at the back of the eye that contains light receptor cells (rods and cones)
• Fovea :

  Area of the retina with highest concentration of cone cells that provides sharp vision.
• Aqueous Humour :

  • maintains the pressure in the eye and nourishes the cornea
• Vitreous Humour :

  • maintains the shape of the eye and attaches to the retina
• Ciliary muscles :

  Help change the shape of the lens in accommodation
• Sclera :

  • Tough outer layer that the muscles that move the eyeball attach to
• Pupil :

  • hole in the center of the eye that lets light in
• The iris reflex :

  bright light : smaller pupil

  • circular muscles contract
  • radial muscles relax
  • pupils constrict

  dim light : larger pupil

  • circular muscles relax
  • radial muscles contract
  • pupils dilate
• dim light :

  • circular muscles relax
  • radial muscles contract
  • pupils dilate
• bright light : smaller pupil

  • circular muscles contract
  • radial muscles relax
  • pupils constrict
• Focussing light is called accommodation
• Accommodation is controlled by the ciliary muscles and the suspensory ligaments
• Focusing on a distant object :

  • ciliary muscles relax
  • suspensory ligaments tighten
  • lens is pulled thin
• Focusing on a close object :

  • ciliary muscles contract
  • suspensory ligaments slacken
  • lens becomes fatter