The eye

• What does a cross section of the eye allow us to see?

  Inside the eye's structure
• What is the first structure light meets when entering the eye?

  The cornea
• Why is the cornea transparent?

  To allow all light to pass through
• How does the cornea obtain oxygen?

  By diffusion from the outside air
• What is the function of the cornea?

  To refract or bend light
• What is the colored part of the eye called?

  The iris
• What does the iris control?

  The size of the pupil
• What is the pupil?

  A gap in the middle of the iris
• What is the role of the lens in the eye?

  To refract light and focus it
• How does the lens differ from the cornea?

  The lens can change its shape
• What does the retina contain?

  Two types of receptor cells
• What are cone cells sensitive to?

  The color of light
• Why can't we see colors in the dark?

  Only rod cells are active
• What is the fovea?

  A spot on the retina with cone cells
• What is the function of the optic nerve?

  To transmit impulses to the brain
• What happens to the pupil in bright light conditions?

  It constricts to reduce light intake
• What is the purpose of the iris reflex?

  To protect the retina from damage
• What are the two types of muscles in the iris?

  Circular and radial muscles
• How do circular muscles affect the pupil size?

  They contract to make it smaller
• What happens to radial muscles in bright light?

  They relax to allow constriction
• What occurs to the pupil in low light conditions?

  It dilates to allow more light in
• How do radial muscles affect pupil size in darkness?

  They contract to pull the pupil open
• What are the steps of the iris reflex in response to light intensity?

  • In bright light, pupils constrict
  • In low light, pupils dilate
  • Circular muscles contract in bright light
  • Radial muscles relax in bright light
  • Radial muscles contract in low light
  • Circular muscles relax in low light
• What type of organ is an eye?

  Sensory organ
• Cornea and it’s job

  Light rays pass through the transparent front of the eye

  Job- to start to focusing of the light rays
• Pupil and its job

  The light rays pass through the pupil in the centre of the iris

  Iris- the coloured part of the eye
• Lens


  The light rays pass through the lens

  Job- to focus the light rays onto the back of the eye (retina)
• Retina


  The retina contains receptor cells for light

  Receptor cells- allow us to detect light intensity and light colour
• Receptor cells


  send electrical impulses down the optic nerve to the brain
• Sclera


  This tough outer structure protects the eye
• Suspensory ligaments and suspensory muscles

  work with the lens

  Together, they allow us to focus on distant or near objects (accommodation)