Eye structure & iris reflex

• What is the first part of the eye that light passes through?

  Cornea
• Why does the cornea have no blood vessels?

  Oxygen diffuses into it from the air
• What is the function of the cornea?

  It refracts light entering the eye
• What is the colored part of the eye called?

  Iris
• What does the pupil do?

  Allows light to pass into the lens
• What is the role of the lens in the eye?

  It refracts light and changes shape
• How does the lens help focus light?

  By changing its shape
• What is the retina made up of?

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

  Color and bright light
• Why do we not see color in the dark?

  Only rod cells are active in low light
• What is the fovea?


  A region full of cone cells
• What is the function of the optic nerve?

  Transmits impulses to the brain
• What happens to the pupil in bright light?

  It constricts to let in less light
• What occurs to the pupil in low light?

  It dilates to let in more light
• What are the radial muscles responsible for?


  Dilating the pupils
• What do circular muscles do?


  Surround the pupil and constrict it
• What is the purpose of the iris reflex?


  • To ensure optimum light levels enter the eye
  • Protects the retina from damage
  • Adjusts pupil size based on light intensity
• Describe the changes in pupil size in response to light intensity.

  • Bright light:
  • Circular muscles contract
  • Pupil constricts
  • Low light:
  • Radial muscles contract
  • Pupil dilates
• What are the functions of rod and cone cells?

  • Rod cells:
  • Sensitive to light
  • Allow black and white vision
  • Cone cells:
  • Sensitive to color
  • Allow color vision in bright light
• What is the role of the retina in vision?

  • Contains receptor cells (rods and cones)
  • Converts light into neural signals
  • Sends signals to the brain via the optic nerve