gcse biology eye in detail

• What does the retina have?

  contains light sensitive receptor cells, detect wavelength of light(colour) and light intensity
• What is the cornea?

  First part of eye, transparent outer layer, refracts light into eye
• What is the sclera?

  Tough supporting wall of eye
• What does the lens do?

  Focuses light onto Retina(back of eye)
• What does the iris do?

  controls amount of light entering eye
• What does the iris do in bright light?


  Circular muscles of iris contract, radial muscles relax iris constricts reducing amount of light entering eye
• What does the iris do in dim light?


  Radial muscles of iris contract, circular muscles relax pupil dilates increasing amount of light entering eye
• What does the optic nerve do?

  Carries electrical impulses from receptors on retina to brain
• What is the pupil?

  Hole in middle of iris lets light into eye
• What is the blind spot?

  Where optic nerve attaches to retina, no light sensitive receptor cells
• What does the fovea have?


  Highest concentration of light sensitive receptor cells
• What is the eye?

  sense organ that responds to changes in light
• What happens when light passes through retina?


  Receptor cells change, sends electrical impulses to brain along optic nerve
• Why is the retina very dark?


  To absorb as much light into eye
• What are the two different light sensitive cells the retina has?


  Cone cells, rod cells
• What do cone cells do?


  responds to light of certain wavelength(colour). Only work in bright light, only see colour images when light is bright enough. Cone cells are clustered in the fovea on retina. Most of light falls on retina in bright conditions.
• What are rod cells?


  Respond to difference in light intensity, more sensitive at low intensities than cone cells. Used in low light conditions. Rod cells gives images in black and white. Found all over retina