the sensory and nervous systems

the change to which your body responds is called the stimulus
1. the reaction is the response
there are five main sense organs and senses
1. ears
  1. hearing
2. eyes
  1. sight
3. nose
  1. smell
4. skin
  1. touch
5. tounge
  1. taste
the eye
1. allows us to detect light and distinguish colours
  1. to do this they have sensory cells found on the retina
    1. they change light energy into nerve impulses
      1. these nerve impulses pass from the retina to the brain along the optic nerve
        the brain then sorts out the impulses so we see things
2. the eye is made up of 3 main parts
  1. the sclera
    1. the outermost layer of the eye
    2. white in color except at the very front where it becomes transparent
    3. the transparent part is called the cornea it allows light into the eye and bends light rays
  2. the choroid
    1. middle layer of the eye
    2. its dark and has blood vessels to nourish the eye
    3. stops light bouncing around inside the eye
    4. at the front there is a ring of muscle called the iris, it is the colored part of the eye and controls the amount of light entering the eye
      1. in the middle of the iris is a hole called the pupil, light passes in through it
      2. behind the iris is the lens, it focuses light onto the retina

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