Processes of sensation

• 1. Reception

  • Light enters the eye through the cornea
  • Then it passes through the pupil
  • The lens then focuses the light onto the retina
  • The retina contains photoreceptors- which are light-sensitive cells called rods and cones
• 2. Transduction Definition⇒ The electromagnetic energy that we know as light energy, is converted by the rods and cones into electromagnetic nerve impulses to travel along the optic nerve to the brain

  This allows the visual information to travel along the fibers of the optic nerve to the brain
• transduction:

  • Optic nerve definition⇒ the two tracts of neurons that transmit visual information from the eyes to the occipital lobes of the brain
  • photoreceptors (rods and cones) are organised into groups, and these groups form receptive fields
• Transduction:

  • Receptive fields definition ⇒ a particular region of the visual space

  when your retina identifies visual stimuli, it passes this information via rods or cones to bipolar cells, and then to the retinal ganglion cell

  • retinal ganglion cell definition ⇒ a type of neuron that is located near the surface of the retina; visual information from the photoreceptors is received by the retinal ganglion cells
• 3. Transmission

  • the next task is for the rods and cones to send the nerve impulses along the optic nerve to the primary visual cortex in the occipital lobes, at the very back of the brain where specialised receptor cells respond as the process of visual perception continues
• Photoreceptors:

  • detects visual stimuli
  • the rods (125000000 in each eye) are photoreceptors that are particularly sensitive to black and white, and we typically use these at night
  • the cones (6500000 in each eye) are involved in providing clear colour vision and rely on bright light to function
  • cones are used more than rods in daylight