retina

Examples of retina in the following topics:

• Anatomy of the Eye

  • However, light does not enter the retina unaltered; it must first pass through other layers that process it so that it can be interpreted by the retina .
  • Presbyopia occurs because the image focuses behind the retina.
  • (b) A blowup shows the layers of the retina.
  • The retina contains photoreceptive cells.
  • Rods and cones are photoreceptors in the retina.

• Convergent Evolution

  • There is, however, one subtle difference: the cephalopod eye is "wired" in the opposite direction, with blood and nerve vessels entering from the back of the retina, rather than the front as in vertebrates .
  • In the vertebrate version the nerve fibers pass in front of the retina, and there is a blind spot (4) where the nerves pass through the retina.
  • In the octopus version, the eye is constructed the "right way out," with the nerves attached to the rear of the retina.

• Transduction of Light

  • Light is tranduced in rods and cones; visual information is processed in the retina before entering the brain.
  • A large degree of processing of visual information occurs in the retina itself, before visual information is sent to the brain.
  • Photoreceptors in the retina continuously undergo tonic activity.
  • Exposure of the retina to light hyperpolarizes the rods and cones, removing the inhibition of their bipolar cells.

• Visual Processing

  • Another important visual route is a pathway from the retina to the superior colliculus in the midbrain, where eye movements are coordinated and integrated with auditory information.
  • Finally, there is the pathway from the retina to the suprachiasmatic nucleus (SCN) of the hypothalamus.

• Neurons

  • Neurons usually have one or two axons, but some neurons, like amacrine cells in the retina, do not contain any axons.