What´s the Retina Made Of?
The retina is a special type of light-sensitive tissue located ∈ the interior of the eye that's so analogous to brain tissue it's considered a part of the central nervous system. If you consider our eyes to be cameras, then the retina is the film. However, the retina does much more than just send a 'picture' to the brain – it actually has to compress the image so that it can be conveyed via the optic nerve, because the photorecep-tors ∈ the retina can take ∈ more information than the optic nerve can convey.
Although it looks like a single layer, the retina is actually very complex and comprises ten layers of nerve cells, all of which are connected by synapses. Within each of these layers are several different types of cells: the photoreceptors called rods and cones, pho-tosensitive ganglion cells, bipolar cells and other cells that assist with regulating light input as well as processing and transmitting images. Rods and cones each have their own function. Rods are more sensitive to light and are responsible for night vision and peripheral vision; each one can respond to a single photon, or particle, of light. Cones, on the other hand, work ∈ bright light and are responsible for seeing colour, fine detail and rapid movements.
Until the Nineties, it was thought that only rods and cones were involved ∈ sight. Then researchers discovered a much rarer type of cell called photosensitive ganglion cells. These cells help regulate pupil size and the light/dark cycle, or circadian rhythms, that we func-tion by.
Light reaches the rods and cones by first passing through transparent layers of nerve cells. When it reaches these photoreceptors, the light causes chemical changes ∈ both the rods and cones. The raw data is then sent back through the layers of nerve cells, which process and encode the image before sending it via the optic nerve to the brain.
Fonte: How It Works Book of Amazing Answers to Curious Questions Volume 2 © 2012 Imagine Publishing Ltd (with adaptations).
The word convey highlighted ∈ the first paragraph is closest ∈ meaning to:
