Related topics: cells · brain · eye · neurons · stem cells

Fruit flies move their retinas much like humans move their eyes

Pick an object in front of you—a teacup, for example—and fix your gaze on it. You may think that you're keeping your eyes still, but you're not: Your eyes are frequently moving unbeknownst to you, making tiny involuntary ...

Fish eyes grown in a petri dish from embryonic stem cells

A research team from the Centre for Organismal Studies (COS) of Heidelberg University has demonstrated that complex retinal tissue can be cultured in a Petri dish from embryonic stem cells of bony fish. Until now, stem cells ...

How we see better by 'looking away'

When we fixate an object, its image does not appear at the place where photoreceptors are packed most densely. Instead, its position is shifted slightly nasally and upwards from the cellular peak. This is shown in a recent ...

Deep-sea vision linked to night life on the reef

To see—and survive—at night, some coral fish have developed visual adaptations that are similar to those of their cousins living in the ocean's darkest depths, new research shows.

The genetic secret of night vision

One of the most remarkable characteristics of the vertebrate eye is its retina. Surprisingly, the sensitive portions of the photoreceptor cells are found on the hind side of the retina, meaning that light needs to travel ...

page 1 from 9

Retina

The vertebrate retina is a light sensitive tissue lining the inner surface of the eye. The optics of the eye create an image of the visual world on the retina, which serves much the same function as the film in a camera. Light striking the retina initiates a cascade of chemical and electrical events that ultimately trigger nerve impulses. These are sent to various visual centers of the brain through the fibers of the optic nerve.

In vertebrate embryonic development, the retina and the optic nerve originate as outgrowths of the developing brain, so the retina is considered part of the central nervous system (CNS).. It is the only part of the CNS that can be imaged non-invasively in the living organism.

The retina is a complex, layered structure with several layers of neurons interconnected by synapses. The only neurons that are directly sensitive to light are the photoreceptor cells. These are mainly of two types: the rods and cones. Rods function mainly in dim light and provide black-and-white vision, while cones support daytime vision and the perception of colour. A third, much rarer type of photoreceptor, the photosensitive ganglion cell, is important for reflexive responses to bright daylight.

Neural signals from the rods and cones undergo complex processing by other neurons of the retina. The output takes the form of action potentials in retinal ganglion cells whose axons form the optic nerve. Several important features of visual perception can be traced to the retinal encoding and processing of light.

This text uses material from Wikipedia, licensed under CC BY-SA