![]() Thus, the optic nerve is really a central tract, rather than a nerve, connecting two regions of the nervous system, namely, the layer of bipolar cells, and the cells of the lateral geniculate body, the latter being a visual relay station in the diencephalon (the rear portion of the forebrain). These bipolar cells connect with (4) the innermost layer of neurons, the ganglion cells and the transmitted messages are carried out of the eye along their projections, or axons, which constitute the optic nerve fibres. The changes induced in the rods and cones by light are transmitted to (3) a layer of neurons (nerve cells) called the bipolar cells. (2) Above the epithelium is the layer of rods and cones, the light-sensitive cells. ![]() In general, there are four main layers: (1) Next to the choroid is the pigment epithelium, already mentioned. Ten layers of cells in the retina can be seen microscopically. ![]() The retina is a complex nervous structure, being, in essence, an outgrowth of the forebrain. The chemical energy activates nerves that conduct the messages out of the eye into the higher regions of the brain. The retina is the part of the eye that receives the light and converts it into chemical energy. SpaceNext50 Britannica presents SpaceNext50, From the race to the Moon to space stewardship, we explore a wide range of subjects that feed our curiosity about space!.Learn about the major environmental problems facing our planet and what can be done about them! Saving Earth Britannica Presents Earth’s To-Do List for the 21st Century.Britannica Beyond We’ve created a new place where questions are at the center of learning.100 Women Britannica celebrates the centennial of the Nineteenth Amendment, highlighting suffragists and history-making politicians.COVID-19 Portal While this global health crisis continues to evolve, it can be useful to look to past pandemics to better understand how to respond today.Student Portal Britannica is the ultimate student resource for key school subjects like history, government, literature, and more.Demystified Videos In Demystified, Britannica has all the answers to your burning questions.This Time in History In these videos, find out what happened this month (or any month!) in history.#WTFact Videos In #WTFact Britannica shares some of the most bizarre facts we can find.Britannica Classics Check out these retro videos from Encyclopedia Britannica’s archives.Britannica Explains In these videos, Britannica explains a variety of topics and answers frequently asked questions.
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