The Visual System

-THE-

A SYSTEM IS A COLLECTION OF

OBJECTS THAT WOULD BE COMPLETELY IRRELEVANT TO ONE OTHER HAD THEY NOT BEEN PUT TOGETHER AS A COMPLEX WHOLE

The Cornea

Light’s passage into the brain begins with the cornea. The cornea is the clear, protective film covering your pupil so you don’t accidentally stick a pencil into your eyeball and damage any necessary agents that help you see. The cornea also keeps in the vitreous (a kind of gel in your eye that helps your eyeball retain its shape) and slightly bends the light to direct it into your pupil.

Cornea

The Iris

The iris, much like the shutter of a camera lens, is the colorful part of your eye that helps diminish the amount of light that passes through your pupil. If you didn’t have an iris, then you would get too much light on a bright day and too little light on a day you find yourself sitting in a dungeon. And if you didn’t have an iris, everyone would look really boring and creepy.

Iris

The Pupil

The pupil is that little hole inside of your iris on your eyeball. The pupil is where the light comes in through. If you were to stick your finger into your eye to see if it was really a hole, though, you wouldn’t feel it because of your cornea and would only succeed in hurting yourself, so take my word for it.

Pupil

The Lens

The crystalline lens is, basically, a lens stuck inside of your eyeball. It focuses the light into your retina, just like a contact lens or pair of glasses. If your eye was a camera, then your lens would be… a lens. Sorry, but from now on it’s going to be really complicated.

Lens

The Retina

The retina is the “film of the camera”. Without the retina, you’re just an idiot pressing a button on a plastic box. The retina has three main layers: The photoreceptor layer (the layer that signals colors), the bipolar cells (the layer that transmits signals from the photoreceptors to the ganglion cells), and ganglion cells (the layer that transmits the retinal information to the midbrain).

Retina

Rods and Cones and MORE

The photoreceptor cells don’t collect information on color individually; they get information from a wide variety of photoreceptors called “rods and cones”. These rods and cones react to light, or to be exact, the absence of light. The darker it is, the more glutamate they release. After the bipolar cells transmit these signals to the ganglion cells, they can be interpreted as a whole, and then they are translated into a color. You can almost see now.

Photoreceptors Ganglion Cells

Rods and Cones and MORE

The photoreceptor cells don’t collect information on color individually; they get information from a wide variety of photoreceptors called “rods and cones”. These rods and cones react to light, or to be exact, the absence of light. The darker it is, the more glutamate they release. After the bipolar cells transmit these signals to the ganglion cells, they can be interpreted as a whole, and then they are translated into a color. You can almost see now.

Photoreceptors Ganglion Cells

The photoreceptor cells don’t collect information on color individually; they get information from a wide variety of photoreceptors called “rods and cones”. These rods and cones react to light, or to be exact, the absence of light. The darker it is, the more glutamate they release. After the bipolar cells transmit these signals to the ganglion cells, they can be interpreted as a whole, and then they are translated into a color. You can almost see now.

Rods and Cones and MORE

Photoreceptors Ganglion Cells

The photoreceptor cells don’t collect information on color individually; they get information from a wide variety of photoreceptors called “rods and cones”. These rods and cones react to light, or to be exact, the absence of light. The darker it is, the more glutamate they release. After the bipolar cells transmit these signals to the ganglion cells, they can be interpreted as a whole, and then they are translated into a color. You can almost see now.

Rods and Cones and MORE

Photoreceptors Ganglion Cells

Optic Nerves

The ganglion cells now have all the information it needs; it just needs to get somewhere. Almost every sensory instrument has axons: the connections between neurons that transmit electric impulses. The ganglion cells send impulses through their axons toward the optic nerves. An interesting fact is that the ganglion axons have to travel from the back of the retina forward to reach the optic nerves. Since this blocks part of the retina, it creates the so-called “blind spot”.

Optic Nerves

Lateral Geniculate Nucleus

The optic nerve passes through this “cerebral peduncle” to be interpreted into color, images, intensity, and brightness. It’s like going on a road trip to Spain and discovering you have a road map, tour guide, and a bottle of liquid you think is digestible but you’re not sure because it’s all in Spanish, so you stop at a gas station and get some stuff in English.

http://www.pbs.org/saf/1507/teaching/teaching.htm

Lateral Geniculate Nucleus

Everything you have ever seen has landed in this little gray nugget. Now you can see.

Congratulations.

Cortex

http://www.pbs.org/saf/1507/teaching/teaching.htm

Primary VisualCortex

SitesDuke University at Duhram (2002, January 21). Visual Systems.

    Retrieved April 12, 2010 from Web site:    http://pathology.mc.duke.edu/neuropath/nawr/sensory.html#visual

Anatomy of the Human Eyeball. Retrieved April 12, 2010 from    Emerald Coast Eye Institute Web site:    http://emeraldeye.com/eyeAnatomy.htm

Vornon, S. C., M.D. (2006). Hyper Brain Syllabus- Chapter 7.    Retrieved April 12, 2010 from University of Utah School of Medicine    , Web site:    http://library.med.utah.edu/kw/hyperbrain/syllabus/syllabus7.html

University of Utah School of Medicine (2009, August). Gross Anatomy    of the Human Eye. Retrieved April 12, 2010 from Web site:    http://webvision.med.utah.edu/anatomy.html