Neuroscience Resources for Kids

The Eye

Humans are very visual animals...we use our sense of sight tointerpret much of the world around us. What we see is called "light." However, what we see is really only a small part of the entire"electromagnetic spectrum." Humans can see only the wavelengths ofelectromagnetic radiation between about 380 and 760 nanometers...this islight. Our bodies do not have detectors for wavelengths of energy lessthan 380 or greater than 760 nanometers, so we cannot "see" other types ofenergy such as gamma or radio waves. Rattlesnakes, however, can detectelectromagnetic radiation in the infrared range and use this ability tofind prey.

Electromagnetic Spectrum

Vision
First, some specifics about the eye...the human eye isabout 2.5 cm in length and weighs about 7 grams. Light passesthrough the cornea, pupil and lens beforehitting the retina. The iris is a muscle thatcontrols the size of the pupil and therefore, the amount of light thatenters the eye. Also, the color of your eyes isdetermined by the iris.
The vitreous or vitreous humor is a clear gel that provides constantpressure to maintain the shape of the eye. The retina is thearea of the eye that contains the receptors (rods and cones) that respondto light. The receptors respond to light by generating electricalimpulses that travel out of the eye through the optic nerve to thebrain.
Six bands of muscles attach to the eyeball to control the ability of theeye to look up and down and side to side. These muscles are controlled bythree cranial nerves. Four of the muscles are controlled by the oculomotor nerve (cranial nerveIII), one muscle is controlled by the trochlear nerve (cranial nerve IV)and one muscle is controlled by the abducens nerve (cranial nerveVI.)

Parts of theEye
Structure	Function
Aqueous Humor	Clear, watery fluid found in the anteriorchamber of the eye.
Cornea	Transparent tissue covering the front of the eye.Does not have any blood vessels; does have nerves.
Iris	Circular band of muscles that controls the size ofthe pupil. The pigmentation of the iris gives "color" to the eye. Blueeyes have the least amount of pigment; brown eyes have the most.
Lens	Transparent tissue that bends light passing throughthe eye. To focus light, the lens can change shape by bending.
Pupil	Hole in the center of the eye where light passesthrough.
Retina	Layer of tissue on the back portion of the eye thatcontains cells responsive to light (photoreceptors)
Rods	Photoreceptors responsive in low light conditions.
Cones	Photoreceptors responsive to color and in brightconditions.
Vitreous Humor	Clear, jelly-like fluid found in the backportion of the eye. Maintains shape of theeye.

Take a shorton-line, interactive quiz about the eye.

Do You Wear Glasses?

Theretina

Experiments and Activities aboutVision

Hear IT!

"Cornea"

"Iris"

"Retina"

Perhaps you are now ready for a crossword puzzleabout vision.
There is a good animated demonstration from KidsHealth showing How the EyeWorks. Also, eye repair and How to FixAn Eye contain excellentinformation about the development of vision science. Or visit Optics for Kids andtake the "LightTour" to learn about light.

Did youknow?

15 million people in the United States have serious vision problems; over 500,000 people in the US are blind. Eye injuries account for 4% ofthe cases of blindness. Read more about eye safety.

Did youknow?
The word "pupil" comes from the Latin word "pupa" that means "doll."The use of the word pupil for the center of the eye may have come from theobservation that if you look into the eye of anotherperson, a small version of yourself (a "doll") will be reflected back.

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Exploring theNervous System