Eye
Eyes are organs that detect light and convert it into electro-chemical impulses in neurons. The simplest photoreceptor cells in conscious vision connect light to movement. In higher organisms the eye is a complex optical system which collects light from the surrounding environment, regulates its intensity through a diaphragm, focuses it through an adjustable assembly of lenses to form an image, converts this image into a set of electrical signals, and transmits these signals to the brain through complex neural pathways that connect the eye via the optic nerve to the visual cortex and other areas of the brain. Eyes with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system. Image-resolving eyes are present in molluscs, chordates and arthropods.
The simplest "eyes", such as those in microorganisms, do nothing but detect whether the surroundings are light or dark, which is sufficient for the entrainment of circadian rhythms. From more complex eyes, retinal photosensitive ganglion cells send signals along the retinohypothalamic tract to the suprachiasmatic nuclei to effect circadian adjustment.
Read more about Eye: Overview, Evolution, Types of Eye, Relationship To Life Requirements, Visual Acuity, Perception of Colors, Rods and Cones, Pigmentation
Other articles related to "eye, eyes":
... In addition to the Flying Eye Hospital, ORBIS operates permanent country offices with local partners in several countries ... projects focusing on the prevention and treatment of the regions’ most prevalent eye diseases ... to increase their capacity to provide comprehensive, affordable and sustainable eye care services over the long term ...
... The pigment molecules used in the eye are various, but can be used to define the evolutionary distance between different groups, and can also be an aid in determining which are closely ... The eyes of vertebrates usually contain cilliary cells with c-opsins, and (bilaterian) invertebrates have rhabdomeric cells in the eye with r-opsins ... in vision, and that remnants survive in the eyes ...
... At age nine, he injured his right eye while whittling a slingshot with a knife, permanently blinding him ... Haywood never had his damaged eye replaced with a glass eye when photographed, he would turn his head to show his left profile ...
... A version is an eye movement involving both eyes moving synchronously and symmetrically in the same direction ... up and left Laevodepression / gaze down and left Dextrocycloversion - top of the eye rotates to the right Laevocycloversion - top of the eye rotates to the left ...
... An eyelid is a thin fold of skin that covers and protects the eye ... The levator palpebrae superioris muscle retracts the eyelid to "open" the eye ... human eyelid features a row of eyelashes which serve to heighten the protection of the eye from dust and foreign debris, as well as from perspiration ...
Famous quotes containing the word eye:
““If the law supposes that,” said Mr. Bumble, squeezing his hat emphatically in both hands, “the law is a ass—a idiot. If that’s the eye of the law, the law is a bachelor; and the worst I wish the law is, that his eye may be opened by experience—by experience.””
—Charles Dickens (1812–1870)
“And all my days are trances,
And all my nightly dreams
Are where thy dark eye glances,
And where thy footstep gleams—
In what ethereal dances,
By what eternal streams.”
—Edgar Allan Poe (1809–1849)
“The eye repeats every day the first eulogy on things—”He saw that they were good.””
—Ralph Waldo Emerson (1803–1882)