- published: 13 May 2010
- views: 4524233
Eyes are organs that detect light and convert it into electro-chemical impulses in neurons. The simplest photoreceptors 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.[citation needed] From more complex eyes, retinal photosensitive ganglion cells send signals along the retinohypothalamic tract to the suprachiasmatic nuclei to effect circadian adjustment.
I saw an old man on the street
he was in a dumpster lookin' for somethin' to eat
he moved so slow like a dyin' dream
like a machinist who got caught in the machine
I saw this lady and she was cryin'
she said it's hard when someone you love is dyin'
I saw this kid who was about 5 years old
he was in the park all alone he was cold
there's something coming around
as wicked as it may seem
as wicked as anything could be
I know this girl she's barely alive
she's all haggard she's only twenty-five
she said she never had a friend before
I said "hey girl I'll be your friend but who's keepin' score"
I sawthis other little girl on the phone
her mother comforts her from far from home
the little girl was very hesitant
her best friend lie dead on the pavement
I always end up back on the hill
lookin' down at the landfill
I always go there when I can