- published: 12 Jul 2016
- views: 3556
Eyes are the organs of vision. They detect light and convert it into electro-chemical impulses in neurons. 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 and to the pretectal area to control the pupillary light reflex.
Take me from this empty life
Mortal life of feeble cries
Open new dimensions
Grant me my new life
Let me see the darkness
Let me see the night
As a shadow
From an empty past
I shall travel through the gates of time
As a shadow
From an empty past
Stronger powers guide my final path
Open wide the sky
Split it as you fly
Lords of deepest black
Come forth through the crack
Hear my mortal calling
Questing for new life
Hear my mortal hail
From your sons of black
Hear my calling
For your mighty touch
Hear my mortal hail
Thou shall remain
As s shadow
From an empty past
Feeble falsehoods