- published: 19 May 2016
- views: 195191
The human eye is an organ that reacts to light and has several purposes. As a sense organ, the mammalian eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth. The human eye can distinguish about 10 million colors.
Similar to the eyes of other mammals, the human eye's non-image-forming photosensitive ganglion cells in the retina receive light signals which affect adjustment of the size of the pupil, regulation and suppression of the hormone melatonin and entrainment of the body clock.
The eye is not shaped like a perfect sphere, rather it is a fused two-piece unit. The smaller frontal unit, transparent and more curved, called the cornea is linked to the larger white unit called the sclera. The corneal segment is typically about 8 mm (0.3 in) in radius. The sclerotic chamber constitutes the remaining five-sixths; its radius is typically about 12 mm. The cornea and sclera are connected by a ring called the limbus. The iris is the colored circular structure concentrically surrounding the center of the eye, the pupil, which appears to be black. A device known as an ophthalmoscope is used to see inside the eye.
Modern humans (Homo sapiens, primarily ssp. Homo sapiens sapiens) are the only extant members of Hominina clade (or human clade), a branch of the taxonomical tribe Hominini belonging to the family of great apes. They are characterized by erect posture and bipedal locomotion, manual dexterity and increased tool use, and a general trend toward larger, more complex brains and societies.
Early hominins—particularly the australopithecines, whose brains and anatomy are in many ways more similar to ancestral non-human apes—are less often referred to as "human" than hominins of the genus Homo. Some of the latter used fire, occupied much of Eurasia, and gave rise to anatomically modern Homo sapiens in Africa about 200,000 years ago. They began to exhibit evidence of behavioral modernity around 50,000 years ago, and migrated in successive waves to occupy all but the smallest, driest, and coldest lands.
The spread of humans and their large and increasing population has had a profound impact on large areas of the environment and millions of native species worldwide. Advantages that explain this evolutionary success include a relatively larger brain with a particularly well-developed neocortex, prefrontal cortex and temporal lobes, which enable high levels of abstract reasoning, language, problem solving, sociality, and culture through social learning. Humans use tools to a much higher degree than any other animal, are the only extant species known to build fires and cook their food, and are the only extant species to clothe themselves and create and use numerous other technologies and arts.
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.
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You will learn about "Human Eye" in this video. The human eye is one of the most valuable sense organs that enables us to see the world around us. Let us study about the different parts of an eye. Sclera is a tough outer coat that protects the entire eyeball. Choroid is a vascular layer of the eye. It contains blood vessels that nourish the inner parts of the eye. Cornea is the front portion of the eye. It is convex in shape and bulges outside. Light enters the eye through the cornea. Iris is a dark muscular diaphragm located just behind the cornea. It regulates the amount of light entering the eye by adjusting the size of the pupil. Pupil is a hole in the middle of the iris. Size of the pupil decreases or increases depending upon the intensity of light entering the eye. It is made up of a...
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We depend on our eyes more than any other sense, however many of us take this precious gift for granted. Without them, we could not experience a beautiful sunset, see the faces of our loved ones, or view the natural marvels of the world. We rely on our eyesight for so much, but most people have only a vague idea of how our eyes work. There are actually many different parts of the eye working together to form a unique self-sustaining system. Though smaller than a ping-pong ball, the eye allows us to see, while cleaning, moisturizing and disinfecting itself at the same time. Learn more at www.biotrue.com.
Class 10th Physics: Human Eye and Colourful World Image Formation on Retina. Aakash iTutor (Enquire Here: http://www.aakashitutor.com/edu-tab/) - A next generation tablet based complete educational product.
The human eye is an organ that reacts to light and has several purposes.The eye is a complex structure with layers, lens, muscles, receptors, that is surrounded by many bones.Watch various parts of our human eye illustration for descriptions of the human eye anatomy.
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http://squarespace.com/tony, coupon code 'portfolio' Cameras are designed to mimic the human eye, and at a glance, they seem to be very similar. Digging deep into the images that each create, we discover that cameras exceed the human eye in many ways--and fall very short in others.
Introduction to human eye simulations in ASAP using the BIO Toolkit. Demonstrations of the Advanced Human Eye Model (AHEM) for use with ASAP.
Important Information For All Human Eyes. Please Watch This Video.
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In this Exam Revision lesson we take a close look at Gr 12 Life Sciences questions and answers relating to the Human Eye and Ear.
A violent disorder stakes claims of it's righteousness
over the border
it feeds on those who eat up the bones of it's
casualties
the momentum of each daily cycle of "you're not me"
YOU'RE NOT ME A burn for a burn is as useless as apathy
we must make choice through action no matter the
fraction we stand for
gutting it's name and denouncing it's claims of "you're
not me"
YOU'RE NOT ME
It's in your mind Travel through time
It's in your face forgotten place
It's in your hands Forgotten lands
I'm twisting and turning
I'm buning my insides
I'm breaking on fire,
"Woe!" she cries no more, for you!
Eyes watching in the dark like a song done well or a
spell gone awry
and all the books were burned with any insight on how
to fix the wrongs back to right
gottah gather all together all of us a re running
scattered and we're pointing out that
you're not me
holding off your future dreams you'd rather scream in
fear that the not-me party is marching on
not like it's the only one
time
here
everyday for many long years people die Iraqis lacking
food and in health supplies
sanctioned by the brother with no compassion for the
other
with one outstretched hand the other rapes the land
in the name of democracy, flag of hypocrisy,
war is second nature there we're quick to turn in our
neighbor
the young have war in their eyes oh how this mighty
nation cries
"You Witch!"
"Communist"
"Pinko"