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This is a basic picture of the eye ball with the different sections labelled….

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This is a basic picture of the eye ball with the different sections labelled….

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  1. Take a look around this room. Notice how the various images and colours that you see, update constantly as you turn your head. Although the images appear to be seamless, they are in reality, constantly being updated.The quality of the images we see is only possible because human vision updates images, motion and colour on an unbelievably rapid time scale.The efficiency and completeness of your eyes and brain is unparalleled in comparison with any piece of apparatus or instrument ever invented. We know this amazing function of the eyes and brain, as the sense of vision…

  2. This is a basic picture of the eye ball with the different sections labelled….

  3. But.. That diagram is pretty complicated, so here’s a more simple version, including the three main parts of the eye..

  4. Firstly… THE IRIS.. The iris is a diaphragm of variable size, whose function is to adjust the size of the pupil to regulate the amount of light into the eye.. The iris is the coloured part of the eye, and could be blue, green, brown etc.

  5. THE PUPIL… The pupil is the aperture through which light – and hence the images we “see” and “perceive”- enters the eye. This is formed by the iris. As the size of the iris increases (or decreases), the size of the pupil decreases (or increases) correspondingly.

  6. THE SCLERA.. The sclera is tough white sheath around the outside the eye ball. This is the part of the eye that is referred to by the colloquial term “white of the eye”.

  7. Some other parts of the eye that we saw on the first diagram include.. The ciliary muscle: it’s a ring shaped muscle attached to the iris and controls contraction and relaxation of the ciliary muscle controls the shape of the lens. The lens: The lens of the eye is a flexible unit that consists of layers of tissue enclosed in a tough capsule. It is suspended from the ciliary muscle by fibres. And finally.. The optic nerve: it’s responsible for vision. Each nerve contains approx one million fibres, tansmitting information to the cells of the retina.

  8. Which leads us then on to the cells of the eye..

  9. This is a picture of the cells in the retina of the eye.. Inside these cells, there are two further cells that it comprises of.. They are the rod and the cone cell..

  10. Now you have got the general idea of the cells.. Here’s a bit more info.. These cells are divided into two sections. The bottom portion contains the nucleus and the synaptic ending (which hopefully you’ve all heard from GCSE). The synaptic ending attaches to the neurons, which produce and send signals to the brain. The upper section is made up of a membrane, which is folded into disks, and these disks absorb light.

  11. The smaller and skinnier of the two cells, the cone cell, are the colour receptors of the eye, whereas the larger and fatter rod cell, while not being sensitive to colour, is very sensitive to light. In the human eye, there are many more rod cells than there are cone cells. In animals, the number of rod and cone cells are often related to the animals instincts and habitats for example.. Nocturnal animals have high numbers of rod cells to allow them better night vision.

  12. Quiz Time!

  13. 1. Name two types of cell found in the retina.. The rod cell and the cone cell 2.Which one is the colour receptor? The cone cell is sensitive to colour 3.What is the job of the ciliary muscle? The expansion and contraction of this muscle controls the shape of the lens

  14. 4. Which part of the eye is used to gain clear images of things? The lens

  15. Finally.. We’ve thrown in some “Did You Knows” for you.. The eye muscles are the most active muscles in the whole body. By the time you turn 60, you will be exposed as much UV light as a nuclear blast. 80% of what you learn is through your eyes The eye of an ostrich is as big as its brain!

  16. It is impossible to sneeze without closing your eyes The average person blinks 12 times a minute. That’s an amazing 10, 080 blinks in a day (14 waking hours)

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