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How Vision Works

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by

Maria Acosta

on 29 September 2013

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Transcript of How Vision Works

By: Maria Acosta
How Vision Works
Sitting along the beach, you watch a boat rock back and forth.

But, how exactly does the pathway of the boat's light reflections enter your eyes, and enable you to watch the boat?
Visual Processing
The brain integrates information from many characteristics into our singular perception by means of parallel processing.
In this case, parallel processing means that your brain is able to process the boat at the sea rocking back and forth, all at the same time and combine them into a single visual sense of your environment.
VISUAL PATHWAYS
Each brain hemisphere receives information from eyes about opposite of the visual field because half of the axons of each optic nerve cross over at the optic chiasm to the opposite side the brain.
First Thing's First:
Lets take a tour of the eye!
Optic Disc
The optic nerve leaves the eye at the optic disc.
Here there are no rods or cones.
Therefore, their absence produces a "blind spot" in the visual field.
Light enters the cornea, or window of the eye. The cornea is a transparent coating over the front part of the eye and functions to protect the eyeball and to focus light into the eye.
The retina is made up of different layers of cells
Photoreceptors-cells that convert light and are located in the inner most layer.
In order to reach these receptors, light must pass through the ganglion cells and the bipolar neurons as well as the blood vessels that nourish them.

The iris is the colored part of the eye.
It optimizes the function of the eye by helping to regulate the amount of light that enters the eye.
Light passes through an opening in the iris called the pupil. In bright light the pupil becomes smaller while in dim light the pupil becomes wider and opens wider and lets more light in.
Inside the eye, light moves through the lens. The shape of the lens changes to focus on images that are closer or farther away through a process called accommodation.
To focus on an object that is close to the eyes, the muscles around the lens contract, making them rounder.
To focus on an object that is far away, such as the boat on the beach, the muscles flatten the lens, making them samller.
The lens of the eyes then focus the light on the retina.
The retina is a neural tissue lining the back of the eyeball.
Here light rays of the boat are converted into electrical impulses, which are then transmitted through the optic nerve.
The axons of ganglion cells make up the optic nerve.
The optic nerve then carries the information out through the back of the eye to the brain.
There are two kinds of receptor cells for vision: rods and cones.
Rods- involved in nighttime and dim light
Cones- sensitive to color in bright light
The rods and cones are arranged differently around the fovea, or point of sharpest vision.
The rods are distributed around the sides of the retina, while the cones are highly concentrated around the fovea. This is why in dim light it is harder to bring objects into focus, while in bright light it is easier to see things clearly, which also explains why you are able to see the boat rock back and forth.
After the rods and cones convert light into recognizable neural signals, they send the signals to bipolar cells. These then pass along the signals to the ganglion cells.
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