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38.3 Sense of Vision -- Part 2
There are many blood vessels and a brown color in the middle of the choroid layer.
The ring-shaped ciliary body and thin, circular, muscular iris can be seen near the front of the eye.
The iris regulates the size of the opening in the eye.
A basic watery solution called anterior humor fills the compartment between the lens and the cornea.
A fluid cushion, as well as waste transport, is provided by the aqueous humor.
The Page 715 compartment contains the inner layer of the eye.
Rod cells and cone cells are found in the retina.
The rods are sensitive to light, but they don't respond to colors, so at night or in a dark room, we see only shades of gray.
There are rods in the peripheral regions of the eye.
Humans can see directly at an object because the cones are sensitive to different wavelengths of light.
The fovea centralis is where vision is most acute.
There are sensory fibers in the brain.
There are no rods or cones in the area where the nerve exits the eye.
You can detect your own blind spot by putting a dot to the right of the center on a piece of paper.
While you look straight ahead, use your right hand to move the paper slowly toward your right eye.
This is your blind spot, because the dot will disappear at one point.
Light rays are focused on the retina when we look directly at the printed letters on this page.
Light rays are bent when they are brought into focus, so the image is smaller than the object.
The image on the retina is reversed from left to right.
When the information from the eye reaches the brain, it is used to orient ourselves.
As the rays pass through the ciliary body, focusing starts at the cornea.
When we view a near object, the ciliary muscle contracts and the lens becomes more round due to its elasticity.
Close work can cause muscle fatigue known as eyestrain because it requires contraction of the ciliary muscle.
Many people need reading glasses once they reach middle age because the lens loses its ability to accommodate near objects.
The human eye is focused.
An inverted and reversed image of an object forms on the retina when light rays from each point on an object are bent by the lens.
The lens is flat when focusing on a distant object because the ciliary muscle is relaxed.
The lens accommodates when focusing on a near object because the ciliary muscle contracts.
Light is focused on the photoreceptors in the eye.
There are a lot of disks in the outer segment, and some of them are covered in a substance that reacts to light.
The inner segment has synaptic endings.
There are stacks of membranous disks in the outer segment of rods and cones.
Rhodopsin is a complex molecule that is contained in each disk.
When rhodopsin absorbs light energy, it splits, releasing opsin, which sets in motion a cascade of reactions that cause ion channels to close.
Nerve impulses go to the brain.
Rhodopsin is a visual substance in rods.
When a rod absorbs light, rhodopsin splits into opsin and retinal, leading to a cascade of reactions.
Rods are suited to night vision because they are sensitive to light and go to the visual areas of the cerebral cortexample.
Rod cells provide us with peripheral vision and perception of motion in the peripheral region of the retina.
The cones are activated by bright light and are located in the fovea centralis.
There are three different types of cones, which contain B, G, and R. There is a slight difference in the opsin structure of each pigment, which accounts for their individual absorption patterns.
Various combinations of cones are thought to be stimulated by different shades of color.
When green cones are stimulated, red cones are stimulated, and blue cones are not stimulated, the color yellow is perceived.
Some forms of color blindness are related to sex.
There are three layers of neurons in the retina.
The rod cells and cone cells are in the closest layer to the choroid.
Light must penetrate through the other cell layers before the rod and cone cells can be stimulated.
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