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The human skeleton, and in general the human body, have mechanisms that allow them to move. This movement, especially when it comes to rigid bone structures, comes thanks to something called joints. Joints, are the connection between two bone structures, and while some will allow motion because they are cushioned and movable, others will be static, depending on the function they play. In the human backbone, this is particularly necessary: both motion and protection of motion. How can this be accomplished? Through two types of joints.
In general, demifacet and facet joints are just that, joints, but while one will allow the vertebrae of the backbone to move without damaging itself and the vital spinal cord and the nerves, the others will protect from motion, or limit it.
Demifacet joints, thus, are particular in the sections of the column, T1 through T9. The name comes because it is a joint that is divided into two sections, one on the upper side of the vertebrae, and the other on the lower side, and it provides an articulation point between the vertebrae in the thoracic region of the spine and the ribs. The range of motion in this joint is very limited, only enough for the thoracic cavity to expand and close with breathing.
The Facet joints are the most common type of articulations in the vertebral column and they are full synovial joints between vertebrae that allow these bones to move in different directions, without either damaging the bodies of each bone, and protects the nerves that exit from the spina cord towards the different parts of the body. Facets can be distinguished from their position all along the column, and because they are synovial, which means, they have a cushion between them, for shock absorption.
We do not see the world in black and white; neither do we see it as two-dimensional (2-D) or flat (just height and width, no depth). Let’s look at how color vision works and how we perceive three dimensions (height, width, and depth).
Color Vision
Normal-sighted individuals have three different types of cones that mediate color vision. Each of these cone types is maximally sensitive to a slightly different wavelength of light. According to the trichromatic theory of color vision, shown in Figure 1, all colors in the spectrum can be produced by combining red, green, and blue. The three types of cones are each receptive to one of the colors.
The trichromatic theory of color vision is not the only theory—another major theory of color vision is known as the opponent-process theory. According to this theory, color is coded in opponent pairs: black-white, yellow-blue, and green-red. The basic idea is that some cells of the visual system are excited by one of the opponent colors and inhibited by the other. So, a cell that was excited by wavelengths associated with green would be inhibited by wavelengths associated with red, and vice versa. One of the implications of opponent processing is that we do not experience greenish-reds or yellowish-blues as colors. Another implication is that this leads to the experience of negative afterimages. An afterimage describes the continuation of a visual sensation after removal of the stimulus. For example, when you stare briefly at the sun and then look away from it, you may still perceive a spot of light although the stimulus (the sun) has been removed. When color is involved in the stimulus, the color pairings identified in the opponent-process theory lead to a negative afterimage. You can test this concept using the flag in Figure 2.
But these two theories—the trichromatic theory of color vision and the opponent-process theory—are not mutually exclusive. Research has shown that they just apply to different levels of the nervous system. For visual processing on the retina, trichromatic theory applies: the cones are responsive to three different wavelengths that represent red, blue, and green. But once the signal moves past the retina on its way to the brain, the cells respond in a way consistent with opponent-process theory (Land, 1959; Kaiser, 1997).
Depth Perception
Our ability to perceive spatial relationships in three-dimensional (3-D) space is known as depth perception. With depth perception, we can describe things as being in front, behind, above, below, or to the side of other things.
Our world is three-dimensional, so it makes sense that our mental representation of the world has three-dimensional properties. We use a variety of cues in a visual scene to establish our sense of depth. Some of these are binocular cues, which means that they rely on the use of both eyes. One example of a binocular depth cue is binocular disparity, the slightly different view of the world that each of our eyes receives.
A 3-D movie works on the same principle: the special glasses you wear allow the two slightly different images projected onto the screen to be seen separately by your left and your right eye.
Although we rely on binocular cues to experience depth in our 3-D world, we can also perceive depth in 2-D arrays. Think about all the paintings and photographs you have seen. Generally, you pick up on depth in these images even though the visual stimulus is 2-D. When we do this, we are relying on a number of monocular cues, or cues that require only one eye. If you think you can’t see depth with one eye, note that you don’t bump into things when using only one eye while walking—and, in fact, we have more monocular cues than binocular cues.
An example of a monocular cue would be what is known as linear perspective. Linear perspective refers to the fact that we perceive depth when we see two parallel lines that seem to converge in an image (Figure 3).
Vision is not an encapsulated system. It interacts with and depends on other sensory modalities. For example, when you move your head in one direction, your eyes reflexively move in the opposite direction to compensate, allowing you to maintain your gaze on the object that you are looking at. This reflex is called the vestibulo-ocular reflex. It is achieved by integrating information from both the visual and the vestibular system (which knows about body motion and position). You can experience this compensation quite simply.
Finally, vision is also often implicated in a blending-of-sensations phenomenon known as synesthesia.
SORRY ITS A LONG ANSWER!!!
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under the tower the D one to the right
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hope it helps
Can I be brainliest?
Explanation:
Develop a fun hobby and spend time on it every day. Manage time effectively and include time to relax. Spend less time on activites that you find difficult.
