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Aging Essay Research Paper Aging The Different — страница 4 | Referat.ru

Aging Essay Research Paper Aging The Different — страница 4

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by telomeres become revealed and produce proteins that aid in the deterioration of tissue, characteristic of the aging process (Lafferty et al., 1996, 57). To back up this theory, researchers have found that cells that do not stop dividing, such as sperm cells and many cancer cells, do not lose telomere DNA. These cells possess an enzyme called telomerase, which maintain telomeres (Lafferty et al., 1996, 57). If this is true, then with an extra boost of telomerase, DNA may replicate many more times and in turn, we may be able to live longer. Yet instead of slowing or stopping the process of aging, this possibility may only prolong it, since it has already been accepted that damaged, not a shortage of, DNA plays a large role in aging. The Body?s Weakened Immune System During

aging, the efficiency of the immune system declines. Normally, novel antigens, foreign molecules found on the surface of viruses and bacteria, activate the production of antibodies secreted by white blood cells, or lymphocytes, called B-cells. The antigens act to neutralize the virus or bacteria, rendering it harmless. If the novel antigens are missed by the antibodies, a Aback-up@ process comes into play. Macrophage cells safeguard the body and envelope foreign antigens that they later expose to T-cells for destruction. The pieces of virus that the macrophages pick up trigger the appropriate T-cell, which in turn replicates, producing more copies of itself. These T-cells, called memory T-cells, can recognize and destroy cells infected with the virus (Ricklefs and Finch, 1995,

35). These two methods of protecting the body from invasion make up the primary immune response, and this is the component of the immune system that decreases in efficiency as we age. The secondary response is the body=s resistance against pathogens it has already met. The reason for the decline in the immune system=s efficiency is that over time, we come in contact with more viral and bacterial infections so that more of our T-cells have been stimulated, converted to memory T-cells, and therefore, used. That is, they cannot be used to fight off any new viruses or bacteria that invade the body. It is possible that the total number of T-cells is set early in life. If this is so, then as we grow older, having already fought off a number of infections, we have a smaller amount of

Aunemployed@ T-cells available to fight of infections that come our way (Ricklefs and Finch, 1995, 34). In addition to the decrease in unused T-cells, antibodies used against the body=s own proteins are occasionally made. This faulty process is common in autoimmune diseases like multiple sclerosis (Ricklefs and Finch, 1995, 36). Whereas this theory of how we age is a very practical one, it almost assumes that older people die as a result of infections, no matter how mild, because of a weakened immune systems. This is often, not so. Wear and Tear Just as machinery and other equipment gets worn down through use, so too do our organs and cells. It is almost inevitable that once our first cells have developed and our organs begin functioning, they also begin a very gradual

deterioration through use. In fact, heavy use of our organs and bodies can accelerate this deterioration we call aging (Ricklefs and Finch, 1995, 33). In typists, for example, carpal tunnel syndrome and other degenerative problems come about faster and more commonly than in those who do not exhibit such specialized use of their fingers. On the other hand, problems can also arise from lack of use. Muscle atrophy, which is noticed in the elderly is the result of a lack of muscle use (Ricklefs and Finch, 1995, 33). So assuming that moderate use of our bodies is healthy and will not promote any degenerative problems seems safe. Still, even regular, moderate use of one=s body, however long it can prevent certain problems, does not hold the body=s performance at the same level for very

long. As aging continues, a loss of elasticity from the connective tissues in various parts of the body is experienced, and muscle performance, among other things, is reduced (Ricklefs and Finch, 1995, 33). In 1900, the life expectancy in the U.S. was 47 years. It may be thought that this was the length of time the human body could withstand *wear and tear= before it Abroke down.@ Today, the life expectancy in the U.S. is about 76 years because of modern technology, and many beneficial medical breakthroughs (Lafferty et al., 1996, 55). This large increase in life expectancies does not necessarily mean that human bodies can endure heavier use, or more wear and tear, but that it takes longer for our bodies to deteriorate now than it did in previous years. At the molecular level,