21、
第二篇
high-stress may damage memory;
According to a report issued in May 1998, elderly people who have consistently high blood levels of cortisol don’t score as well on memory tests as their peers with lower levels of the stress lormone. What’s more, high levels of cortisol are also associated with shrinking of the hippocampus, a region of the brain that plays a key role in learning and memory.
The findings suggest that even cortisol levels in the normal, “healthy” range can actually accelerate brain aging.
The study results“now provide substantial evidence that long-term exposure to adrenal stress hormones may promote hippocampal aging in normal elderly humans,”write Nade Porter and Philip Landfield of the University of Kentucky in Lexington in their editorial. Cortisol is a hormone released in response to stress by the adrenal glands, which sit on top of the kidneys.
Over a 5 to 6-year period, Dr. Sonia Lupien and his colleagues measured 24-hour cortisol levels in 51 healthy volunteers, most of whom were in their 70s.
Despite wide variation in cortisol levels, the participants could be divided into three subgroups: those whose cortisol progressively increased over time and was currently high(increasing/high); those whose cortisol progressively increased over time and was currently moderate(increasing/moderate); and subjects whose cortisol decreased, but was currently moderate(decreasing/moderate).
The researchers tested the volunteers’memory on six people in the increasing/high category and five people in the decreasing/moderate group. The groups did not differ on tests of immediate memory, but the increasing/high cortisol group had other memory problems compared with those in the decreasing/moderate group.
The researchers also found that the total volume of the hippocampus in those in the increasing/high group was 14% lower than those in the decreasing/moderate group, although there were no differences in other brain regions.
The results suggest that “… brain aging can be accelerated by levels of adrenal hormones that are not generally regarded as pathological and that variation within this normal range is related to variation in the rate of brain aging,” write Porter and Landfield. “This further suggests that chronic stress may accelerate the worsening of hippocampus.”
练习：
1.The part of the brain important for a person’s learning and memory is
A) the cortisol
B) the adrenal glands
C) the stress hormones
D) the hippocampus
2.When the levels of cortisol go higher, the hippocampus is the brain may
A) become larger
B) become smaller
C) disappear completely
D) be totally damaged
3.According to the article, when people feel too worried or nervous or when they overwork,
A) the adrenal glands will produce a stress hormone
B) the kidneys will produce adrenal glands
C) the hippocampus will produce high levels of cortisol in the blood
D) the brain will work more effectively
4.It appears that when the total volume of the hippocampus becomes smaller as a result of high blood levels of cortisol, other brain regions
A) become smaller too.
B) Become larger
C) May remain the same in size
D) May be damaged
5. The research conducted by Porter and Landfield shows that
A) changes in the levels of adrenal hormones have nothing to do with brain aging
B) changes in the levels of adrenal hormones may affect brain aging
C) chronic stress may strengthen a man’s memory
D) the rate of brain aging always remains stable
标准答案： B,D,C,A,B
22、
第三篇：
Obsesity
Obesity refers to the medical condition characterized by storage of excess body fat. The human body maturally stores fat tissue under the skin and around organs and joints. Fat is critical for good health because it is a source of energy when the body lacks the energy necessary to sustain life processes, and it provides insulation and protection for internal organs. But too much fat in the body is associated with a variety of health problems.
Most physicians use the body mass index(BMI) to determine desirable weights. BMI is calculated as weight divided by height and people with a BMI of 27 or above are considerated obese.
Weight-height tables, such as those published by the Metropolitan Life Insurance Company, are also used as general measures of desirable weight ranges. These tables assign a range of weights for particular height. For example, a man of 1.8m has a desirable a range 66 to 83 kg, with an average of 75 kg. A woman who is 1.6m has a desirable range between 53 and 70 kg, with an average of 62kg.
The BMI and weight-height tables only provide rough estimates of desirable weights and scientists recognize that many other factors besides height affect weight. Weight alone may not be an indicator of fat, as in the case of a body-builder who may have a high BMI because of a high percentage of muscle tissue, which weighs more fat. Likewise, a person with a sedentary lifestyle may be within a desirable weight range but have excess fat tissue.
Obesity increases the risk of developing disease. Acorrding to some estimates, almost 70 percent of heart disease cases are linked to excess body fat, and obese people are more than twice as likely to develop high blood prssure. Obese women are at nearly twice the risk for developing breast cancer, and all obese people have an estimated 43 percent higher chance of developing colon caner. The risk of medical complications, particularly heart disease, increases when body fat is distributed around the waist, especially in the abdomen. This type of upper body fat distribution is more common in men than in women.
The social and psychological problems experienced by obese people are also formidable. Stereotypes about “fat” people are often translated into discriminatory practices in education, employment, and social relationships. The consequences of being in a world where people had better be “thin” are especially severe for women, whose appearances are often judged against an ideal of exaggerated slimness.
练习：
1.What is obesity?
A) Obesity is having fat tissue under the skin
B) Obesity is having fat tissue around organs
C) Obesity is being too fat
D) Obesity is having good health
2. If we say that “fat is critical for good health”, we mean that
A) fat people should be criticized
B) fat is very important for people to keep healty
C) people should be fat if they want to be healthy
D) having much fat in the body in the body is certainly associated with health problems
3. If a woman is 1.6m tall and weighs 49 kg, she
A) is considered within the desirable weight-height range
B) is definitely unhealthy
C) should be consideraed fat
D) should not be considered unhealthy
4. A heavy man
A) certainly has a lot of fat in him
B) usually has a sedentary lifestyle
C) certainly has a lot muscle in him
E) may have muscle tissue that weighs more than fat
5. Acorrding to this article, fat people may be
A) looked down upon by others
B) welcomed by others
C) considered severely ill
D) thought of having special problems.
标准答案： C,B,D,D,A
23、
上一页 [1] [2] [3] [4] [5] [6] 下一页
责任编辑：虫虫
