歷年考研英語(yǔ)閱讀理解1997年03

[00:03.69]1997 Passage3 [00:07.32]Technically, any substance other than food [00:10.48]that alters our bodily or mental functioning is a drug. [00:15.31]Many people mistakenly believe the term drug refers only [00:19.76]to some sort of medicine or an illegal chemical [00:23.05]taken by drug addicts. [00:25.47]They don't realize that familiar substances [00:28.19]such as alcohol and tobacco are also drugs. [00:32.59]This is why the more neutral term substance is now used [00:36.61]by many physicians and psychologists. [00:40.55]The phrase "substance abuse" is often used [00:43.77]instead of "drug abuse" to make clear [00:46.39]that substances such as alcohol and tobacco [00:49.93]can be just as harmfully misused as heroin and cocaine. [00:55.08]We live in a society in which the medicinal and social [00:58.60]use of substances (drugs) is pervasive: [01:02.84]an aspirin to quiet a headache, some wine to be sociable, [01:07.37]coffee to get going in the morning, [01:09.89]a cigarette for the nerves. [01:12.72]When do these socially acceptable and apparently [01:15.92]constructive uses of a substance become misuses? [01:20.25]First of all, [01:21.42]most substances taken in excess [01:23.85]will produce negative effects such as poisoning [01:27.17]or intense perceptual distortions. [01:30.60]Repeated use of a substance [01:32.42]can also lead to physical addiction or substance dependence. [01:37.36]Dependence is marked first by an increased tolerance, [01:41.38]with more and more of the substance [01:43.30]required to produce the desired effect, [01:46.83]and then by the appearance of unpleasant withdrawal symptoms [01:51.18]when the substance is discontinued. [01:54.37]Drugs (substances) that affect the central nervous system [01:59.10]and alter perception, mood, and behavior [02:03.04]are known as psychoactive substances. [02:06.16]Psychoactive substances are commonly grouped [02:09.09]according to whether they are stimulants, [02:11.41]depressants, or hallucinogens. [02:14.33]Stimulants initially speed up or activate [02:17.76]the central nervous system, [02:19.57]whereas depressants slow it down. [02:23.01]Hallucinogens have their primary effect on perception, [02:27.36]distorting and altering it in a variety of ways [02:31.60]including producing hallucinations. [02:35.32]These are the substances often called psychedelic [02:39.05](from the Greek word meaning "mind-manifesting") [02:43.80]because they seemed to radically alter [02:46.33]one's state of consciousness.

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