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托福考试模拟测试题
2015年托福考试模拟测试题
Hormones in the Body
Up to the beginning of the twentieth century, the nervous system was thought to control all communication within the body and the resulting integration of behavior. Scientists had determined that nerves ran, esntially, on electrical impuls. The impuls were thought to be the engine for thought, emotion, movement, and internal process such as digestion. However, experiments by William Bayliss and Ernest Starling on the chemical cretin, which is produced in the small intestine when food enters the stomach, eventually challenged that view. From the small intestine, cretin travels through the bloodstream to the pancreas. There, it stimulates the relea of digestive chemicals. In this fashion, the intestinal cells that produce cretin ultimately regulate the production of different chemicals in a different organ, the pancreas.miss in
Such a coordination of process had been thought to require control by the nervous system; Bayliss and Starling showed that it could occur through chemicals alone. This discovery spurred Starling to coin the term hormone to refer to cretin, taking it from the Greek word hormon, meaning “to excite” or “to t in motion.” A hormone is a chemical produced by one tissue to make things happen elwhere.
As more hormones were discovered, they were categorized, primarily according to the process by which they operated on the body. Some glands (which make up the endocrine system) crete hormones directly into the bloodstream. Such glands include the thyroid and the pituitary. The exocrine system consists of organs and glands that produce substances that are ud outside the bloodstream, primarily for digestion. The pancreas is one such organ, although it cretes some chemicals into the blood and thus is also part of the endocrine system.
Much has been learned about hormones since their discovery. Some play such key roles in regulating bodily process or behavior that their abnce would cau immediate dea
th. The most abundant hormones have effects that are less obviously urgent but can be more far-reaching and difficult to track: They modify moods and affect human behavior, even some behavior we normally think of as voluntary. Hormonal systems are very intricate. Even minute amounts of the right chemicals can suppress appetite, calm aggression, and change the attitude of a parent toward a child. Certain hormones accelerate the development of the body, regulating growth and form; others may even define an individual’s personality characteristics. The quantities and proportions of hormones produced change with age, so scientists have given a great deal of study to shifts in the endocrine system over time in the hopes of alleviating ailments associated with aging.
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In fact, some hormone therapies are already very common. A combination of estrogen and progesterone has been prescribed for decades to women who want to reduce mood swings, sudden changes in body temperature, and other discomforts caud by lower natural levels of tho hormones as they enter middle age. Known as hormone replacement therapy (HRT), the treatment was also believed to prevent weakening of the
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soccerballbones. At least one study has linked HRT with a heightened risk of heart dia and certain types of cancer. HRT may also increa the likelihood that blood clots—dangerous becau they could travel through the bloodstream and block major blood vesls—will form. Some proponents of HRT have tempered their enthusiasm in the face of this new evidence, recommending it only to patients who symptoms interfere with their abilities to live normal lives.
Human growth hormone may also be given to patients who are creting abnormally low amounts on their own. Becau of the complicated effects growth hormone has on the body, such treatments are generally restricted to children who would be pathologically small in stature without it. Growth hormone affects not just physical size but also the digestion of food and the aging process. Rearchers and family physicians tend to agree that it is foolhardy to dispen it in cas in which the risks are not clearly outweighed by the benefits.
27. The word engine in the passage is clost in meaning to
(A) desire
(B) origin
(C) science海上钢琴师英语影评
(D) chemical
28. The word it in the passage refers to
(A) cretin
(B) small intestine
(C) bloodstream
acceptor(D) pancreas
29. The word spurred in the passage is clost in meaning to西域男孩的歌
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(A) remembered
