首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
The would-be sleeper who refights his daily battles in bed -- or rehearses tomorrow’s problems -- finds it hard to fall asleep.
The would-be sleeper who refights his daily battles in bed -- or rehearses tomorrow’s problems -- finds it hard to fall asleep.
admin
2013-04-22
79
问题
The would-be sleeper who refights his daily battles in bed -- or rehearses tomorrow’s problems -- finds it hard to fall asleep. Then he starts worrying about his inability to sleep, which increases his insomnia, which increases his worries, which... In a new development that may help the insomnia to break this vicious cycle, Dr. Werner P. Koella of the Worcester Foundation for the Experimental Biology has discovered a chemical in the brain that may control normal sleep.
The substance, known as serotonin, is one of a number of so-called neurohormones in the brain that researchers suspect play an important part in controlling the mind and the emotions. Such chemicals, researchers have learned, assist in transmitting nerve impulses from one nerve cell to another. Serotonin, Koella notes, is produced in particularly high concentrations in the hypothalamus, the "primitive" lower part of the brain and the brain stem, which joins the brain to the top of the spinal cord and is known to contain the centers controlling the level of transmitter substance in the brain stem and hypothalamus that regulate sleep.
In preliminary experiments, Koella found that giving serotonin to cats produced signs of sleep. Electrode leads were implanted in the cats’ brains and attached to an EEG (electroencephalogram) machine to record the brain waves; next, the serotonin was injected directly into the brain or an artery in the neck. The pupils of the animals’ eyes narrowed and the electroencephalograms showed slow waves characteristic of deep sleep within five to ten minutes.
More recently, Koella deprived cats of serotonin. The animals, again equipped with implanted electrodes, were given PCPA, a drug that blocks the formation of serotonin. They wore then placed in small compartments fitted with one-way mirrors and watched round the clock.
Normally cats sleep about 15 hours a day; but Koella’s cats, after receiving PCPA, spent about 30 minutes of each day sleeping. Most of the time, their EEGs showed the brain wave patterns of arousal. Occasionally the cats would curl up as if to go to sleep, but would soon get back on their feet to wander about. The animals showed signs of irritability and often meowed complainingly after a few days of sleep deprivation, but had normal reflexes. The effects of the PCPA wore off eight days to two weeks after administration of the drug; the cats returned to their normal sleeping patterns as serotonin levels in their brains rose again.
Koella believes that at least some types of chronic insomnia may be caused by a drop in brain-serotonin levels. The Worcester physiologist is now working on chemical ways to raise the brain’s serotonin levels and produce, in his words, "a truly physiological sleeping pill. "Synthetic sleeping pills, such as barbiturates, bring sleep, but at a price: they depress the central nervous system, reduce heart action and respiration -- and they can become habit-forming or even addictive.
In one promising experiment toward the goal of letting the body "make its own pill," Koella has found that administration of 5-hydroxytryptophan, the chemical substance from which the body derives serotonin, will quickly restore a normal sleeping pattern to cats lacking in serotonin.
The language used in this article indicates that Dr. Koella ______.
选项
A、is positive that serotonin controls sleep
B、is quite uncertain whether serotonin controls sleep
C、thinks that serotonin can’t be extracted
D、thinks that serotonin might control sleep
答案
D
解析
A项说Dr. Koella很确定serotonin能控制睡眠,这一点文中已表明是不肯定的;但B项说他十分不确定,也不能这么说;而C项说serotonin不能被提取,实验证明是可以提取的;所以应选D项,Dr.Koella认为,serotonin可能可以控制睡眠。
转载请注明原文地址:https://kaotiyun.com/show/xBQK777K
0
专业英语四级
相关试题推荐
Madewasatall,handsome22-year-oldBalinesemanwhowasinlovewithonegirlbutexpectedtomarryanother.Hisstepmotherh
Therehasbeenafairamountinthenewslatelyaboutapologies,particularlywhetherthechiefexecutivesoffinancialinstitut
Sometimesyouhavetotravelveryfartogainperspectiveonthingsinyourowncountry.Recently,ItaughtaUNICEF-sponsoredc
There’sbeenalotoftalk【C1】______aboutwhoshouldgotocollegeandwhoshouldnot.Andthe【C2】______thathaveguidedthista
Somedayastrangerwillreadyoure-mailwithoutyourpermissionorscanthewebsitesyou’vevisited.Orperhapssomeonewillca
Researchershaveestablishedthatwhenpeoplearementally【C1】______biochemicalchangesoccurinthebrainthatallowitto【C2】_
Heinvitedallhis______tojoininhisweddingparty.
Heblewoutthecandleand______hiswaytothedoor.
Almosteveryoneconsiders_____adietsometimeinhisorherlife.
随机试题
()是人脑对物体的长度、面积、体积在量方面变化的反映。
下列不属于声卡功能的是______。
保证设定的条件有哪些?
下列各项,不属于败毒散组成药物的是()
罪责刑相适应原则
计算机能直接识别的语言是()。
贷款回收是指借款人按借款合同约定的还款计划、还款方式及时、足额地偿还()。
2016年12月1日,国务院新闻办公室发表《发展权:中国的理念、实践与贡献》白皮书指出,发展是中国共产党执政兴国的第一要务,是解决中国所有问题的关键。新中国取得了举世瞩目的巨大成就,开创了人类文明发展史上()的新道路。
1984年在龙骨坡遗址发现的小种大熊猫化石,年代测定距今约180万年至248万年,是目前中国发现的最早的小种大熊猫化石,小种大熊猫被公认为是大熊猫的老祖宗。此次发现进一步证明,大熊猫不但起源于龙骨坡,而且还在长江流域进化繁衍。这段文字的中心意思是( )。
计算机中16位浮点数的表示格式如图1所示:某机器码为1110001010000000。若阶码为移码且尾数为反码,其十进制真值为(8);若阶码为移码且尾数为原码,其十进制真值为(9);若阶码为补码且尾数为反码,其十进制真值为
最新回复
(
0
)