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. Then
The would-be sleeper who refights his daily battles in bed——or rehearses tomorrow’s problems——finds it hard to fall asleep. Then
admin
2009-02-10
92
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 serotonon 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 were 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 EEG’s showed the brainwave 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 brain stem is located (Paragraph 2 ) _______.
选项
A、in the hypothalamus
B、between the brain and the spinal cord
C、in the transmitter nerve cells
D、between the hypothalamus and the brain
答案
B
解析
第二段中指出“...the brain stem,which joins the brain to the top of the spinal cord...”即脑干连接brain 与 spinal cord,所以B项正确。
转载请注明原文地址:https://kaotiyun.com/show/IL6K777K
0
专业英语四级
相关试题推荐
MyprofessorbrotherandIhaveanargumentaboutheadandheart,aboutwhetherheovervaluesIQwhileIleanmoretowardEQ.We
WastheRedPlanetonceawetplanet?ApluckyMartianroverfinallydeliverssomehardevidence.GiovanniSchiaparellicould
WastheRedPlanetonceawetplanet?ApluckyMartianroverfinallydeliverssomehardevidence.GiovanniSchiaparellicould
A、Peoplewhoaretrainingtobeteachers.B、Socialworkers.C、PeoplewhoalreadyhaveaBachelor-leveldegree.D、Overseasstuden
Tobecalledbeautifulisthoughttonamesomethingessentialtowomen’scharacterandconcerns.(Incontrastbymen—whoseessen
Unlikeanyothercreatureonthisplanet,humanscanlearnandunderstand,withouthavingexperienced.Theycanthinkthemselve
Unlikeanyothercreatureonthisplanet,humanscanlearnandunderstand,withouthavingexperienced.Theycanthinkthemselve
Recentyearshaveseenanincreasingnumberofchildrenbecomingthevictimsofabuse.Fortunately,educationonsexsafetyisn
(1)ScientistssayChandraprovidesfirstevidencethattwomysteriescancoexistinonegalaxy.(2)Inaverybrightgalaxy4
______,Imustdoanotherexperiment.
随机试题
线性表常采用的两种存储结构是()。
已经按法定程序审查批准的食品产品在销售中还应到当地哪个部门注册准销
典型胃溃疡疼痛的特点是
人工流产术的术中并发症不包括
汪女土,35岁,未婚,普查发现:子宫呈均匀性增大,如孕6周,质硬光滑,活动。追问病史:月经过多4~5年,且经期延长为12天,无痛经史。初步考虑子宫肌瘤。
反映和衡量建筑用地使用强度的一项重要指标称为()。
振兴工程公司承揽了幸福住宅小区建设项目。开工前,该项目的项目经理编制工作任务分工表,首先要对各项管理任务进行()。
银行业从业人员在履行协助执行义务过程中,应该做到()。
社会变迁最根本的原因是( )。
Whatdoesthespeakermainlydiscuss?
最新回复
(
0
)