首页
登录
职称英语
Of 100 billion nerve cells in the human brain, how many form after birth? Fo
Of 100 billion nerve cells in the human brain, how many form after birth? Fo
游客
2023-08-22
11
管理
问题
Of 100 billion nerve cells in the human brain, how many form after birth? For years, the official answer was "zero". Scientists thought people were born with all the neurons they’d ever have. But from 1980s, biologists overturned that doctrine, finding a reservoir of stem cells that became fresh neurons in two parts of the brains of adult birds, monkeys and humans. Those discoveries were stunning, but the next seemed to top them all. In 1999, psychologist Elizabeth Gould reported large numbers of new nerve cells in a third of the monkey brain, hinting that the same part in humans — the neocortex, which lets us reason and remember — was regenerating, too. If she was right, scientists would have to revise almost all their ideas about human memory, and doctors might someday find a way to treat Alzheimer’s patients by simply turning on the neural-construction equipment.
The birth of new nerve cells, or "neurogenesis", is now confirmed in the original two parts of human brain, the hippocampus and olfactory bulb. But for the neocortex, the no-neurons theory lives — and it’s just gotten major boost.
Until December, Gould’s study stood alone and unverified. Two neuroscientists have repeated her work in Science, but not her results. Where Gould saw new nerve cells in the neocortex, Rakic and Kormack see only glial cells, the "glue" that supports neurons. But they do spot new nerve cells in the other two areas. In a January review in Nature Neuroscience, Rakic charges Gould’s work with technical problems. Focusing on what appeared to be 100 new neurons, Rakic and Kornack found that every one was merely a new glial cell hiding behind an old neuron. Gould has a cross-sectioned image from her own study that she says shows one cell marked as new — and it’s clearly a neuron. But Rakic has an answer for that, too. The method that identified the cells as "new" finds DNA synthesis, which can happen in cells that aren’t actually dividing. Rakic says Gould’s tests were too sensitive, tagging "new" neurons that weren’t. Gould responses that Rakic’s methods just weren’t sensitive enough. But even she can’t explain why that might be.
Rakic’s study squares with the idea that memory comes not from new nerve cells but from chemicals in the spaces between old ones.
Gould’s team are circulating response to Rakic and Kornack and recreating two studies side by side to see if small differences in methods are to blame. Others are also redoing the tests; a Japanese team’s unpublished results echoes Rakic’s, while another team’s support Gould’s.
Meanwhile work on less controversial new neurons marches forward. Neuroscientist Fred Gage, who’s just wrapped up a study of the function of new hippocampus nerve cells, says that’s as it should be. Still, until more studies confirm Rakic and Kornack, he’ll keep a close eye on the neocortex debate. [br] What doctrine was overturned according to the 1980’s biologists?
选项
A、The human brain contains 100 billion nerve cells.
B、The nerve cells can be generated after birth.
C、The nerve cells can’t be generated after birth.
D、The human brain has a reservoir of stem cells.
答案
C
解析
转载请注明原文地址:https://www.tihaiku.com/zcyy/2948327.html
相关试题推荐
Of100billionnervecellsinthehumanbrain,howmanyformafterbirth?Fo
Of100billionnervecellsinthehumanbrain,howmanyformafterbirth?Fo
Of100billionnervecellsinthehumanbrain,howmanyformafterbirth?Fo
Of100billionnervecellsinthehumanbrain,howmanyformafterbirth?Fo
Of100billionnervecellsinthehumanbrain,howmanyformafterbirth?Fo
WasteNot,WantNotFeedingthe9Billion:TheTragedyofW
WasteNot,WantNotFeedingthe9Billion:TheTragedyofW
WasteNot,WantNotFeedingthe9Billion:TheTragedyofW
Of100billionnervecellsinthehumanbrain,howmanyformafterbirth?Fo
Of100billionnervecellsinthehumanbrain,howmanyformafterbirth?Fo
随机试题
Aninvestigationwasmadeintotheaccident,______(在此事故中50人丧生).inwhichfiftype
UnlikesomeclassicEuropeannovels,Americanliteratureencompassesmanydiffer
对民用建筑进行防火检查时,检查人员应注意特殊场所的设置位置,下列场所或设备用房附
某日晚9:00,你突然接到一个学生电话,说晚上要请假晚些回寝,理由时自己过生日,
一般来说,影响需求变动的主要因素有()A.消费者的可支配收入
(2018年5月)下列有关短文法的表述,不正确的是( )。A.考评者以示例说明
某铜加工企业为对冲铜价上涨的风险,以3700美元/吨买入LME的11月铜期货,同
Itcannotbeusedbefore(). A.inspe
(2021年真题第1批)在执行过程中,人民法院应当裁定中止执行的情形是( )。
呕血病例: 简要病史:患者,男性,30岁,上腹隐痛不适伴反酸及胃灼热感20年,
最新回复
(
0
)