问题 单项选择题

下列有关同一细胞兴奋传导的叙述,哪一项是错误的A.动作电位可沿细胞膜传导到整个细胞

B.传导方式是通过产生局部电流刺激未兴奋部位,使之出现动作电位

C.有髓纤维的跳跃传导速度与直径成正比

D.有髓纤维传导动作电位的速度比无髓纤维快

E.动作电位的幅度随直径增加而降低

答案

参考答案:E

解析:

常见错误是忽略了题干要求的是哪一项是错误的,而将正确选项选人。动作电位的传导,实际是已兴奋的膜部分通过局部电流"刺激"了未兴奋部分,使之出现动作电位,就像外加刺激在最初的受刺激部分引起动作电位一样;这样的过程在膜表面连续进行下去,就表现为兴奋在整个细胞的传导。

有髓纤维只在朗飞结处轴突膜才能和细胞外液接触,局部电流只能发生在相邻的朗飞结之间,其兴奋呈跳跃式传导,这种传导速度比无髓纤维或一般细胞的传导速度要快得多。有髓纤维的传导速度与直径呈正比。在同一细胞,动作电位具有"全或无"的特点,其幅度不随直径的增加而降低。

注意是同一细胞,故其幅度不随直径的增加而降低。

阅读理解

Andrew Carneigie, known as the King of Steel, built the steel industry in the United States, and, in the process, became one of the wealthiest men in America. His success resulted partly from his ability to sell the product and partly from his policy of expanding during periods of economic decline, when most of his competitors were reducing their investments. Carnegie believed that individuals should progress through hard work, but he also felt strongly that the wealthy should use their fortunes for the benefit of society. He opposed charity, preferring instead to provide educational opportunities that would allow others to help themselves. “He who dies rich, dies disgraced”, he often said. Among his more noteworthy contributions to society are those that bear his name, including the Carnegie Institute of Pittsburgh, which has a library, a museum of fine arts, and a museum of national history. He also founded a school of technology that is now part of Carnegie-Mellon University. Other philanthropic(慈善的) gifts are the Carnegie Endowment for International Peace to promote understanding between nations, the Carnegie Institute of Washington to fund scientific research, and Carnegie Hall to provide a center for the arts. Few Americans have been left untouched by Andrew Carnegies generosity. His contributions of more than five million dollars established 2,500 libraries in small communities throughout the country and formed the nucleus of the public library system that we all enjoy today.

小题1:The author quoted(引述) “he who dies rich, dies disgraced” in the passage to show______.

A.He felt strongly that the wealthy should use their fortunes for the benefit of society.

B.He opposed charity.

C.The wealthy die from their fortunes

D.The wealthy die from not contributing to society.小题2:Carnegie’s success includes following aspects EXCEPT_____.

A.his policy of expanding.

B.his ability to sell the product

C.his ability to produce the product

D.his hard work小题3:Which of the following may NOT be philanthropic gifts to society according to the passage?____

A.the Carnegie Institute of Washington.

B.the Carnegie Institute of Pittsburgh.

C.the steel industry.

D.the Carnegie Endowment for International Peace.小题4:What is the meaning of “Few Americans have been left untouched by Andrew Carnegie’s generosity.” in the passage?________

A.Few Americans have touched Andrew Carnegie’s generosity.

B.Many Americans have touched Andrew Carnegie’s generosity.

C.we all enjoy Andrew Carnegie’s generosity today.

D.Many Americans were given Andrew Carnegie’s generosity.

多项选择题