题干

下列有关神经系统和神经调节的叙述中正确的是()

A:反射弧是神经系统结构和功能的基本单位

B:神经纤维静息电位的维持不需要消耗能量

C:神经纤维可支配和调节特定的腺体

D:神经递质的合成与核糖体、内质网等直接相关

上一题 下一题 0.0难度 选择题 更新时间:2019-06-09 01:39:13

答案(点此获取答案解析)

C

同类题2

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         A sunflower is a sunflower. A mobile phone is a mobile phone. But can you combine the two to do something for your local environment?

         As early as next year it may well be possible. When you have finished with your mobile phone you will be able to bury it in the garden or a plant pot and wait for it to flower. A biodegradable (生物可降解的) mobile phone was, this month, introduced by scientists. It is hoped that the new type of phone will encourage consumers to recycle.

        Scientists have come up with a new material over the last five years. It looks like any other plastic and can be hard or soft, and able to change shape. Overtime it can also break down into the soil without giving out any toxic (有毒的) chemicals. British researchers used the new material to develop a phone cover that contains a sunflower seed. When this new type of cover turns into waste, it forms nitrates (硝酸盐). These feed the seed and help the flower grow.

       Engineers have designed a small transparent (透明的)window to hold the seed. They have made sure it only grows when the phone is thrown away.

    “We've only put sunflower seeds into the covers so far. But we are working with plant experts to find out which flowers would perform best. Maybe we could put roses in next time,” said one scientist.

        As phone technology is developing so quickly people are constantly (经常地) throwing their mobiles away. This means manufacturers are under pressure to find ways of recycling them.

        Some 650 million mobile phones have been sold this year. Most of them will be thrown away within two years, adding plastic, heavy metal and chemical waste to the environment. A biodegradable cover can offer some relief for nature, according to the scientists.

    “The seed is released and the flower grows in the pot so you don't have to concern yourself with the phone when you have finished using it,” said Kerry Kirwan. She leads the research team, which is based at the University of Warwick in Britain.

同类题3

阅读下面文字,完成下列小题。

孤独的守望

方爱华

    在穿越了一条条宽阔马路,躲过来来往往的车辆以及川流不息的人群,准备走进那座高楼大厦的时候,却忽然被不知藏在什么地方的孤独感袭击。于是,我飞离城市,开始找寻那些遗失在远处的疼痛或者温柔,来到那个只有十几户人家的小山村。

    转过一道山梁,又穿过一道峡谷,眼前豁然开朗。那是一种惊诧!仿佛一下子掉进了一幅最浓艳的油画里。一朵秋阳,斜挂山腰,被染红的山风成了最随心的画家。一笔画山,山披灿烂,一笔描水,水放金光,一笔泼在山沟里,沟里成了五彩的天堂。

    拨开路边密密麻麻鲜嫩的细叶,下面,竟藏有一弯清溪。凝神敛息,闭目细听,一股山泉之清凉,潺潺之清音,朗朗之清虹,刹那间沁过心田,直达肺腑,更是说不出的爽朗。寻着水声一路走来,水却似多羞的少女般犹抱琵琶半遮面,一会被浓阴掩翠,一会儿环佩叮当,一会儿弯成一枚碧玉,一会儿又不知躲藏到哪里去了。细看那水宁静之极,无波无痕,柔润如美玉。那是谁家的女儿?押着唐韵,携着汉风,一点点地走近,走近,将心清凉成一片温润的水域。

    这是一个真正意义上的“世外桃源”,是在尘世苦苦寻求而不得的心灵的栖息地

    我在进入小村的那一瞬,突然变得很宁静。我用了很大的努力,才从这幅静默的油画中走出来,一路跋山涉水而来的疲倦和烦躁一扫而光。一处处低矮的农舍以最简单的装束站立在我面前,而它后面是五彩锦缎装扮起来的山坡,像一首天地之间的赞歌,我看见纯朴与艳丽和谐的统一。

    田园,多么美妙的字眼,它让许许多多流浪的心灵找到了家的温暖。袅娜的炊烟,鸡鸣狗叫,满山遍野的牛羊,子孙绕膝,我多么希望看到曾经在这里上演过的那些温暖和最原始的一幕幕生活图景啊。然而这里拥有的除了安静还是安静。看不见炊烟,听不见鸟语,也听不见动物的欢鸣,就连风都停驻在不知什么名字的山那边。

    物竞天择,时代犹如一列火车,轰鸣着滚滚向前。贫困终被繁华取代,宁静总被喧哗掩盖,那些没了主人的房屋,虚掩的房门,荒凉的院落,都似在诉说着一种久已淡去的生活,房前屋后的柿子树上,挂满红艳艳的小灯笼,就连地上也落了许多熟透的柿子。这些原本代表丰收的累累果实,在这里忽然受到冷落。

    一方石碾,丰碑一样默默地站在时光的怀抱里。深深的皱纹里记载着多少酸甜苦辣的过往?它在怀念那些五谷丰登的日子吧,还有那吱吱唱着的远去的歌谣。我看见空地上面的水井里面装满了生活的百般滋味。

    所有的土地都荒芜着,那些被收割的玉米秸杆,怀抱成一堆坐在秋阳里,哀伤而无助。曾几何时啊,仿佛还看到它们挺拔着腰杆,向上生长着浓浓的丰收和喜悦。一些被开垦的梯田就那么闲散敞着怀,留着斑驳的印记,像是刻满了主人点滴的心事。几垄白菜,几颗萝卜成了这些被弃置土地的最后守望者。

    我停下探访的脚步,对着一片宁静和绚丽沉默。

    我不知道繁华在身后隐退的时候,是不是一些东西也会随之消失。一个名不见经传的村庄就这样被遗弃在远离尘世的地方,在时光的隧道里独自演绎着一场兴衰与荣辱。美丽与孤独同在,寂寞与哀愁共存。

    在村庄的深处,终于见到了真正的主人。一位老人,就那么安然地倚在门口,身后巴掌大的小院里,两棵参天的老槐,像硕大的两把巨伞,卫士一样的护着庭院。树是老人出生时爷爷种下的。

    老人手捧山里红,热情地招待我们这些远方来的客人,她说家里没什么好吃的,只有这些山里的果子。问她为什么不和儿女一起走,老人只憨憨地一笑:“舍不得啊,几十年的家!”

    已是夕阳西下,那些山、那些树、那些落寞的房屋都开始变得暗淡起来。我最后一次回望山村的时候,老人正被金色笼罩,仿佛坐在一片灯影里。

    她在守望着一个人的山水,守望着一个她自己的家么?

(选自《散文百家》2010年第2期,有删改)