问题 单项选择题

关于青春期发育机制与动因,以下哪项错误

A.青春期前,下丘脑对卵巢激素的负反馈作用不敏感

B.青春期垂体对GnRH反应性增强

C.下丘脑对性腺的抑制增强

D.下丘脑的多巴胺等单胺类递质促使青春期发动

E.下丘脑中去甲肾上腺素对GnRH通路起易化作用

答案

参考答案:A

解析:青春期前下丘脑的GnRH神经元未发育成熟,下丘脑对卵巢激素的抑制作用比较敏感,GnRH的分泌很少,腺垂体促性腺激素及卵巢激素的分泌处于低水平状态。

阅读理解

The South Pole is a particular place on the earth.When people stand at the top of it looking around,they will find all directions face to north.No matter how they make their first step in which direction,they will always walk towards the north.That’s to say,only north and south exist there,neither east nor west exists.

At the top of the South Pole,any clock or watch keeps good time because all meridians(子午线) join there.All kinds of local time are completely suitable there.It is even difficult to distinguish(区别) New Year’s Eve from New Year’s Day.

The explorers and scientists from different countries always fix the time according to their own.Therefore the time by their watches was different when the people with different nationality gathered there.

The Winter Solstice(冬至日) is an important festival at the South Pole.It is always on June 21 or 22.This day is called Midwinter Festival,on which the daytime is the shortest in a year and the night the longest.All people at the South Pole extend greetings to each other and present gifts to each other.They usually give all kinds of celebrations.From that day on,the daytime will get longer day by day.

小题1:At the top of the South Pole,your watch will ________.

A.keep good time

B.be five minutes fast

C.stop

D.be ten minutes slow小题2:The Winter Solstice is an important festival ________.

A.in the world

B.at the South Pole

C.at the North Pole

D.in China小题3:On the Winter Solstice,________ is the shortest in a year.

A.the night

B.the noon

C.the morning

D.the daytime

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