问题 单项选择题

图3表示具有生物活性的蛙坐骨神经一腓肠肌标本,灵敏电流计连接在坐骨神经表面,下列叙述错误的是()。

A.电刺激①处或②处均可引起腓肠肌的收缩

B.电刺激②处,电流计指针能记录到两次电位变化

C.电刺激①处,电流计会发生反向的两次偏转

D.神经纤维上,兴奋的传导方向与膜内的电流方向相同

答案

参考答案:B

解析:电刺激传出神经或效应器都会引起收缩,腓肠肌为效应器,A正确。电刺激肌肉,因为神经和肌肉接头处相当于突触,突触问兴奋的传递是单向的,电流计不会发生偏转。B错误。电刺激神经纤维,兴奋会进行传递,神经纤维上兴奋的传递是双向的,电流计会发生两次方向相反的偏转,C正确。神经纤维上,兴奋的传导方向与膜内的电流方向相同.D正确。

阅读理解

阅读下文并回答问题。

Good afternoon! Welcome to England .  We  hope that your visit here will be a pleasant one. Now, I would like to tell you something about our laws.

The first one is about drinking. Now, you may not buy wine in the country if you are under 18 years of age, nor may your friends buy it for you.

The second one: noise. Enjoy yourselves by all means, but please don’t make unnecessary noise, especially at night. We ask you to respect other people who may wish to be quiet.

The third one: crossing the road. Be careful. The traffic moves on the left side of the road in the country. Use pedestrian crossings(人行横道) and do not take any chances when crossing the road.

My next point is about rubbish. It isn’t lawful to drop rubbish in the street. When you have something to throw away, please put it in your pocket and take it home, or put it in a dustbin.

Finally: smoking. It is against the law to buy cigarettes or tobaccos if you are under 16 years of age.

I’d like to finish by saying that if you need any kind of help, you can contact the police. The police will be pleased to help you. You can call, write or directly go to ask any policeman.

According to the passage, answer the following questions:

小题1:How many points are discussed in the speech?

_____________________________________________________

小题2:How can you contact a policeman if you need help?

_____________________________________________________

小题3:Can you buy cigarettes if you are under 16 years of age?

_____________________________________________________

选择题