瞳孔对光反射反射弧的效应器是（）
A.瞳孔开大肌
B.瞳孔括约肌
C.睫状肌
D.虹膜
E.眼睑
参考答案：B
解析：瞳孔对光反射的途径是：传入路的光反射纤维开始与视神经纤维伴行，至视交叉时也分为交叉和不交叉纤维进入，在接近外侧膝状体时，光反射纤维离开视束，经四叠体上丘臂到中脑顶盖前区，终止于顶盖前核，在核内交换神经元，发出纤维，到同侧和对侧的缩瞳核。传出路为两侧的缩瞳核发出的神经纤维，随动眼神经入眼眶，止于睫状神经节，后者发出纤维入眼球止于瞳孔括约肌，引起瞳孔缩小。所以瞳孔对光反射反射弧的效应器是瞳孔括约肌。本题选B。
Driving in China I have been driving cars since I reached the pedals(踏板). In Canada you 1 16 to get a driver’s license. I 2 myself to be a very good driver. I visited China 20 years ago. I with my wife was in Shanghai to give a paper at a conference. We 3 the number of bicycles on the roads and the few cars. In Canada almost each family has one car, but it was 4 that most Chinese depended on bicycles. I 5 Shanghai and to other Chinese cities many times since then and have watched the fast changes on the roads. There are far fewer bicycles now but 6 cars. The roads are crowded, the government has been forced to limit the number of days some cars can 7 and the traffic jams are almost constant (经常的). So are the accidents. On a recent visit I saw four or five 8 within a two-week period. To get a driver’s license in Canada, you must drive, with an examiner, on real roads and in real traffic. However, in China you learn on a closed course, 9 real traffic, get a license and only then are able to drive under real roads. Driving in Canada and driving in China 10 two different experiences. In Canada there are traffic jams but they aren’t so bad. We have more traffic lights; we obey them and drivers are usually 11 , allowing other cars to cut in front of them knowing it won’t make much difference. In China, if you stop 12 another car cut in front of you will probably be there for a long time because once one car gets in, dozens of 13 will follow. I would rather 14 the bus than drive my car in downtown Shanghai and Beijing. Because it’s 15 and stronger than most things that might run into it.
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