题干

在用脊蛙(去除脑保留脊髓的蛙)进行反射弧分析的实验中,破坏缩腿反射弧在左后肢的部分结构,观察双侧后肢对刺激的收缩反应,结果如下
刺激部位
反应
破坏前
破坏后
左后肢
左后肢收缩
右后肢收缩
左后肢不收缩
右后肢不收缩
右后肢
左后肢收缩
右后肢收缩
左后肢不收缩
右后肢收缩
上述结果表明,反射弧被破坏的部分可能是                                                             

A:感受器

B:感受器和传入神经

C:传入神经和效应器

D:效应器

上一题 下一题 0.0难度 选择题 更新时间:2019-06-12 07:43:32

答案(点此获取答案解析)

C

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阅读理解

D

    “Volunteering makes you look at the world differently. You see how little things can change a person's life for the better, which makes everyone a better person.” Mason, a volunteer said.

    National Volunteer Week started in 1974 and is held every April. It is a time to thank volunteers for their achievements. It is also a perfect opportunity (机会) to encourage others to take their first step toward becoming a volunteer. Making the decision to take the first step can be the biggest problem, because they often wonder if they will be able to meet the organization's expectations (期望). Some people fear not knowing anyone else in the group. Not having enough time also prevents some from sharing their abilities.

    The following tips can help if you have some of these worries.

    ★Start out slowly, don't add too much pressure. Even a few hours a month can make a big difference in someone's life.

    ★Choose an organization with the same interests and common values.

    ★Take part in a training meeting for new volunteers, even if it is not asked.

    ★Work with a veteran volunteer. He volunteered a lot, he can help you increase the confidence and completely understand the organization's expectations.

    ★Invite a friend or family member to serve. It is a good experience to volunteer with them.

    ★Finally, it is most important to enjoy the volunteer experience and to remember that not all volunteer experiences are perfect. If one experience doesn't work, don't give up and you'll surely find the right opportunity.

    Spend some time on volunteer work and you will see great changes in people's lives. As Mason discovered during his volunteer experience, “…little things can change a person's life.”