解释下列词语。

①消遣：____________________________                                                                                 

②俯瞰：____________________________                                                                          

③斑斓：____________________________                                                                                

④隐约可见：________________________                                                                             

⑤津津有味：________________________                                                                                    

⑥扣人心弦：________________________                                                                           

⑦栩栩如生：________________________                                                                             

⑧彻夜难眠：________________________                                                                           

⑨不得而知：________________________                                                                            

⑩充塞：____________________________                                                                                     

⑩纹丝不动：________________________                                                                          

⑩大惊小怪：________________________                                                                                 

下图甲是缩手反射的相关结构，图乙是图甲中某一结构的亚显微结构模式图，图丙表示三个神经元及其联系，据图回答下列问题：

缩手反射时，图乙中兴奋从A传到B的信号物质是（），由B上的“受体”与相应信号物质结合，引起B细胞产生（），使B的电位发生变化。