第4题: [单项选择]血钙浓度下降后多长时间内即可引起PTH分泌增加 A. <1min B. <2min C. <5min D. <10min 参考答案:A 答案解析:[考点] PTH分泌的调节 [解析] 血钙水平是调节PTH分泌的最主要因素。甲状旁腺的主细胞对低血钙极为敏感,血钙浓度的轻微下降,在1分钟内即可引起PTH分泌增加。
第8题:[单选题]44. a great ostrich egg was hung from the center of the room _____, and a corner cupboard, left open, displayed immense treasures of old silver. A.aimlessly B.absurdly C.knowingly D.evidently 参考答案:C