题目

A 90-year-old tortoise (乌龟) is going twice its usual speed after being equipped (装备) with a set of wheels. The animal, called Mrs T, was facing a terrible future after losing her two front legs in a mouse attack while she was sleeping in winter, but her owners glued the wheels onto her shell (外壳).“She’s going double the speed she used to,” said the owner Jude Ryder, “She uses her back legs to push herself along and seems quite happy.”The 58-year-old owner was surprised when she went to check on her loved pet last month and found her front legs had been eaten in the mouse 下丘脑存在着对体温变化敏感的神经元（分别称为热敏神经元和冷敏神经元），它们放电的频率可随着机体体温的升降而变化。科学家将微探头埋植在狗的下丘脑，通过向探头中灌水改变灌流液温度来改变下丘脑温度，测量A、B两个下丘脑神经元对局部温度变化的反应，得到结果如图。请回答：（1）当下丘脑中的神经元受到温度变化刺激产生神经冲动时，神经元细胞膜外的电位变化是__________。（2）据图分析，当下丘脑温度降低时，__________（填字母）神经元单位时间内的__________，故该神经元为冷敏神经元。（3）另有实验发现，若下丘脑前部受损，机体就会失去在炎热环境中调节体温的功能，表现为__________等主要散热途径失控，这说明下丘脑的该区域主要分布的是__________（填“热敏”或“冷敏”神经元）。（4）在饮水过多的情况下，细胞外液渗透压降低，位于__________的渗透压感受器产生兴奋，并将兴奋传到位于__________的水平衡调节中枢，再通过刺激垂体__________抗利尿激素，最终调节并维持水盐平衡。（5）除了神经—体液调节以外，人体维持内环境稳态的主要调节机制还有免疫调节。免疫调节是依靠由__________组成的免疫系统来实现的。