请简述肌肉收缩的滑动模型。
参考答案:1、动作电位的产生;
2、钙离子的释放;
3、原肌球蛋白位移;
4、肌动蛋白丝与肌球蛋白丝的相对滑动;
5、钙离子的回收。
— Good morning, Grand Hotel.
— Hello, I'd like to book a room for the nights of the 18th and 19 th.
— _____.[ ]
A. What can I do for you?
B. Just a minute, please.
C. What's the matter?
D. At your service.
用密度0.6×103kg/m3的木料和密度为2.7×103kg/m3的铝制成两个实心球,它们的体积相等,则两球受重力之比为( )
A.2:9
B.9:2
C.1:2.7
D.2.7:1