职称英语理工类补全短文练习题(7)
A And others have painful attacks all the time.
B These signals travel from nerve cells in the injured area，up the spinal cord(脊髓)to the brain，and back down again.
C It tells us that We are injured and should do something about it
D They knew little about the process of pain itself.
E The other message moves at a speed of only 013~meter a second.
F And they send the second，slower message of pain to the brain.