I would say it is most likely skills or information. It can be broadly interpreted in it's contest. It mostly likely co-insides with your required reading terms. I encourage you to use your best judgement.
The first one, axons can send messages.
The doctor. most likely, is referring to the settling process. In this process, the muscles are still adjusting or on the process of healing so he is experiencing some back pains due to this. Once the muscles are settled in place, he would feel normal again.
