Yes, Kitt.... internal damage comes from mitochondrial failures and failure of the cell to live normally. (genetic failure)

Toxins exert this effect too, on the cell's interior. But also the myelin can be damaged from compression, stretching, or attack by temporary cytokines (inflammation agents made by the body)...and when that attack is over, it may be repaired.

Do I find the terminology used today rather confusing. I think it is a historical thing--medical terms coined in the past and continuing to be used today.