That is why nervous system damage usually means life long problems. Brains and all their wiring are so arcane and complicated, even our bodies don't know how to grow more than one of them, and we often don't get it right the first time either unfortunately.

Just believe we're inside a simulation and transporters won't matter.

muscle cells too. the muscle cells you have now are the same cells you had as a kid (not entirely sure how far back it goes). they dont even divide when you gain muscle, the cells just get bigger and absorb nuclei from neighboring cells to support the extra mass. the cool thing is the nuclei stick around even if you let the muscles atrophy, so theyre forever changed by having once been big. thats probably part of why its easier to get back to muscle size youve been at before.

But what about the atoms/molecules that make up those neurons? Do they last a lifetime?

Yun Tianming: am I joke to you?

Yeah but we don't know if consciousness lives in the meat or in the chemistry.