Once in awhile I pick up a book I've had for ages, that I bought long ago because it looked interesting and I thought it might be useful someday, but never actually cracked.
Lately I picked up Aging of the Autonomic Nervous System, edited by Francesco Amenta, published waaaaaaaaaay back in 1993.
(Gee, that's the year before I finally opened my first solo practice in Vancouver!)
Anyway, Chapter 2 is "The Peripheral Nerve." Given that there are 72 kilometers of this in the human body, and given that I try to treat this in people, and given that I just had a birthday and am definitely aging, it made sense to start there.
There are some very nice sections on what happens to entrapped nerves/neurons over time. In particular, section D, "The Vasa Nervorum in Aged Nerves" stands out.
We are as old as our cardiovascular system.
Read Chapter 2 here.