system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5, why can’t the spinal chord and other major nerves repair themselves like blood vessels or bones?
gpt
The arrangement of cells in other tissues is not nearly as critical as it is for nerves. Neighboring blood vessel cells need only to share the load of blood pressure. If they reconnect to different cells in the same tissue, that isn’t much of a problem. Still, scarring can result in distinct changes in any sort of tissue. 

A neuron’s connections to other neurons are unique. If connected differently, an impulse that would once have caused a leg muscle fiber to contract may now cause a gland to secrete. A cold sensation may be misinterpreted as a toe reporting itself as extended. People undergoing physical therapy are retraining their nervous system to account for all of these altered and severed connections.