system
Given the following post, respond as if you're commenting on Reddit:
human
eli5- Do brain cells (Neurons) divide?
gpt
For the most part no.

They’re produced originally by a stem cell, that divides into another stem cell and a precursor cell.  That neuron precursor gets to where it needs to be and then turns itself into a neuron.  Once this specialization is complete, the neuron can’t replicate itself.

There’s a lot of production and culling of neurons when you’re an infant, and then the stem cells are mostly deactivated.  The neurons can’t replace themselves, and so the brain has very limited repair capacity.

The stem cells are deactivated so that they don’t go nuts later and grow a big tumor.  Figuring out how to *safely* reactivate them in a controlled manner is something of a holy grail in bioscience.