What triggers programmed cell death in humans? Is it decided by the brain (for the entire body)? Or is it a local decision of a cell by its environment? Something else?
I realize that there might be different cases. But I'd like to get a general idea of where (and why, actually) does this happen.
As linked to by a comment below - one type of cell-death (Necrosis) just "happens" to a cell. And perhaps there are other types that are decided by the cell. What I'm asking about (and trying to understand more) is about the idea that cell-death might be initiated externally to the cell because it would be beneficial to the whole organism. Such as "the separation of fingers and toes" mentioned in Wikipedia . "Who" would initiate it? Are there examples of the CNS initiating it? Notifying the cell by nerves? By hormones? Are they initiated by neighboring cells? (And if so - what cells have the "clout" to send such signals?)
What I'm trying to understand is who decides when a cell dies in those cases where it's not the cell itself.