system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What's happening when someone breaks their neck and dies instantly?

Sometimes I hear about a broken neck causing someone to be paralyzed. But many times I see (in movies and TV, admittedly) some badass Jack Bauer type character kill a dude by breaking his neck. And I've heard stories about car accident victims dying instantly because of a broken neck. Why is that?
gpt
Generally the issue comes from severing of the spinal cord. If it is cut above the C3-C4 area, you will lose the ability to breath. This, combined with the loss of motor function to the rest of the bod, causes paralysis and relatively quick death. Not that the person probably won't die of asphyxiation instantly, but since they will be paralyzed you won't know the difference from a distance. Depending on the severity of the broken neck, you can also have issues with obstruction of blood supply to the brain.