Rigor mortis (the period that the body is very stiff starting a few hours after death and lasting a few days) is something that could be inverted. Maybe it could happen earlier, later, longer, or shorter than normal...or not at all in your story.

Also, the pupils are usually very dilated on death...maybe they aren't in your story. Maybe there is still some activity in a particular organ like the heart, brain, or lungs in your version while all of it ceases in real life.