Body Link

You can prevent your own death by decapitation or dismemberment. Your body parts become linked so that even if they are separated from the rest of your body, you remain in control of them. A severed arm can still write and even wield weapons. A severed leg can still hop around. A severed head can still think, talk, and even eat, although the rest of the body will become inert. If the severed body part is held against the stump during the spell’s duration, the two parts will instantly fuse together.

This does not prevent you from taking damage from the dismemberment or from other damage, nor does it prevent you from being killed from methods other than dismemberment.