Halakhah for Oholot 1:9

The Rambam in his commentary on Mishnah Oholot 1:7 defines the "halachic brain" as the control center for bodily movements. The hypothalamus is not part of the halachic brain, but rather a secretory tissue, no different from other glands of the body which secrete hormones. It does not control the body's motion. Upon death many parts of the body remain viable for various lengths of time without affecting the decision to declare the patient dead.