Though in a normal human brain all blood flow ceases at death, in zombies this may not be the case. Prevailing hypotheses suggest that the modern zombie is controlled by its brain, and for a brain to work it needs blood.
A brain without blood flow would very quickly dry out, crack, and become little more than a lump of brittle nothing. University of California, Berkeley Neuroscience Professor, Marian Diamond, echoed this sentiment:
“The brain is dead if there is no electrical activity. Without blood irrigation, all channels would flatten, and there would be no brain function, and no sitting up or walking around.”
If blood does move through zombie bodies without the aid of a beating heart, we must then consider what might be driving the system.
One prominent hypothesis argues that increased electrical charges in the brain spur blood flow through a process of magnetic attraction and repulsion. Another argues that zombie blood acts as an independent agent, propelling itself.
As is often the case in the study of zombies, a single possible answer leads to many more questions.