The Science of Zombies

My parents are both doctors, so I figure if I were to ever end up as a citizen in the zombie apocalypse, they would probably be part of some movement to try to figure out what exactly is going on with these dead-but-not-dead bodies running around.  I've seen civilian doctors and nurses in some of the zombie fiction we've read and watched.  In "Choice of Zombies" I managed to come across a poor dead doctor who had figured out the science behind the zombies but had died a very untimely death.  

Maybe it's because of my doctor parents, but I've been wondering about the science behind zombies since we first watched The Walking Dead.  I mean, it isn't scientifically possible for a person to walk around without a beating heart.  Without a heart, blood wouldn't pump through their bodies, wouldn't get to the brain, muscles wouldn't contract, and they wouldn't be able to move.  And I don't just mean that they might limp around and wave their arms as we've seen so many times - they physically would not be able to move.  The zombies in Warm Bodies didn't bleed, but in The Walking Dead every gunshot or sword to the head is complete with splattered blood.  I was curious if there was any general consensus to the inner workings of zombies, so I did a little research. 

My general findings were very inconclusive, but here is some of what I found:

Brain: the only part of the zombie body that is crucial to survival.  A shot to the brain will kill a zombie and also keep someone from coming back as a zombie if they haven't turned yet.  A blog post on "Science not Fiction" about zombies says that it seems that the zombie virus must "re-animate the existing neural pathways and motor functions in some fashion." A little vague for my taste.

Heart: not functioning, not crucial to life.  Again...doesn't make much sense to me.

Blood:  One website says that zombie blood is "thick and black, hence the nickname, 'zombie oil'" consistent with R's blood in Warm Bodies.  The virus that causes someone to become a zombie enters into the bloodstream and that is how it kills.  But I'm still not convinced that a zombie would be able to function without a heart to pump real blood to the brain.  Any theories?

Sense Organs: According to a section of http://www.fvza.org/zscience2.html called "The Biology of Zombies," zombies are colorblind and nearsighted, deaf, but have a very good sense of smell.  This is not consistent with what we've seen of zombies in movies and TV, where our main characters are constantly sneaking around and trying to avoid firing their guns.   

My conclusion is that no one has really given much thought to the biology behind the zombie body, but that it doesn't matter to those of us who continue to devour zombie literature (see what I did there?).  We accept zombies for what they are - the walking dead.  They don't have to make sense to exist.  They just do.