In Max Brooks’s book, The Zombie Survival Guide, he says that the virus that reanimates a zombie is called Solanum. It works by traveling through the bloodstream, from the initial point of entry, the bite, to the brain. The source of Solanum is still unknown. Solanum is 100 percent communicable and 100 percent fatal. There is no cure. Infection can occur only through direct fluidic contact. The most common means is a zombie bite.
Hour 1: Pain and discoloration (brown-purple) of the infected area. Immediate clotting of the wound (provided the infection came from the wound).
Hour 5: Fever (99-103 F.), chills, slight dementia, vomiting, acute pain in the joints.
Hour 8: Numbing of extremities and infected area, increased fever (103-106 F.), increased dementia, loss of muscular coordination.
Hour 11:Paralysis in the lower body, overall numbness, slowed heart rate.
Hour 16: Coma.
Hour 20: Heart Stoppage. Zero brain activity.
Hour 23: Reanimation
For more check out his books. He talks about outbrakes and what you can do to keep yourself alive when the zombies take over the world.
The next step is to analyse in more detail the aspects of their physiology. This information was either stated in the movies or can be determined based on observation.