Among these chemicals released is one with little known purpose in the human body, DMT (dimethyl tryptamine), the chemical responsible for dreaming, and the most powerful psychedelic hallucinogen known to man (and therefore a schedule I neurotransmitter?) even though your heart isn't beating, the neurotransmitter receptors will still be active at some level, since most proteins can still function without oxygen.
As with any drug induced trip, your perception of the final release of DMT will be based entirely on your state of mind at the time of death. If you are happy with your life, if you feel like you left the world a little better off in your brief stay here, and if you don't feel any strong regrets for your actions than it will be a pleasant experience. Conversely if you did a lot of harm, hurt others, put yourself before everyone else, and committed offences as grievous as rape and murder, that guilt will be expressed in your final "trip". If you live like this, than you will have a more terrifying experience than you could ever imagine, and coupled with the fact that DMT effects time perception, this final trip will feel like an eternity, for better or worse.
As the body and brain decompose, the proteins that make up the receptors will degrade to the point where any form of conscious, or existence will decompose along with it. But I can't stand the Idea of my consciousness disappearing for ever, so I believe that the consciousness will be imprinted on the universe in some way, this "soul" will go to a magical land of bliss, or get reincarnated, or become a noodle in the flying spaghetti monster, or whatever you believe.
so basically all the afterlife is is a psychedelic drug trip
for more information on the effects of and ethanogenic uses of DMT