Your Brain Still Works After Death

Should we reconsider how we define death? Are we really dead the moment our heart stop functioning? 

Apparently after one is declared dead the brain is continuing to work 10 minutes afterwards, and the memory center is the last part of the body to give in to death(after). In this period everyone has different neurons firing off in this part of the brain. Meaning everyone has a unique experience in this periode. Do we watch our life in review in those minutes? Or what really happens?
Not only that but our genes continue to work until 2 days after death and they are highly active.
Is it ethical to pronounce people dead when some parts of their body are still working?
And what does this mean for those whose organs are donated immediately after death?

When are we dead? What do you think?