What is a coma, thinking of it in a brain cells and brain signals way?

Non-reactive brain: Coma is described by the lack of patient response to stimulation. Centers in the brain stem cause us to be awake and to respond to things around us (ras). When this is not functioning properly, a level of coma can be described. The brain may be shut down by trauma, drugs, lack of oxygen, stroke, swelling, etc. The chance of recovery and the degree of recovery may be very difficult to predict.