​​Coma typically is a sign of minimal mental activity due to the failure of the brain to function properly. Their body can still exercise involuntary actions like breathing, digestion and heart beating, but cannot respond to external stimuli that require voluntary actions such as responding to pain, eating and defecating. In some cases, comatose people may need machines to help them breathe normally. Normally, a coma will last for a few weeks before slowly regaining consciousness. Any longer than that will progresses a coma to a vegetative state or even worse, brain death.