A friend of mine says that the brain continues to have some sort of function after the body has died. Is that true?
Well, if by “the body has died”, your friend means that the heart has stopped, then, yes, the brain can continue to live for a bit after the heart has stopped. If the heart stops for too long (usually only a few minutes), the brain begins to die, and once that happens, even if the heart is restarted the person is likely to have lasting brain damage.
If by “the body has died” your friend means that the guy is dead, in the ground, buried, then the function of the brain is the same as the rest of the body – to provide food for the bacteria and other agents of decomposition.
Well, it’s true that the brain doesn’t immediately cease functoning after somatic death (the cessation of respiration and heartbeat), but within a few minutes at most, brain death follows which, by definition, is the complete cessation of brain activity.
It was always my understanding that stopping brain activity by cutting off oxygen and brain death which cannot be reversed are separate things. Granted they aren’t separated by more than a few minutes.
Yes. As a paperweight. Otherwise, depending on how you define death, any residual brain activity is going to be measured in minutes, at best. The brain is a pretty energy-intensive organ and without oxygen, it stops functioning almost immediately.
I think the crux of the answer is that life/death is not a completely binary choice, lots of gray areas. As Miracle Max said in SDMB’s favorite movie, “mostly dead means a little alive.” Sometimes your dead relatives tell you to go back, sometimes you stay with them.
Thanks for all the answers. 
Another question: My friend also says that it is the supposedly still functioning brain that initiates the decomposition of the body.
I remember from biology classes (10+ years ago) that when the body is dead, cells release some chemicals that accelerate the process of decomposition. What is the straight dope on that?
Zev Steinhardt
The big guy has touched upon the subject of brain activity after death in his light and frothy decapitation column.
Maybe he’s getting it confused with an old episode of Tales from the Crypt.
Lots of humans seem to function relatively well after evident brain death. Our current political candidates, for instance.
Let’s keep political snipes out of General Questions.
Thank you.
DrMatrix - GQ Moderator
In mot states,determination of death has changed, to keep pace with technology. Now, Cessation of brain function is the legal definition.
This is determined by, a brainflow study. If no blood is getting to the brainstem, its dead.
If the brainstem isn’t working, nothing above it can be.
There are also a series of physical criteria that determine brainstem function.
Removing artificial ventilation for 1, 3 & 5 minutes, while continuing to deliver oxygen. arterial CO2 is checked at each milestone. If one’s CO2 is high, the brainstem (at least, live ones) tells the body to take a breath. If the CO2 raises to a predetermined level, without any attempt to take a breath, the brainstem has gone south.
The other test is called a cold caloric, or Doll’s Eyes test. Ice water is instilled into the patients ear, then the head turned carefully side to side. If there is any brainstem activity, the eyes will deviate and have nystagmus. Otherwise, the eyes look like a doll’s eyes would, straight ahead. (DON’T TRY THIS AT HOME, KIDDIES It hurts.)
These tests have to be preformed in the face of normal body temp and normal electrolyte levels. They are, again, administered 12 hours later. If no activity is stimulated the patient is pronounced dead.
Of course, if family is available, and consent to removal of life support, the tests are moot.