• Question: When a person dies how long is their brain active for??

    Asked by prey50vet to Andrew on 9 Nov 2021.
    • Photo: Andrew McGovern

      Andrew McGovern answered on 9 Nov 2021:

      After we die, many cells in the body take up to 12 hours to halt. Things like skin or immune cells.

      But, the brain is the most oxygen hungry part of our body and our brain cells need oxygen to survive. We can lose consciousness in under minute without oxygen but we almost never have full recovery of brain function after 3 minutes without oxygen. This indicates that consciousness doesn’t remain for very long but the evidence we have shows that brain activity halts after ~7 minutes.

Comments

  • Photo: Henry

    Henry commented on :

    As Andrew says, we believe that brain function cannot normally be recovered after about 3-4 minutes after blood stops flowing to it. But this is a very interesting question, because it opens up the conversation about how we define when a person (or animal) is dead!

    In hospitals, we often use the time at which the heart stops beating as the ‘time of death’ on a person’s death certificate. But of course we know that we can (sometimes) restart a person’s heart with a jolt of electricity. Even more interesting is that a small number of animals (some fish and some frogs) can spend every winter completely frozen solid, and then re-animate in the spring as if nothing had happened. There are scientists exploring the ways in which these animals are able to survive completely frozen, as it may help humans create ways to preserve humans (cryogenic freezing) for things like deep space travel.