What happens when we die?

Submitted by darsenalmex11 t3_11yllc0 in askscience

Not looking at the existential question but what are the biological processes our bodies go through when it decides "Alright, I'm done." What parts are the ones that start deciding to turn off and how do other parts like the brain or cells start communicating the process to the body?

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fastspinecho t1_jd8ckeq wrote

First of all, there are two clinical definitions of death. The traditional definition is irreversible loss of blood circulation. The heart doesn't "decide" to do this, but due to some injury it can no longer pump blood. This means it can no longer deliver oxygen to the rest of the body, which means most of your organs can no longer produce sufficient energy to maintain homeostasis. Among other things, cells need to constantly use energy to pump water out of themselves. Without energy, they usually swell up and rupture. Again, this is not a "decision" or signal sent to the body, any more than a balloon decides to pop when punctured by a needle.

The second definition of death is "brain death". This means that brain cells are no longer receiving blood, and are all dying for the reasons given above. Other organs may still be receiving blood, but legally the person is still dead.

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slouchingtoepiphany t1_jd8fo7h wrote

You're asking a good question. When a cell dies, it's because it loses the ability to make ATP, the product of oxidative metabolism and glycolysis and is sometimes called the "universal currency" for cellular reactions. The lack of ATP results in many things going wrong, including the cell's ability to maintain the integrity of its membranes, but many other reactions that are deleterious to the cell also take place. The cells that are most vulnerable to this are those that are the most metabolically active, which include the brain and heart. When these fail, many of the body's systems also fail and death may be declared when an individual has lost circulatory, respiratory, or CNS (brain) function.

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3intheoven t1_jd94kf3 wrote

Death isn't a biological process of the body deciding "I'm done", it's the end of all processes within the body. The chemical reactions and everything else keeping you alive slowly come to a stop, and your consciousness goes along with it. Here's a great video that might give you some insight: https://www.youtube.com/watch?v=ibpdNqrtar0

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Alcoraiden t1_jd9gheq wrote

It's not much of a communication, it's more of a lack of that. Depending on what part fails, you'll have a different order of shutdown, but essentially death happens when your body can't get enough oxygen to keep its processes going. Either your brain stops functioning and thus the rest of your body doesn't get the automatic signals to breathe and move blood, or your heart is damaged and now your brain doesn't get oxygen and you pas out and die, or...you get the idea. Maybe you lost so much blood that it just can't ferry enough oxygen to your vitals, and they shut down.

Your microbiome (bacteria, fungi, etc in and on you) will begin to eat you. If you die in an open area, larger scavengers probably will come pick at you too. Your muscles will first lock up (rigor mortis) and then loosen over time. Your body will grow cold (algor mortis), and then your skin will discolor as blood pools in whatever the lowest parts of your body are for the position you're in (livor mortis). Your skin will desiccate and retract, giving the appearance that your nails and hair have grown. As your muscles relax, you'll release whatever was in your bladder and bowels at the time. Amusingly, if you have a penis, you'll probably get an erection for a while.

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fastspinecho t1_jd9ioe5 wrote

Replying to flyfruit__ (#2,308,112)

Yes, the rest of the body could still function.

That said, it probably wouldn't function for that long. The brain has "autonomic" functions that help maintain proper blood pressure, etc. After it's gone, the body will eventually become hemodynamically unstable and cardiac failure is pretty much inevitable. I suppose some future medical advances might one day prevent that. But really, why bother?

In practice, brain death is legal death. Hospitals will not provide life support to a dead person, unless they are an organ donor. So once brain death is diagnosed, one way or another that person will soon be in the morgue.

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Rebeccalon787 t1_jd9jymz wrote

Replying to flyfruit__ (#2,308,112)

Yes, witnessed it first hand. Was there to pull the life support because I was told they were dead. Took me talking to doctors for an explanation as to why they were vocalizing, of course just sounds, eyes open and moving, body twitching. Was hard in that moment to believe this person wasn't "alive". It took less than 20 mins after the life support was removed, so I know I made the right decision. Still tough to wrap your mind around it in the moment.

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flyfruit__ t1_jd9lblg wrote

Replying to fastspinecho (#2,308,247)

Yeah, that is why I asked the question. It looks amazing to me that, if a person is brain dead, even if the brain is autonomic, the body's organs can still be preserved for as long as it can: I assume probably 3 days to one week max.

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SweetStrawberry4U t1_jdawsll wrote

Life is a multi-constituted process, and so is Death. Several aspects that actually make Life livable, Die similarly.

https://youtu.be/LVlFJPOGyWE

In short, it takes anywhere between 2 hours to 14 days, for Life to end, and therefore Death to 'occur'. Constitutes, involuntary and voluntary systems, Immunity, buoyancy of the spine, temperature regulation etc.

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rdrast t1_jdb236e wrote

Replying to flyfruit__ (#2,308,112)

Yes, the autonomic system, keeping heart and lungs working can still keep running, even if the cerebral cortex is completely gone.

The autonomic system is deep in the brain, and is the ladt to go, normally.

ETA: at the point there is no higher brain function (stimulus to light, sound, pain) "You" are essentially dead, but the body can continue to function, since a basic thing is to keep going.

The autonomic systems really will keep going, provided oxygen and food.

Sometimes for years.

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IdontOpenEnvelopes t1_jdcfn74 wrote

Q: "Daddy, what happens when you die at the hospital?"

A: " They clean the bed and admit another one".

The body has many cascades of failure, the net result is cardiac arrest. Now cardiac arrest is just medical death and it can occasionally be reversed through resuscitative efforts depending on a myriad of factors. Legal death is when you are beyond salvage.

Your cells need sugar and oxygen to make energy to operate the Sodium/Potassium pumps to keep the sodium out, when the pumps stop sodium floods the cell and causes lysosomes to explode due to osmotic gradients- this releases digestive enzymes into the interior of the cell causing it get eaten from the inside. Thats cell death.

Now your brain is the main user of energy, when blood flow slows to a critical level, the neurology starts to get disregulated causing your autonomic nervous system to spazz out driving your organs through predictable stages of disregulation and failure.

The lungs start to fail from the lack of blood flow causing more blood to bypass them without picking up oxygen- this aggravates the above. Also causes permanent damage to the lungs.The build up of CO2 causes your blood to become more acidic - which accelerates organ failure and cardiac and neurological disregultation leading to failure.

Your kidneys are very sensitive to blood pressure being in the right zone, when the BP gets too low your kidneys fail- causing a rapid build up of metabolic wastes and an electrolyte imablances- this effects all the organs - most critically the heart muscle and muscles of reapiration - both very sensitive to Sodium/Potassium levels.

The slowed blood flow in the tissues causes local acid/base balance disregulation which cause clotting in the capillary beds - you end up with disseminated intravascular clotting- which accelerates all of the above.

The above doesn't include any of the hormonal disregulation that accompanies the cascade of failure.

Eventually, you endup with seizure, coma, death.

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HalcyonDreams36 t1_jdcjdlb wrote

Replying to flyfruit__ (#2,308,112)

We call that "life support"... A vegetative state, where the body functions are fine but the brain activity is gone.

Typically, that's a temporary state, while they evaluate the possibility of a person waking up (are they brain dead, or potentially just comatose?), and if the former, give families time to make decisions, come to terms, say goodbye.

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noirxgrace t1_jdcyo3l wrote

Sight is the last sense to go
Brain is the organ that survives the longest amongst all other organs
In short, you turn pale; all the blood in your body settles down on the area closest to ground creating bruises; then body goes cold no heat signature; then rigor mortis sets in i.e. your joints become rigid and position of body cannot be changed; then all organs in your body liquify and bloat your body from inside with fluids and gases; then you start decomposing with scavengers of the the society like maggots, insects and animals feeding on you and breaking you down until you turn in bones

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Kalanthropos t1_jdo4jwo wrote

Replying to zekromNLR (#2,359,473)

That's the thing, it raises a lot of philosophical questions. How do we define "death" if we can maintain the unity and function of the organism by supplanting its systems? What is the appropriate use of this technology?

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zekromNLR t1_jdop6ko wrote

Replying to Kalanthropos (#2,359,577)

True. My personal answer to this is that I consider a "person" to be the processes that occur in the brain from which consciousness arises via some mechanism that is not yet well-understood, with the body more or less just being a vessel for those processes to occur in and for the consciousness to interact with the world.

And so my personal opinion is that the only real use for keeping a braindead body alive would be to keep its organs viable until transplantation, but I do understand that that is probably an opinion that is quite far to the materialist side of things.

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