Oh, the distribution works if there are multiple available states at a given energy level. And there are. You can even calculate it for a single particle in a box. We actually did in class...

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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.

um, no, the brain does control the heart, not sure who told you that, but they lied to you.

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> > > > > Nerves cannot be naturally regrown by the body,

Not entirely true, but in the CNS the regeneration capacity is extremely limited. Peripheral neurons can regenerate to a reasonable degree, typically guided along the existing path of supporting Schwann cells.

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.

I think all of the other answers here are sort of missing the point -- you don't need bring in entropy or statistical mechanics to answer this question.

When you've been taught that objects move to lower energy states, what is meant is they move to lower potential energy states. A ball rolls from the top of a hill (high gravitational potential energy) to the bottom of a hill (low gravitational potential energy). An electron moves from far away from the positively charged nucleus, towards the nucleus, going from high electric potential energy to low electric potential energy.

This is just how forces work. A force points in the negative direction of the gradient of potential associated with it. The gravitational force points from high to low, the force of pressure in a fluid points from high pressure to low pressure -- the direction of a force is determined by the gradient of it's potential (alternatively, you can go the other way -- if you know the force vector, you can get back to the potential by integrating it).

If you're comfortable with some calculus, you can do the math for many common potentials very easily. The gravitational potential energy on Earth is U = mgy, where y is the height, so the y-component of the gravitational force is just the negative the derivative: Fg = -dU/dy = -mg. The electrostatic potential energy is U = k q1 q2 / r, if you differentiate with respect to r, you get Fe = -dU/dr = k q1 q2 / r^2. A potential energy is defined such that the corresponding force points in the direction of decreasing potential energy.

Energy is still conserved in these calculations, because the potential energy is just becoming kinetic energy -- there's no energy being lost.

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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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So if someone is brain dead, it means their body could still function without knowing it? Say if, by absurd, that body can be hydrated and fed, can the rest of the body still be preserved?

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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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If you need an efficient, relatively painless method then boltgun beats guillotine, less set up and prep and more guarantee of breaking the brain beyond functioning.

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