h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

That's pretty much it, really.

one is a natural part of your life cycle

the other is usually induced by external factors

you reaction to painfull stimuli will be different in each state

Do you dream if you're unconscious?

I drempth when I spent a few months in a coma hooked up to lifesupport in a hospital.. and even by my standards they were pretty weird dreams...
Or, at least I seem to remember dreaming whilst I was in the coma, the mind isn't always the most reliable source of information on such details

I think that if you were to be unconscious you wouldn't wake up when the alarm went off in the morning?

There would be different brain activity/inactivity according to whether it's unconsciousness/coma/sleep, as well as variety within each state.

Also, I'm fairly sure that when I was in a coma, for the most part it was a medical drug-induced coma (though it may have been a 'natural' coma to start with).

"People who are under anesthesia or in a coma are often said to be asleep. However, people in these conditions cannot be awakened and do not produce the complex, active brain wave patterns seen in normal sleep. Instead, their brain waves are very slow and weak, sometimes all but undetectable."

From Brain Basics: Understanding Sleep, National Institute of Neurological Disorders and Stroke, National Institutes of Health

http://www.ninds.nih.gov/disorders/brain_basics/understanding_sleep.htm

"....Instead, their brain waves are very slow and weak, sometimes all but undetectable."... But, that's me when I'm awake half the time

Only half?

Yeh... only half... as the other half of the time I'm either entirely in a coma or fast asleep

2legs- when you were in a medically induced coma, was this the result of some sort of court order or petitioetition?

Well the short answer is that it's easy to wake up from sleep, you can wake someone up by moving or shouting them. If someone is in a coma you can't do that. If you are not sure if someone is in a coma or not you have to try and wake them up!

During sleep the body is quite but there is lots going in the brain with lots of well recognised brain wave activities, and they really need to happen, as a lack of sleep can make you very very ill. During a coma the parts of the brain that control awareness are not working properly so that however much you are shaken you *can't* be awake.

So what is it that causes someone to emerge from unconsciousness?

It brings to mind James Herriot, in one of his vitnery books saying that he thought that drugging serious cases gave them a chance to heal themselves quietly, without the conscious stress and fretting...

?

If you have lost consciousness due to injury, and have had sufficient time to heal, you should regain consciousness. If you have lost consciousness due to anesthesia, and have had sufficient time to metabolize the anesthetic, you should regain consciousness.

Barring complications.

So unconsciousness is a sort of shut down while the body heals itself, which is either a brain response or chemically induced?

More of less how Ikinda understood it; when I was in a coma (december to err March I think 1993), it was following a major injury and they stopped my regaining consciouness by use of drugs, in order that things could kinda get on doing a bit of healing on their own without at that time further surgical work... It was, I seem to vaguely recall also something to do with p helping in particular prevent inflammation, and all the various chemicals released during the infmatory process, which would have done more harm than good to the bits of my body which hadn't quite been wrecked already... I do recall or at least think*I recall some very weird 'dreams' from that kind of period though...

I've heard of extra weird dreams, from a friend, after major cancer surgery, who was kept under for several days (he had extra months of life, maybe a year).

Yes, unconsciousness can be either due to illness, illness of the brain or elsewhere, or due the use of drugs, which is called a general anaesthetic.

You wake up when either the illness gets better or the drugs wear off, usually the anaesthetic drugs wear off quite quickly, within less than an hour, so on intensive care they are given by a continuous infusion. The commonest reason for keeping someone under anaesthetic, or continuous sedation is because they can't breath for themselves, and to have a ventilator doing the breathing for them you have to sedate them. There are other reasons too, but I leave that to the clever ITU doctors.