What is the physiological difference between sleep, unconsciousness and anaesthesia?
In: Biology
I suppose you could start with sleep being a state from which you are rousable, whereas unconsciousness and anaesthesia are not.
The physiological differences are probably better explained by a neurologist, but the EEG (brainwave) features of sleep are different to those in anaesthesia. Sleep has different wave findings depending on your stage – REM has quite an active EEG, deep sleep less active etc.
Anaesthesia (general) is a different beast. It’s a drug-induced reversible state of reduced consciousness, pain relief and (much of the time) muscle relaxation. It is not a rousable condition – the entire point of it is to stop you from feeling/being conscious of the goings ons in the operating theatre. Depth of anaesthesia can be measured by EEG, and the findings are characteristically less active. The anaesthetic drugs we use essentially switch off the neurones in the brain; this doesn’t happen in sleep. If you give enough of an anaesthetic drug you can even induce isoelectric EEG – i.e. no activity at all.
Unconsciousness – physiology depends on the cause. If it’s a brain bleed, you’ll have different brain activity to say, a seizure lasting 40 mins. They’re both unconscious states if you’re not rousable. General anaesthesia could also be described as controlled unconsciousness.
Source: anaesthetic/ICU doctor
Edit: there have been quite a few complaints that this isn’t very ELI5 – I agree, sorry. I was responding more to the question and when it used a term like “physiologic” I assumed a bit of knowledge to be honest. I don’t think any of the analogies I’ve seen are accurate enough to describe the differences so I haven’t reappropriated them. Feel free to ask questions if you don’t understand though, I’m trying to get round to answering most of them.
Simple version –
Sleep: someone can wake you up if they poke you hard enough. Your brain is listening and ready for it. Imagine needing it so you don’t get eaten by a bear clomping around in the middle of the night.
Unconsciousness: no matter how hard I poke you, you’re not waking up (but you’re still alive). Your brain is on vacation and forgot to leave an out-of-office email.
Anaesthesia: same as unconsciousness, but in a controlled fashion.
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