Eli5: Why does it feel like I’m falling while trying to sleep?

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Sometimes, when I’m laying in bed, trying to sleep, I feel like I’m falling. Obviously, I jolt in order to save myself, only to find I wasn’t falling at all and was still laying in bed safely. Why does that happen?

In: 12

It’s called a myoclonic jerk. They’re very common but not entirely understood. The best explanation I came across was that when you lay down, your blood pressure drops precipitously (too fast). Your brain senses this sudden drop and gets worried that you might have an injury or are otherwise in danger, so it releases the emergency brake on your adrenal system and dumps chemicals that raise your heart rate, bringing your pressure back up to normal.

Not a proper Eli5 (far too speculative), but I’ve also pondered this:

Your brain is in the process of isolating itself from the normal senses to reduce stimulation from the outside world – I have a suspicion that it’s not entirely unlike the strange behaviors one might see in an online game if the internet suddenly goes out, but the game hasn’t yet acknowledged this. Some components might try to carry on the last action (e.g. rubber-banding in walk cycles, aimless AI behaviors), but others might behave much more strangely e.g. objects falling through the floor.

Basically, your brain is a universe-simulator, and when the outside data driving it gets cut off, different parts of the brain might respond in ways that are difficult to rationalize – in this case, I have a suspicion that it’s something like a prompt dismissal of the feeling of weight, but too early in the sleep induction process to avoid that jerk reflex.

Also called a Hypnic Jerk.

Myself and a friend suffered these a lot when we were younger, most acutely from our mid to late teens. We used to skateboard back then, and there are theories that link these jerks with physical exhaustion.

I rarely suffer with them as an adult, but if I am really overtired through lack of sleep or exercise, I’ll likely have a jerk or two.