Originally posted by Astyanax
reply to post by TheFearless
Yes, there is an explanation, and it's fascinating.
The human family tree is full of arboreal ancestors - creatures that really lived in trees. If they fell asleep in the wrong place or at the wrong time, they'd fall out of their trees and die. So one of these ancestral species developed a reflex to keep that from happening - a sudden sense of falling that came over them as they were drowsing and snapped them awake so that they could, if necessary, move to a safer position before falling asleep and out of the tree. It worked, and those creatures survived to have offspring, evolve and - pass on the reflex.
That jerk you feel is your apelike ancestors' anti-fall reflex in action.
And before some clever-clogs points out that this is a just-so story: I know it is. What of it?
[edit on 24-11-2008 by Astyanax]
Originally posted by must be a way
This is a common sensation and often accompanied with an uncontrollable 'jerk' as you try to recover.
I had to research this a good few years ago after nearly breaking my ex wife's nose whilst experiencing this..............(wish I had now )
Its known as a hypnic jerk and apparently 70% of people have them.
it is caused by a confusion between the brain and muscles as you fall asleep and is of no need for concern!!!
In normal sleep the brain releases control of the muscles to allow for near still restfull sleep however sometimes and mostly when extremely tired or out of your normal sleep pattern the conscious mind is able to sense the release of muscle control which gives the sensation of falling, then the conscious kicks the brain in to force your body to compensate....usually resulting in a very sudden tho short violent jerk.