Trying to get some thoughts how a sleeping brain might sense a numb limb.

 

Most of the muscles are paralyzed but maybe the attempt to move still registers somehow. Hopefully people more knowledgeable can offer their insight.

Maybe a signal could be picked up at the level of the spine (before it ever reaches the brain)? Alternatively, perhaps it could be interpolated based on blood flow? Not sure...

Well from what I know in my limited experience in biology and knowledge, I can deduce a few answers to your question. When a limb goes numb, much of what you are feeling is the depravation of oxygen to your muscles, usually by cutting off blood circulation. The cells send electrical impulses to the nervous system to alert you of the lack of oxygen, which the impulse is registered as the feeling of numbness. The electrical impulses, if great in energy, can be enough to make you move or wake up if you're in a light enough sleep.

Edited December 13, 201312 yr by Stetson

That sounds like it makes sense. Thanks

Edited December 13, 201312 yr by Endy0816

It depends on the sleep stage of brain function. In the earlier stages (1st or 2nd), the brain could more readily detect limb numbness; however, amid the later stages (3rd or 4th) of sleep sensory information from the limbs does not reach the brain with same intensity as it does when the brain is aroused and wakeful. Amid dreaming (REM), the body's musculature enters a state of atonia, which is opposite the state of muscle readiness we experience amid wakefulness and prior stages of sleep. This is the state of sleep paralysis that many of us experience after sudden arousal from REM sleep. Amid insufficient REM sleep, arousal is possible but difficult to maintain without continual stimulation. Although many researchers believe this paralytic state evolved to prevent body movement and subsequent injury to the sleeper amid dreaming, this state actually evolved in brain function before those parts of the brain that produce dreaming. This suggest that atonia evolved for some purpose other than maintaining immobility of the body while dreaming. The neural evidence from the primitive brain structuree that produce atonia suggests it evolved to serve the metabolic needs of the body amid prolonged periods of rest.