Sometimes you wake up from sleep in the middle of the night and you find yourself unable to move your arms, they seeming to be dead weights. Or you get up from where you have been sitting for some time without any movement and you feel an uncomfortable and strange tingling sensation in your legs. There would be hardly anybody who hasn’t encountered this situation, of finding their limbs ‘asleep’ after they have put pressure on them for some time. This phenomenon is technically known as Paresthesia, and is caused by the compression of specific nerves in our body. The most common situations they occur in are when one sleeps with one’s arm above the head, and sitting cross-legged for a while. It is like loss of sense and can last a brief period of time. During this time, you can’t hold anything with your hand steadily and would find it clumsy.
As said earlier, the reason for this experience is the compression of nerve pathways in the body. When you apply pressure on a certain part of your body for a prolonged period of time, the nerves and arteries in that part get squeezed. It leads to disruption in blood circulation as well as the nerve functions. The nerves carry signals of sensation to the brain and the instructions of brain to various parts of the body. When you exert pressure on a body part, you are effectively blocking this communication. Also the small arteries that carry nutrients to the nerve cells compress under pressure and cause the cells to behave erratically. These cause the failure of the nerve cells to send proper signals of bodily sensations to the brain and the brain can’t give them the right instructions either. Some cells stop communication while others would send abnormal signals. As a result, you lose feeling in the corresponding body part or feel a tingling or vibration.
When the pressure is lifted, the nerves would begin to work properly and the blood circulation would also regain its natural speed gradually. You would take a few moments until can feel your limbs again and this period is marked with strong sense of being poked with pins. This is because various nerves take different time to regain the natural flow.
The limbs’ falling asleep is not a dangerous scenario for the body, unless it is for a very long time. If the communication from brain to the nerve cells is cut off for a very long period, it may cause serious damage to the cells and result in the permanent loss of sense in that part.
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