Name: Pleasant Lane
What makes your arm fall a sleep?
Your arm falls asleep when, for example, you drape it over the back of a
chair or sleep on it for a long time. This is caused by cutting off the blood supply
to the nerves, which then stop working. When the nerves don't work, you can't feel
sensations in the arm or move it very well, if at all. When the blood supply is
restored, the nerve cells carrying pain information recover first, so you get pain
and tingling sensations before you recover fine movement. Very occasionally, paralysis
can be permanent if the blood supply is cut off for a long time. This is sometimes
called "drunkard's paralysis" because people who are drunk sometimes pass out in such
positions for a long time.
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Update: June 2012