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Monday 29th August 2016
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Why does our leg jerk just as we're going to sleep?


sleep.jpgI hurt my knee yesterday and it hurts when I am just getting to sleep and then my leg spasms. Why does that happen?
Matt, Acton


** Joint-definitive **
Name: Stuart, near the London Eye
Qualification: I watch House a lot
Answer: It’s known as a Myoclonus reaction, which is what happens when  your blood pressure drops – due to a decrease in brain activity - so much that your brain panics and thinks that your heart has stopped, so it sends a bolt of adrenaline to your heart, which is what causes that jerk reaction when you’re asleep.
(James O’Brien: I can’t give you a round of applause for it as I don’t know how medically accurate House is. It sounds good, but we need more proof on the blood pressure bit.)

** Joint-definitive **
Name: Lawrence, London
Qualification: Doctor
Answer: I hate to argue with Hugh Laurie, but I think that’s wrong.  It’s known as a hypnagogic event, due to a disorder. Normally when we fall asleep, the part of the brain that controls the muscles and movement switches off, which prevents us from acting out our dreams. But in some cases, that doesn’t happen for a while, so you get movement when you’re falling asleep.
(James O’Brien: Is it possible that both you and Stuart are right?)

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