Question regarding hand in warm water prank?

Several people have posted on the famous hand in warm water trick whereby submerging a sleeping person's hand in warm water while asleep induces urination. Many people have claimed they have heard of this prank, but I want to know how many people have truly witnessed this in person.

I am also curious to know if anyone has any plausible hypothesis as to how it works. I understand the micturition reflex (urintation reflex) is a spinal reflex with regulation from higher brain centers, but how exactly the warm water would trigger the urination is of interest to me. Do you think the warm water evokes the spinal reflex or causes enough activation such that it overcomes the tonic inhibition from higher brain centers. I'm very curious to see what ideas people propose.

4 Answers

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  • 1 decade ago
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    This is a theory.

    Heating the hand causes the blood in small capillaries to heat up, or more likely stimulates thermoreceptors in the skin. A rise in body temperature will reduce the sympathetic outflow to the smooth muscle in the blood vessel walls allowing dilation and cooling of the skin.

    The sympathetic nervous system is also responsible for allowing bladder filling. If sympathetic stimulation is decreased the parasympathetic will dominate, allowing the internal urethral sphincter to relax and the bladder to contract. Although these two things should not be linked, could there be some crossing over in effect?

  • 4 years ago

    Hand In Water Prank

  • 1 decade ago

    I've heard it's simply the warm water causing muscles in the body to relax, including the prostate. It, no question, doesn't work 100% of the time.

  • 1 decade ago

    never seen it personally.

    Have heard that the warm water causes the person to relax.

    You know, you get that "warm feeling" all over.

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