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Wednesday, October 21, 2009

Why is it that I can (for example) pinch my arm and feel a tingling in my chest?

I assume it's got something to do with nerve endings getting crossed. But is there a more informed answer?
Answer:
There is a rough map for where the nerves in your skin correspond to areas in the spinal cord called a "dermatomal map"- you can find these all over the place, but the fact is that everyone is different, so the nerves of your skin may be very similar to mine, but the map may be completely different from someone else's. In general if you stimulate the nerves in that particular area, it will connect to the corresponding part of your spinal cord, but some nerve fibers do not.All of your sensory neural pathways originate in various areas of your skin, and synapse (connect to other nerve cells) first in your spinal cord. Certain types of fibers travel up and down a few segments before synapsing, and the case may be that the synapse for some of the nerve fibers from your arm may be near the synapse for fibers in your chest. So depending on the size of the stimulus, neurotransmitters (the chemicals that communicate signals) may "spill over" and cause you to feel sensations in other areas. This is natural, and occurs in everyone, though it is sometimes difficult to detect.
i feel a tingle on my lower back sometimes if i scratch my upper arm. I really don't know how or why, but I'm glad I'm not the only one!
Not getting crossed. The nerves that supply your arm begin in your spine, and branches go through your chest. The phenomenon you describe is called referred pain, and a common example can be seen in heart attack patients who feel pain down their arm.

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