ELi5 Why is it that when you hit your knee or elbow you can get that numbing pain sensation rather than a direct stubs kind of pain?
In: Biology
There are different types of nerve fibers that produce different types of pain and travel at different speeds. Often the first sensation after an injury is very fast and sharp. This pain is carried by the A-type nerves. After a few seconds you will feel a fuller burning sensation that is carried by the C fibers.
But when you hit your “funny bone” you are hitting a nerve bundle that is exposed. The ulnar nerve runs along the elbow in a place that is easy to hit, and hitting it affects sensation in all the areas that the nerve innervates.
The tingling is from a nerve being hit. For example in the elbow it’s the ulnar nerve. if you hit a toe you’re impacting skin, muscle, fat, bone, and some nerve endings but the ends don’t have further nerves to propogate sensations to.
Think of lightning striking the ground. If it hits on a wire, the electricity flows through that wire to the end of it and will shock anyone along the way. When you hit your nerve the same thing happens.
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