why is some pain sharp and sudden, while other pain is dull/achy and constant?
In: Biology
Your skin and other tissue contains receptors which are responsive to different kinds of pain (mechanical, heat, cold, etc). These receptors activate signals in different nerve fibres which carry the signal to your brain. The fibres have different properties (diameter and how they are insulated, like electrical wire) which affect how fast the signal travels to the brain. A nerve with a large diameter and a lot of insulation will carry a signal very quickly. A thin, uninsulated fibre carries information more slowly.
When you touch a hot surface, for example, the sharp initial pain is the signal of fast nerve fibres. These fibres also communicate with reflex loops which move your hand away without needing your brain to instruct it to. This is then followed by dull, throbbing pain which is caused by impulses travelling along slow fibres. Residual, aching pain is also transmitted through these slow fibres.
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