Where pain really comes from

Imagine that there is a wound that does not seem very large. A cut on your index finger, a few centimeters long. Nothing really serious. A band-aid is all that is needed to stop the bleeding.

But still, the moment the blade of the kitchen knife sliced through the skin, the irritated pain receptors (also known as nociceptors) fired pain signals to the brain via the A-delta fibers at 110 kilometers per hour. This happens because there are about 250 sensory cells per square centimeter on the finger whose job it is to transmit pain and temperature sensations to the brain.

For the vast majority of people, pain is an unpleasant experience that they try to avoid. Yet, pain is necessary for our survival. Pain signals to our brain about abnormalities in the body and imminent danger. But there is more than one kind of pain. Not only does each person perceive pain differently, but it is also different from person to person.

Broken bone pain does not come from the bone

Some types of pain are fast, brief sensations, such as those transmitted by fast A-Delta fibers. Dull pain, such as that transmitted to our central nervous system by the slow C-fibers, is usually caused by chronic inflammation and can only be roughly localized by the person experiencing it. C-fibers usually detect the stimulation of nociceptors in our organs.

While most of our organs are equipped with nociceptors, there are parts of our body that cannot feel pain. These include our brain, intervertebral discs, and bones. When a bone is broken, it is not the bone itself that hurts, but the surrounding tissue that is injured by the fracture. But while it may seem that medicine has figured out all there is to know about pain, it is still very much a work in progress for scientists.