Pain: physical suffering or discomfort caused by illness or injury

The feeling of pain is your body's way of warning you of danger. When you touch something hot or bend your arm the wrong way, the pain receptors send the warning signal to your spinal cord and up to your brain. This reaction triggers an immediate reaction (pulling your hand away, etc.), but many people react differently because of varying pain tolerance.

"Pain tolerance" is the level of pain a person can stand compared to their physical and mental reactions to it.

According to recent studies in North Carolina, your level of pain sensitivity has to do with the amount of gray matter in someone's brain. The gray matter holds most of the brain's neuronal cells. It controls peoples' muscles, senses, emotions, and decisions. Previous research, however, shows that the person's previous encounters with pain and their current mental state affect how they react.

One out of a million people have been diagnosed with congenital analgesia. This rare genetic disorder prevents people from feeling pain at all. This may sound amazing- not being stopped by any limitations- but this disorder is less of a blessing and more a curse. Many injuries go without notice and become infected, which can lead to more serious and permanent injuries. Insensitivity to pain can develop if your nervous system doesn't develop entirely, or the pain-sensing part of the system doesn't work. People with congenital analgesia have completely developed nervous systems but the neurons that pass the signal to the brain don't work.

On the opposite side of the spectrum is hyperplasia. This disorder means the subject has increased sensitivity to pain. This can either occur because of injured nerves or a temporary illness that increases pain to help fight infection. Hyperalgesia can also be caused by some long-term treatments of certain chronic pains. As bad as this sounds compared to complete freedom from pain, it is often considered the better option. Although you feel more pain, you can avoid the long-term, serious injuries caused by neglect as a result of congenital analgesia.

Even for people without these disorders, how can you tell if something is seriously wrong with yourself (without a medical degree, of course)? When you fall on your wrist, how can you tell if the pain is telling you that it is twisted or broken? If you've never broken a bone before, what do you compare the pain level too? Every year, experiment by experiment, scientists grow closer to understanding the human brain. In the past few years, scientists have managed to measure people's pain levels through brain scans, but they still have quite a while to go. The complexity of the human brain and nervous systems is so far ahead of our knowledge currently, that there are those who believe that we will never fully understand how our own brain's work.