‘If two contrary actions be started in the same subject, a change must necessarily take place, either in both, or in one of the two, and continue until they cease to be contrary.’ –Spinoza
Scientists have traced chronic pain to a defect in one enzyme in a single region of the brain. Could this be a decisive turn in the battle against pain? (…)
As neuroscientists learn more about the biological basis of pain, the situation is finally beginning to change. Most remarkably, unfolding research shows that chronic pain can cause concrete, physiological changes in the brain. After several months of chronic pain, a person’s brain begins to shrink. The longer people suffer, the more gray matter they lose. (…)
Normally, pain is triggered by a set of danger-sensing neurons, called nociceptors, that extend into the organs, muscles, and skin. Different types of nociceptors respond to different stimuli, including heat, cold, pressure, inflammation, and exposure to chemicals like cigarette smoke and teargas. Nociceptors can notify us of danger with fine-tuned precision. Heat nociceptors, for example, send out an alarm only when they’re heated to between 45 and 50 degrees Celsius (about 115 to 125 degrees Fahrenheit), the temperature at which some proteins start to coagulate and cause damage to cells and tissues.
For all that precision, we don’t automatically feel the signals as pain; often the information from nociceptors is parsed by the nervous system along the way. For instance, nociceptors starting in the skin extend through the body to swellings along the spinal cord. They relay their signals to other neurons in those swellings, called dorsal horns, which then deliver signals up to the brain stem. But dorsal horns also contain neurons coming down from the brain that can boost or squelch the signals. As a result, pain in one part of the body can block pain signals from another. If you stick your foot in cold water, touching a hot surface with your hand will hurt less.
