The origin of pain

Although it seems natural to think that the sensations of pain have their origins in the same place as the tactile stimuli, such is however not the case.

painful stimuli

The perception of painful stimuli , i.e. nociception , depends on specialized receptors and pathways . In addition, the response to pain involves many components: pain discrimination (location, intensity, type); affective and emotional . All of this is intertwined in a complex network specific to painful sensations.

pain receptors

Distributed throughout the body, there are many pain-sensing receptors . They are called nociceptors . They all have their definite characteristics. Some will react to burns, others to acidity, others to pressure, etc. The painful information is then transmitted to the brain through a network of dedicated fibers . These are very small caliber fibers which conduct information very slowly (<2m/s). These pain fibers do not activate on too light stimuli . You have to reach a certain threshold to activate them and convey the painful information. Research has also revealed larger caliber fibers capable of conveying both pain sensation and tactile sensation . Due to a larger caliber, these fibers conduct information much faster (30m/s). It is for this reason that when you hit your foot, for example, you feel a very sharp initial pain. Then, gradually a second, more diffuse pain sets in. It is the activation of these different fibres, at high speed then at slow speed, which causes this sensation of having two painful sensations which set in.

Brain areas

When the information arrives at the level of the brain, it will be dispatched in a multitude of cerebral areas .

These areas will interpret different information such as:

• the location of the pain ,
• its intensity,
• its character (burning, sharp, throbbing, etc.).

• unpleasant feeling ,
• the fear,
• anxiety ,

as well as all the accompanying vegetative reactions , such as the adrenaline rush to allow escape in case of danger. Some patients who have had brain surgery, where some of these areas have been removed, describe losing the unpleasant sensation associated with pain. As the emotional system is extremely complicated and different from one individual to another, this explains why we do not react in the same way to pain.