We all experience pain. Sometimes even our own organism causes pain by causing inflammation. Although we all feel pain, we are not well aware of the sensory neurons involved. In this article we will talk about nociceptors, the pain receptors.
All humans (and all other living beings with a central nervous system) would like nothing more than to feel no pain. Believe it or not, however, experiencing pain is very important in life.
If we were immune to burns, injuries, or the physical symptoms of an illness, we would most likely live a very short life. In addition, people with congenital insensitivity to pain are known to lead tragic and short lives.
Pain is like a warning and helps us respond to dangerous or harmful stimuli. For example, we could say that nociceptors guarantee our survival because they allow us to have a better quality of life and to have a much better relationship with ourselves and our environment.
As mentioned before, pain is necessary and we cannot live without pain. What exactly is the biological cause through which we experience it? We can say that the pain receptors of the brain are the only culprit.
They do, however, need the help of a few allies who detect painful stimuli and a complex network that relays the information from that experience, such as the thalamus and sensory nerves.
In addition, nociceptors are responsible for detecting these unpleasant sensations. They are nerve endings (the ends of axons) that are located throughout the body.
They are located in our external tissues (the skin) as well as in every part of our internal physiology (muscles, intestines, bladder, ovaries, and so on). They assess the damage of the body when we experience pain. In other words, they are responsible for transferring that information to the central nervous system.
It is important to note that humans and animals are not the only living things that have these sensory receptors. Some of the simplest organisms have nociceptive functions. We all need these structures to survive.
Types of nociceptors
These are the nociceptors located in our body:
- Chemoreceptors respond to certain chemicals that our tissues release during an infection, inflammation or disease. These are substances such as bradykinin and histamine, which reach the blood when we are injured, when a cut becomes infected or when we receive a blow.
- Thermoreceptors are the pain receptors that are activated when we come into contact with a surface or element with a very high temperature. Often we experience this painful feeling without knowing what happened or what we touched.
- Mechanoreceptors are activated by a mechanical pressure that can injure the individual or deform the body tissue. This is the most common form of pain and the fastest we notice because this information travels through the Aδ fibers.
- Silent nociceptors take a long time to activate. They are located in inflamed tissues, right next to an injury.
- Polymodal nociceptors are a challenge for scientists because they respond to every kind of stimulus we mentioned above.
Why can pain become chronic?
What do we know so far about nociceptors?
- First, that they are located at the end of the axons.
- Second, that they respond to dangerous thermal, mechanical or chemical stimuli.
Now we also know that certain types of pain are more tolerable than others and that some conditions make the pain chronic. Certain experts determine that the pain is proportional to the severity of the injury or dysfunction.
For example, if you cut your finger, the pain will not last more than two or three days as long as you clean and treat the wound properly. However, burns are different. Severe injuries like these damage more tissue, making the healing process much more complicated.
On the other hand, it is also important to distinguish nociceptive pain from neuropathic pain. The first is produced by mechanical, thermal or chemical stimuli. However, neuropathic pain is associated with damage to the nervous system.
There may be a small neurological change that causes those axons or pain receptors to respond more intensely and sustainably to each stimulus. The latter is associated with debilitating conditions such as fibromyalgia.
Science faces the challenge of developing more sophisticated and personalized medicines, chemical agents that respond to the concrete pain receptors that cause pain, so that it no longer affects the quality of life of people suffering from serious injuries or conditions.