Nociseptors: All About Pain Receptors

We all experience pain. Sometimes even our own organism causes pain by triggering inflammation. Now, even though we all feel pain, we are not well informed about the sensory neurons involved in it. In this article we talk about nociceptors, the pain receptors.

All humans (and all other living beings with a central nervous system) will love nothing more than not feeling pain. But believe it or not, experiencing pain is the key to life. If we were immune to burns, injuries or physical indicators of a disease, we would most likely have lived very short lives. Furthermore, it is known that people with congenital analgesia (insensitivity to pain) live tragic and short lives.

Pain is like a warning that helps us respond to dangerous or harmful stimuli. Thus, we can say that nociceptors guarantee our survival since they allow us to have a better quality of life and relate much better to ourselves and our environment.

Nociceptors

As mentioned earlier, pain is necessary and we cannot live without it. But what makes us experience it, when it comes to biology? We can say that the brain’s pain receptors are the only culprits. However, they need the help of some allies who discover painful stimuli and a complex network that transmits the information to that experience, such as the thalamus and the efferent nerve fibers.

In addition , nociceptors are responsible for detecting these unpleasant experiences. They are nerve endings (the end of the axons ) that are located throughout the body. They are found both in our external tissues (skin) and in all areas of our internal physiology (muscles, intestines, bladder, ovaries, etc.). They assess the body’s damage while we experience pain. In other words, they are responsible for transmitting this information to the central nervous system.

It is important to note that humans and animals are not the only living beings that have these sensory receptors. Some of the simplest organisms have nociseptic functions. We need all these structures to survive.

Types of nociceptors

Here are the types of nociceptors we have in our body:

• Chemoreceptors respond to certain chemicals that our tissues release in the face of an infection, inflammation or disease. These are substances such as bradykinin and histamine that reach the blood when we get an injury, when a cut becomes infected, or when we suffer a stroke.
• Thermoreceptors are the pain receptors that are activated when we come in contact with a surface or an element with a very high temperature. We often experience this painful feeling without even knowing what happened or what we touched.

• Mechanoreceptors are activated by any mechanical pressure that can damage the individual or deform body tissue. This is the most common type of pain and the fastest we notice since this information passes through Aδ fibers.
• Quiet nociceptors take a long time to activate. They are located in inflamed tissue, right next to an injury.
• Polymodal nociceptors are a challenge for researchers because they respond to all types of stimuli we mentioned above.

Why does the pain become chronic?

What do we know so far about nociceptors? One, that they are at the end of the axons, and two, that they respond to dangerous thermal, mechanical or chemical stimuli. We now also know that certain types of pain are more bearable than others, and that certain conditions make pain chronic.

Some experts determine that pain is proportional to the severity of the injury or dysfunction. If you cut your finger, your pain will not last for more than 2 or 3 days as long as you clean and treat the wound properly. However, burns are different. Serious injuries like this damage more tissues, which complicates the healing process much more.

On the other hand, it is also important to distinguish between nociseptive pain and neuropathic pain. The first is produced by mechanical, thermal or chemical stimuli. However, neuropathic pain involves damage to the nervous system. There may be a slight neurological change that would cause those axons or pain receptors to respond more intensely and persistently to any stimulus. The latter is related to debilitating conditions such as fibromyalgia.

Science faces the challenge of developing more refined and personal substances, chemical agents that act on the specific pain receptors that trigger pain, so that it no longer affects the quality of life of those who suffer from serious injuries or disorders.