It helps to first understand a bit about nociceptors. Nociceptors are sensory receptors that respond to stimuli that are or could be harmful. Nociceptors are located in your skin, muscles, joints, and some organs, and they send information to the brain. There are different types of nociceptors which receive different types of information such as temperature changes, chemical changes, and mechanical changes (changes in pressure or form).
Temperature changes are not inherently harmful, but extreme changes could be harmful (think heat stroke, frostbite, or a burn). Our ability to sense chemical changes are why a controlled amount of menthol or capsaicin can help with pain relief, but too much of the wrong type of chemical can cause a chemical burn. And while the typical pressure from a hug is comfortable, the pressure that creates an incision causes tissue damage. Being able to sense these changes helps keep us alive!
Key takeaway— nociceptors are cool and send useful sensory information to the brain. But what happens to that information?
As we just mentioned, the nociceptors send all sorts of useful sensory information to the brain. That information can relay something as gentle as a leaf falling on your skin or something more harmful like stepping on the legos that were left out…again! Until it gets to the brain though, it’s all just data. The brain receives the information and determines if there is a credible threat.
For more information on the brain’s process of determining threat credibility, check out Lorimer Moseley’s TedTalk from 0:32-5:16:
As shown in Moseley’s example, the brain is not perfect about determining threat credibility. In fact, it can be very, very wrong. The brain is always calibrating its response to sensory data from the nociceptors.
Based on the brain’s interpretation of sensory data, its responses can vary. Upon receipt of data, the brain can determine that there is no threat and send back a signal for no pain. It can prompt a rapid recoil response such as jerking your hand away after touching something that is unexpectedly hot. It can send a “bracing” response to increase muscle tension to stabilize an injured or aggravated area. And of course, it can issue pain signals ranging from mild to excruciating.
So that’s the process— data goes to the brain, and if the brain determines there is a credible threat (regardless of if that threat is truly harmful), the brain issues a pain response.
Now that we’ve covered how the process works, let’s look at some of the most common ways the pain process can be influenced.
The intensity of stimuli matters. Nociceptors have a threshold which must be met in order to trigger the pain signal process. This means that the absence of pain does not necessarily indicate an absence of dysfunction. Imbalances and dysfunction can build, but until a certain intensity is reached, you won’t feel pain as a symptom. Anyone used to getting maintenance massage sessions has likely experienced unexpected pain when pressure is added to an area that wasn’t hurting prior to being touched. The pressure from the massage increased the stimuli in that area enough to reveal the building dysfunction.
Our subjective evaluation of sensory signals can influence the level of pain experienced. Think of seasoned athletes who interpret a “burn” during a workout as a positive experience since it indicates a process that will result in muscle growth or increased endurance. Newer athletes may interpret the same type and amount of stimuli as potentially harmful and, as a result, experience more pain.
Emotions can also play a role in the pain experience. Negative emotions can influence the physical response to sensory stimuli, resulting in an amplified pain response with increased discomfort. Negative emotions can also have a psychological impact on pain including increased attention to an area receiving negative sensory stimuli. Why does how much attention we give an affected area matter? Because the brain is getting tons of data all the time, and there is a competition for what gets processed. By giving more attention to an area with negative sensory stimuli, those stimuli get preferential processing treatment. Once again, the discomfort experienced may be exacerbated.
Another quick note on attention— the processing competition explains why new pains “show up” as primary pain complaints are resolved. When a pain issue is resolved, the negative stimuli in that area has decreased and is no longer flooding the brain. As a result, other areas with negative stimuli are able to be processed. Voila! Pain is felt in a new area even if nothing has changed in that new area.
We’re not talking about your appreciation for the feelings of others. We’re talking about how easily your nerve receptors respond to stimuli. Nerves have the ability to increase and decrease in sensitivity. In some cases, such as when there is inflammation, nerves can become so sensitive that they respond to non-harmful stimuli. When this happens, the brain may interpret a light touch as excruciatingly painful.
Where have we landed on all of this? Yes, pain signals come from your brain as an interpretation of data gathered by sensory receptors. So technically, the pain is “in your head.” Your subjective interpretation, emotions, and attention can even influence your pain experience. These things all process in your head, too. But the fact that pain signals come from your head and can be influenced by your conscious and subconscious thoughts doesn’t make the pain you experience any less real or any less of an issue.
Chronic pain and injuries can cause us to deal with pain much, much longer than we typically think we can endure. Understanding how pain is happening and what may be influencing it can sometimes offer sanity on the journey to resolving those pain issues. This is especially true when the path to recovery does not feel particularly linear.
Understanding the meaning of pain’s presence and re-defining pain as a symptom can improve our connection with our bodies and increase our willingness to address bodily dysfunctions as they arise.
If anyone ever tells you your pain is all in your head, you can tell them they’re right. You can also tell them that they’re a jerk.