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Science Behind Pain

By: | Tags: | Comments: 0 | December 17th, 2019

Pain is a very complex and important phenomenon. Most of us have experienced it at some point, and want rid of it as soon as it starts but sometimes it can be very persistent. In this article, we will discuss the science behind pain as the current research understands it. Future articles will apply this science on how to manage and eventually decrease your pain.


What is pain and how does it work?

Pain is defined as “an unpleasant sensory and emotional experience associated with actual or potential tissue damage”. The key word here is potential. Of course, we are likely to experience pain with actual tissue damage such as a broken bone or a cut on the skin, but it can also occur if your brain believes there is a chance of damage. Pain is an alarm system and if your brain believes there could be damage, it will ring the alarm loud and clear.


To understand this concept, we must look at the scientific side of things. We have tiny sensors called nociceptors all throughout our bodies. A nociceptor’s job is to send warning signals to the spinal cord and usually the signals will get sent all the way up to the brain. It’s important to note that these signals are not “pain signals” – they are warning signals that are basically saying “this could be dangerous, let’s send all the information we have up to the brain and let the brain decide.”


Once the signal is up in the brain, the brain makes a subconscious decision of how important this information is. The brain receives this message and wonders “is the danger real?” It will use every bit of information available to it (which is A LOT) to make this decision. Your brain considers past and present experiences, your feelings, memories, fears, concerns, anxiety levels, etc, etc, etc to help answer yes or no. Remember this all happens within milliseconds without you even realising it’s going on!


If the answer is “no,” then you’ll go about your business without ever knowing what happened.


If the answer is “yes, the danger is real”, the brain will send alarm signals to the original area in question with the goal of making you stop doing whatever it is you’re doing to bring up this question in the first place. These alarm signals will most likely involve pain, but also could have qualities like stiffness, burning or aching associated with them.


For example, if you’ve unintentionally placed your hand on a hot surface, your brain will send painful signals to that hand to get you to move your hand quickly to avoid damage. If you haven’t seen the hot surface, your brain may not perceive the burning part of the signal yet. Have you ever touched something very hot and it almost feels cold at first until you realise it’s actually hot? That’s an example of how the brain’s knowledge of what is going on can affect the signals that are sent and ultimately the type of sensations that we feel.


In the same example of touching something hot, the pain may come on before there is any actual damage to the skin. The brain perceived potential damage and sent painful signals to get you to remove your hand before any actual tissue damage could occur.


This example is a simple way of showing how the pain system works brilliantly in our bodies to protect us. Our subconscious systems learn, adapt and evolve to protect us the best way they know how. Charles Darwin would argue it does all of this with the goal of protecting us so we can get through life, at least until we successfully create offspring (1).


Unfortunately, like many other parts of our bodies inside and out, things don’t always go as planned. As much as our tissues, spinal cord and brain work together to protect us, it’s not uncommon to get their wires crossed from time to time. Often, we experience pain when there is no actual or potential damage in our tissues.




What is Persistent Pain?


Persistent pain (often called chronic pain) at its most basic definition is pain that has lasted more than 3 months. It is generally referred to when we have pain that persists without any known reason.


We’ve talked about the basics on how the pain system (alarm system) is supposed to work. When it comes to persistent or chronic pain, our alarm system can become faulty. The slightest movement or the lightest touch might cause the nociceptors to send danger signals up to your brain. Your brain will recognise these signals as a big problem and send a very loud alarm to theoretically stop you from causing what it perceives will be “further damage.”


Basically, the alarm system becomes extremely sensitive. It’s like a faulty smoke alarm that goes off for something small like burnt toast. Or an ear-piercing car alarm that goes off just from someone walking too close to the car.


With persistent pain, this sensitivity occurs on a cellular level. There are changes that occur in the skin, nerves and spinal cord that cause danger signals to be sent to the brain from input that previously wouldn’t even be on the danger radar; i.e. a soft touch. Danger signals take a pathway up to the brain and these cellular changes make that pathway more like a super highway without a speed limit.


The brain can also become sensitive to other types of information. Remember, your brain uses your past and present experiences, your feelings, memories, fears, concerns, anxiety levels, etc to decide if it should send a protective (painful) signal to your tissues. For example, if you know someone who has become crippled because of back pain you may be afraid of your pain and anxious about the future. These feelings can actually contribute to a more heightened and sensitive alarm system, i.e. send more painful signals to your tissues.


Body regions around the original painful area may become more sensitive as well which can create a sensation of pain that “moves around.”


All of this can occur because your body and brain have your best interests in mind and have the intention of protecting you. (2)

We’ve all started out doing something helpful that ended up going horribly wrong, and we ended up needing to clean up a big mess afterwards; figuratively or literally. The best news here is, this persistent pain mess CAN be cleaned up – these adaptations in sensitivity can be reversed. Our cells are always changing and growing and they can gradually, over time, be put on a path of returning to a “normal” level of sensitivity. Our brains can learn they don’t have to act on feelings of fear and anxiety. You aren’t destined for a lifetime of the smoke alarm going off when you’ve burned toast.


You have taken the first step today by reading this article. Understanding the science behind pain can already give input to the brain that the danger signals may not be as dangerous as originally thought.


In future articles, we will discuss specific “diagnoses”, learn about tissues that are often blamed for persistent pain (i.e. discs, facet joints, sciatic nerves), and learn about strategies to help continue the reversal of sensitivity which can help decrease your pain.


The information in this article is gathered from:

  1. Explain Pain, Second Edition, Noigroup Publications, Adelaide, Australia, 2013. Butler, D., Moseley, L.
  2. Recovery Strategies, Lehman, G.