Why is the Pain Unbearable?

Pain is experienced every day in a multitude of ways: stubbing your toe, spilling coffee on your hand, or bumping into something.  But what is pain?A simple definition of pain is “physical suffering or discomfort caused by illness or injury.”

While pain can seem pesky and useless sometimes, it is arguably the most essential defense mechanisms of living organisms, especially human beings. What we call pain is the connection between the body receiving physical harm, and the brain cognitively recognizing this fact through the complex nervous system.  This may seem like a strictly biological reaction, but chemistry plays a crucial role in biology.  This blog will explore the ways of reducing pain from a chemistry standpoint.

Before we begin discussing some of these ideas and concepts more in-depth, some background knowledge is necessary.  Different types of pain come from varying causes, and therefore must have different forms of relief. One approach to types of pain is to split the concept into acute and chronic. Acute pain is often sudden and sporadic, and will dissipate quickly. This can be a result of concentrated damage to tissue such as muscle, organs, or bones. On the other hand, chronic pain is usually longer lasting and more difficult to relieve.

The Wiederrich Chiropractic Clinic offers a great visual representation of these different types of pain.

Within these two main types of pain, there are three general categories of pain.  Damage to your tissues, such as a burn, causes nociceptive pain after special nerve endings called nociceptors are irritated.  Neuropathic pain is caused by damage to the nervous system. Often this pain is also picked up nociceptors through either illness or injury.  The third form ispsychogenic pain, or pain that is affected by psychological factors.

Obviously these definitions cannot help to relieve pain, but pain can be relieved in several different ways. Many of these remedies will be discussed in future blog entries. It is most logical to begin with the most basic, primitive form of pain relief of acute pain injuries – temperature! When a soccer player twists her ankle, a dancer sprains his calf, or a member of a baseball team is hit hard in the thigh by a wild pitch  fibers of the affected muscle tendon, and/or ligament are immediately disrupted. Capillaries, tiny blood vessels that usually carry blood and oxygen to these tissues, break, releasing various amounts of blood and serum into adjacent tissues. Swelling and bruising are immediate visual results, followed by physical pain. Soft tissue injuries, as just described, coincide with nearly all physical injuries.

After a soft tissue injury, most victims follow the cheap and efficient medical recommendation for pain relief: ice the injured area for the first 24-72 hours, followed by soothing heat. This is the oldest trick in the book, and it works. Initially, ice or another cool material causes the damaged capillaries to constrict blood vessels, stopping further leakage. Coolants will also prevent swelling and pressure on areas surrounding the injury. Several days after the

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injury, a change of temperature is required if the pain persists. Blood clots have already stopped all internal bleeding or “leakage” at this point, and the addition of heat allows blood and serum leakage to be reabsorbed from the tissue into the body.

 

How does heat allow muscles to stretch and loosen? Think about the chemistry! First off, this is a reaction we know must happen; the free energy will be negative. It is also obvious that the process of heating a tight muscle is an endothermic reaction; heat is going into the muscle – our system for this reaction. For the same reason, the temperature by nature is very high when heat relief is used. This stands to say that the entropy of the system MUST be positive, both logically and on paper. Muscles and leaked fluids will expand and stretch out as they now have more possibilities of arrangements. Coolants work the same way, but with opposite results. They produce exothermic reactions at low temperatures and are clearly spontaneous. The entropy of a coolant system is accordingly positive. This relates to the constriction of blood vessels and muscle tissue, minimizing possibilities of arrangements of the fluids immediately leaked from tissue following a soft tissue injury, as well as loosen the muscles to prevent further strain.

Only even more interesting topics are yet to come.  Can’t wait for the next post? Is the pain of time passing killing you? Even more information can be taken from this informative video from Khan Academy. The first half of George Zaidan’s TED-Ed animation also goes into more detail about how we feel pain. More information about different types of pain can be found on the St. Jude’s Medical Website. In future posts we also plan to discuss real-life implementations of these understandings, and explore other ways pain relief can be described through the science of chemistry. Equipment and treatments such as Game Ready and NASA’s Grow Lights are only beginnings of possibilities.

 

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