How Acute and Chronic Pain Work

Let us analyze what pain is, from a neurological point of view.

There are two basic types of pain: acute and chronic. The former occurs as an alert, informing the brain of a damage or potential damage if a certain stimulus persists. The latter, on the other hand, is not an alert and stays for a long time, even after the traumatic event has healed.

Broadly speaking, pain develops in four steps:

·          stimulus

·          nociceptor reception

·          transmission

·          and brain reception

A painful stimulus causes nerve endings to fire a signal to the central nervous system. The signal arrives to the thalamus and from there travels to the cortex, the outermost layer of the brain. Only when the brain receives the signal in the cortex you start feeling pain. The whole process is called nociception (from noceo, a Latin word for harm or hurt).

Three kinds of stimuli cause pain:

·          mechanical (as cuts, pressure or punctures)

·          thermal (heat)

·          or chemical (as from internal inflammatory mediators)

Let us pick up one stimulus and follow the nociception chain all the way up to the brain. For example, suppose you were holding a hammer and suddenly dropped it on your left toes.

You feel acute pain almost immediately, because pressure nociceptors in your toes sense the mechanical stimulus and send a signal through neurons. Neurons are very long cells. A single neuron can connect your toe with the spinal cord.

The second link in the chain (neurons in your spine) amplifies the signal and transmits it to the thalamus. A third link connects the thalamus with the cortex. Almost all sensory information (except olfactory) reaches the cortex via the thalamus.

Looking closer, you discover the hammer caused a tiny cut in the skin of a toe. Therefore, besides a pressure stimulus, the nociceptors in the toe fired a wound signal. Histamines and prostaglandins from the immune system invade the damaged area and you perceive inflammation.

Without inflammation, the cut tissue would never heal. However, inflammation releases some enzymes —chemicals that stimulate nerve endings— and you feel more pain. Hours later, you note the difference between pain caused by the hit and pain caused by the cut.

For pain relief, you take some aspirin. Aspirin, like ibuprofen, works locally by hindering the effect of the enzymes, reduces inflammation, and, thus, reduces pain.

However, you don’t see the stimulus associated with chronic pain. Why? Because when you perceive a chronic pain the stimulus may have disappeared several months or years ago.  

There are several approaches for chronic pain treatment, depending on which of the three links in the pain chain will be attacked: locally, at the site of the damaged tissues; at the spinal cord or at the brain level.

Often, the damaged tissues that cause chronic pain show no local signs of inflammation. Acetaminophen (Tylenol), unlike aspirin, doesn’t have anti-inflammatory properties. It inhibits the production of prostaglandins, lipid compounds that exist in almost all body cells and that cause pain because they sensitize spinal neurons.

Chiropractic (from chiro; hand, in Greek) works at the second link in the chain, treating mechanical disorders in the spine and joints.

  Hypnosis and behavioral therapy work at the third link level. Acupuncture, massage therapy and other alternative practices carried out by any Toronto, Montreal, orOntario chiropractormay also provide chronic pain relief at all three levels.

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Rachel Clarson

www.TotalWellnessSolution.ca