Pain acts as the body’s warning system, often alerting us to illness or injury. Pretty much all of us have experienced some degree of pain throughout our lives. However, the different ways in which we experience pain can be very complex. This phenomenon is due to the many factors that shape our perception, including combinations of physical stimuli with our thoughts, emotions and past experiences.
Many theories of pain exist in an attempt to capture a particular understanding of pain, which helps to enable various practitioners to formulate treatments and recovery programmes in order to counter these symptoms.
Popular Theories of Pain: Gate Control Theory
They proposed that the gate in the spinal cord modulates the transmission of sensory information from the primary afferent neurons to transmission cells in the spinal cord. Or in simpler terms, pain signals need to encounter certain neurological gates at the spinal cord level and these gates determine whether the pain signals should reach the brain or not.
Nerves from all over the body run to the spinal cord, which is the first main meeting point for the nervous system. In the spinal cord, you might imagine a series of gates into which messages about pain and many other signals arrive from all over the body. The activity in the large and small fibres controls this gating mechanism. Large-fibre activity ‘closes’ the gate, whereas small-fibre activity ‘opens’ the gate.
If this neurological gate is open, the pain signals are perceived by the brain as more intense. Conversely, if the gate remains closed, or limited, the pain is perceived as less intense.
These are several factors that cause the neurological gate to be more open; such that the pain feels more severe. When one experiences a high level of stress or tension, he or she becomes more susceptible to the opening of pain gates. Stiff joints and lack of movement in the body are common factors contributing to open neurological pain gates.
On the contrary, feelings of happiness and optimism have found to be positively associated with closing the gates to pain. Being in a relaxed state and immersing oneself in other interests are also found to be effective. Maintaining healthy fitness levels and engaging certain types of counter-stimulation have also proved to be effective in blocking pain signals.
As illustrated earlier, greater activity from large-diameter nerve fibres activates the inhibitory cells in the dorsal horn, thereby blocking pain signals. Following this theory that nerve fibres show a higher response to touch, pressure and vibration, treatments that capitalize on these inhibitory responses will help to curb pain signals.
Popular Theories of Pain: Endogenous Opioid Theory of Pain
The endogenous opioid system comprises a wide array of receptors and ligands that are present throughout the central and peripheral nervous system, the gastrointestinal tract, and the immune system. This system explains the multitude of physiological functions it is responsible for, including analgesia, mood regulation, and modulation of the stress response.
Endogenous opioids are a class of molecules that are produced in the brain and circulate widely throughout all organ systems. Endorphins are one of the endogenous opioids in humans, which are naturally released in response to pain. The secretion of analgesic (pain-relieving) opioids is achieved by stimulating nerve endings with high-intensity electromagnetic fields using frequencies in the range between 2-10 Hz, as well as via mechanical stimulation via joint manipulation and other methods.
Popular Theories of Pain: Peripheral Pattern Theory of Pain
The Peripheral Pattern Theory of Pain describes the pain as coded information sent through the peripheral nervous system to the brain interpretation center, where it is decoded and interpreted.
This theory considers that the peripheral sensory receptors, in response to touch, warmth, and other stimuli, give rise to non-painful or painful experiences as a difference in the patterns of the signals sent through the nervous system.
Thus, according to this view, people feel pain when certain patterns of neural activity occur. Because strong and mild stimuli of the same sense modality produce different patterns of neural activity, being hit hard feels painful as compared to being caressed, which does not. It suggests that all cutaneous (relating to the skin) qualities are produced by spatial and temporal patterns of nerve impulses rather than by separate, modality-specific transmission routes.
Transcutaneous electrical nerve stimulation (TENS) consists of a generic application of low-frequency, pulsed electrical currents transmitted by electrodes through the skin surface to stimulate the peripheral nerves to produce various physiological effects. It is a non-invasive and inexpensive mode of therapy widely applied in clinical practice.
It is considered one of the most common therapeutic resources used for the relief of chronic and acute pain. On top of its analgesic effects, some studies have observed its effects on the peripheral vascular system, showing increases in blood flow, and therefore, possibly facilitating tissue repair.
Treatments for Chronic Pain
As discussed above, chiropractors may help patients with pain by way of several common theories describing why people experience pain. Besides manual therapies, some chiropractors may use some form of therapeutic technologies in their treatment of chronic pains.
For pain management, a number of therapeutic devices may produce changes in the electrical impulses in the tissues or how those signals are read by the brain. For example, electrotherapy may involve stimulating tissues with a range of electrical frequency ranges to reduce pain, improve circulation, repair tissues, and strengthen muscles to improve physical function
Another popular device for pain management in recent years has been radial shockwave therapy. This device works by way of providing high-frequency percussion to the skin, and mechanical “shockwaves” penetrate deeper into the tissues. This may stimulate the release of local opioids and disrupt painful nerve sensations from these tissues to the brain. It is also a useful device for the breakdown of scar tissue and the growth of new blood vessels into a damaged area, which helps with recovery and mobility.
However, these therapies are not typically used as standalone treatments, but often along with a range of other passive treatments and active exercises. For example, people undergoing physical therapy might find that electrotherapy helps to alleviate pain enough for them to participate more effectively in prescribed exercises.
Pain is a Complex Phenomenon
Most modern treatments are formulated based upon theories and understandings of how we feel pain. The theories described above are just some of the many theoretical frameworks that have been proposed to define the physiological basis of pain. It is important to note that despite convincing studies, none yet wholly accounts for all aspects of pain perception. Other theories date back to the 1800s, with the Intensive Theory, Specificity Theory, Pattern Theory, to Gate Control Theory of Pain and more.
The Gate Control Theory is the most proclaimed of pain theories and resulted in some of the most fruitful research in understanding the perception of pain. However, although each of these theories adequately describes a series of observations about pain perception, none completely capture the complexity of the pain system.
Thus, when doctors or therapists are treating patients with pain it is important to take into account many factors about that person’s life in addition to physical irritants or sources of pain. Psychosocial factors, neurological stress, genetic components and many more may all be involved, and thus why it is important for people suffering from chronic pain to find the right combination of treatments and lifestyle advice which can most effectively solve their concerns.
About the Author
Dr. Michael Bryant completed his degree in cell & molecular biology and pre-medicine at the University of Michigan, before working for a short while in medical research and genetics. He went on to attain his doctorate in chiropractic and was fortunate to gain exposure to neurological-based protocols for patients with a wide range of conditions during that time.
He is currently the director of Elite Spine Centres in Singapore and enjoys incorporating principles of neuroplasticity and mind-body training into his patients’ treatment programs.
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