“Of pain, you could wish only one thing: that it should stop. Nothing in the world was so bad as physical pain. In the face of pain there are no heroes.” – George Orwell
What is the pain gate?
The pain gate theory, also called the ‘gate control theory,’ originated in Ronald Melzack and Patrick Wall’s paper that was published in the Journal of Science in 1965 titled “Pain Mechanisms: A New Theory [1].”
The theory essentially proposed that part of the spinal cord could act as a ‘gate’ that could be opened or closed, in which it could stop or diminish incoming pain signals coming from the body before they reached the brain.
This gate could open or close to pain signals depending on different factors including;
competing signals from the body (ascending inhibition),
active commands from the brain (descending inhibition),
or both.
The specific details of how the gate operates have been debated, and in some cases debunked, but the general framework holds to this day.
How do we close the gate?
Putting aside the exact mechanisms, most of us experience this pain gate phenomenon in our own lives. Think about a time when you smashed your thumb or pricked a finger. Without hesitation, you might have squeezed, massaged, or shook your hand. What these actions do is give the brain a competing stimulus, or in other words, a different message to interpret other than the pain that is emanating from the hand.
“The pathway that goes upward carrying sensory information from the body via the spinal cord towards the brain is defined as the ascending pathway [2].” This will be the focus of this particular article.
Different strokes.
In theory, any sensation that is not perceived as pain, can turn down pain. Being aware of the nervous system's different sensory receptors and the sensations they provide us allows us to take actionable steps to close the gate on pain.
Sensory receptors can be classified in different ways [3].
1. By their structure (free nerve endings or encapsulated).
2. By their response to stimuli (what activates them).
3. Or where they are located (in our skin, muscles, internal organs, etc…).
We will focus on receptors located in the skin, and based on their response to stimuli. These are mechanoreceptors, thermoreceptors, and nociceptors.
A. Mechanoreceptors are activated/stimulated by changes in pressure or movement. There are four primary tactile mechanoreceptors in human skin:
Merkel’s disks – light touch.
Ruffini endings – skin stretch.
Meissner’s corpuscles – low-frequency vibrations, fine touch.
Pacinian corpuscle – high-frequency vibration, deep pressure [4].
You can see that almost any type of movement, whether active (stretching, exercise) or passive (manual massage, mechanical massage, mobilization, kinesiotape, TENS units) can stimulate one or more of your body’s mechanoreceptors. Stimulating these mechanoreceptors can help close the gate on pain.
B. Thermoreceptors are activated/stimulated by changes in temperature.
Ice packs and heating pads are obvious solutions. Topical analgesics such as menthol-based and capsaicin-based products work by activating thermoreceptors as well, cold and heat receptors respectively.
C. Nociceptors are activated/stimulated by tissue damage.
It may seem strange to use pain to inhibit pain, but it has its utility. Most people are familiar with “a good hurt.” From the perspective of ascending inhibition, the larger and faster A-delta nerve fibers that are stimulated by sharp pain can out-compete the smaller and slower C-nerve fibers stimulated by dull and chronic pain. This temporary sharp pain in place of a constant dull ache is partly why you can experience a “good hurt.” This is an example of counterstimulation, or more precisely counterirritation. “When two painful stimuli act on us at the same time, we perceive one of them as less painful. This phenomenon is part of the body's own pain control system [5].” Scrape therapy, cupping, capsaicin creams, menthol-based topical creams, and dry needling are just a few examples of this technique.
Is it just a distraction?
It depends on your definition of distraction. If you use the American Psychology Associations' definition then yes; “A stimulus or task that draws attention away from the task of primary interest [6].” The primary interest, in this case, is the perception of pain.
With that being said, almost all of the techniques listed above work in more ways than just distraction. Ice decreases inflammatory molecules at the site of injury and slows down nerve conduction velocity [9]. Exercise stimulates the body’s natural pain-relieving serotonergic and opioid mechanisms [8], and so on and so forth. The long-term pain-relieving mechanisms of these different modalities are not completely understood. Nonetheless, these different techniques can, at least in the short term, decrease pain by closing the pain gate.
Summary, Key Points:
The body has a ‘gate’ that can open or close to control pain.
Ascending inhibition is one component of this gate.
There are inexpensive, simple, and effective ways to close the gate on pain.
Additional Resources
History of pain.
Theories of pain.
Pain modulation and mechanisms.
Glossary
Ascending: to go up.
Inhibition: the act of preventing or slowing the activity or occurrence of something.
Descending: to go down.
Stimulus: something that causes something else to happen, develop, or become more active.
Sensory: of or relating to your physical senses
Receptors: a nerve ending that senses changes in light, temperature, pressure, etc., and causes the body to react in a particular way
Stimuli: plural of stimulus.
Tactile: relating to the sense of touch
Works Cited
1. Melzack, Ronald, and Patrick D. Wall. Pain Mechanisms: A New Theory. Nov. 1965, file:///C:/Users/Levi/Desktop/pain%20gate/pain%20gate%20ORIGINAL.pdf.
2 Yam, Mun, et al. “General Pathways of Pain Sensation and the Major Neurotransmitters Involved in Pain Regulation.” International Journal of Molecular Sciences, vol. 19, no. 8, 24 July 2018, p. 2164, 10.3390/ijms19082164. Accessed 28 Mar. 2022.
3. “12.2A: Classification of Receptors by Stimulus.” Medicine LibreTexts, 20 July 2018, med.libretexts.org/Bookshelves/Anatomy_and_Physiology/Book%3A_Anatomy_and_Physiology_(Boundless)/12%3A_Peripheral_Nervous_System/12.2%3A_Sensory_Receptors/12.2A%3A__Classification_of_Receptors_by_Stimulus.
4. “36.2A: Somatosensory Receptors.” Biology LibreTexts, 16 July 2018, bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Book%3A_General_Biology_(Boundless)/36%3A_Sensory_Systems/36.2%3A_Somatosensation/36.2A%3A_Somatosensory_Receptors.
5. “How One Pain Suppresses the Other.” ScienceDaily, www.sciencedaily.com/releases/2020/12/201221121736.htm.
6. “APA Dictionary of Psychology.” Dictionary.apa.org, dictionary.apa.org/distraction
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