Modern concepts of pain

All pain is real.

No-one really wants pain. This is understandable. Though pain is unpleasant, it is important for our survival. Normally, pain experiences are excellent response to what the brain judges to be a threatening situation. This is our normal damage early warning system...

Nociceptive system


This system has very specialized sensors. Some respond to mechanical force (intense pressure or squeezing), temperature changes (hot or cold), and chemical changes (allergens or chemical released by cells). These sensors, along with the sensors in the eyes (light), ears (sound and gravity) and nose (smell), are the first line of protection against potential harm.

warning system

Alarm system: Black Jack,

Smoke detector

Smoke detector: via Wikimedia Commons

IP camera

IP Camera: Intellinet Network Solutions, Wikimedia Commons

Fire alarm pull station

Fire alarm pull station: KMJ, Wikimedia Commons


The information provided by this sensor carried back to the brain by special neurons is just a surge of electric impulse. The emission of barrages of signals that does not mean pain will occur.

Digital filter

Data filter: phipatbig,

The signal can also be nullified at the spinal cord if

  1. the amount of other signals (proprioceptive) coming from the same part is normal or increased which indicates normal functioning of the part,

  2. the brain makes the judgement that alarm sounded is not beneficial for survival.

By getting rid of the "noise," the filter system provides the brain with a clear picture of what is really happening in the tissues.

Nerve impulse on graph

Nerve impulse: Chris 73, Diberri, tiZom, Wikimedia Commons

Writing script

Scriptwriting: Wikimedia Commons

At the judgement, the brain constructs a sensible story based on the information presented and in reference to its database of acquired and inherited experiences. The condemned dangers set off alarm bells, and the innocents cause no pain.

Emotions, like fear, anger and sad, affect the intensity of the story like megaphone amplifying sound. Nevertheless, a believable script can be written even without any input of damage signals, but just with thoughts.

Phone icons: 1 large, 5 small

Phone icons: alexwhite,

All emergency response systems are always on alert, and react according to the scenario.

The immediate response team members are:

  • sympathetic system - increase heart rate, increase vigilance, sweat;
  • motor system - run away, fight, protect damaged area;
  • endocrine system - mobilise energy reserve, reduce digestive and reproductive activity;
  • pain system - motivate to escape and seek help, attract attention.

The recovery operation team members are:

  • immune system - fight invaders, sensitise neurons, produce fever, make sleep to promote healing;
  • parasympathetic system - nourish cells, heal tissue.


If the story has nothing exciting, life goes on as usual. If there is a horrible scenario, siren is sounded and pain sets in. The sensation like “aching,” “tearing,” “stretching,” “burning” are created relevant to the context of the story. The amount of pain one experiences does not necessarily relate to the amount of tissue damage.

This is how we dramatize the story.

Warning Sirens Speakers sounding an alarm or warning.

Sirens: Grimgram,


Types of pain

  1. Nociceptive pain is an early-warning protective system, essential to detect damaging or noxious stimuli. It is triggered only by intense stimulation.

  2. Inflammatory pain is also protective. By heightening sensory sensitivity it assists in the healing of the injured body part by discouraging physical contact and movement as in burns, gout, rheumatoid arthritis, etc.

  3. Pathological pain is not protective. It results from abnormal functioning of the nervous system. It is not a symptom of some disorder but rather a disease state of the nervous system:
    • from nerve damage—neuropathic pain,
    • from altered function—functional pain, is evoked in fibromyalgia, irritable bowel syndrome, tension headache, temporomandibular joint disease, interstitial cystitis, etc. These may be some of the conditions leading patients to seek chiropractic care.

If pain were a fire alarm, nociceptive pain would be triggered only by intense heat, inflammatory pain would be activated by warmth, and pathological pain would be a false alarm caused by malfunction of the system itself.



Pain hypersensitivity can either be adaptive or maladaptive. After an injury it helps by warning us from moving or touching the injured tissue until repair is complete. However, if it persists long after an injury has healed or occurs in the absence of any injury, it provides us with no benefits, and is a manifestation of pathological change in the nervous system.


The two mechanisms that increase the excitability and sensitivity of neurons are:

  1. Peripheral sensitization—happens at the site of tissue damage and inflammation. e.g. when a normally warm stimulus such as a shower feels burning hot in the sunburned areas.

  2. Central sensitization—happens within the central nervous system, so that normal inputs begin to produce abnormal responses. e.g. in migraine attacks where brushing hair is often painful, and in nerve damaging conditions where blowing on the skin produces excruciating burning pain.

    Central sensitization occurs in chronic pain syndromes, like fibromyalgia, osteoarthritis, musculoskeletal disorders with generalized pain hypersensitivity, headache, temporomandibular joint disorders, dental pain, neuropathic pain, postsurgical pain, post-whiplash injury, vulvodynia, multiple chemical sensitivity, and visceral pain hypersensitivity disorders like irritable bowel syndrome, overactive bladder, and in anxiety, panic attack and depression.

This pain production model elucidates the role of CNS in abnormal pain sensation and chronic pain syndrome. It also indicates how the nociceptive pathways in addition to causing pain, can influence the whole body through its effect on autonomic, endocrine, immune and motor systems. Thus, when this pathway is not functioning properly, it will cause health problems in other systems of the body.

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