The Sensitive Nervous System Chapter IV: Central Sensitivity, Response, and Homeostatic Systems

This is a summary of Chapter IV of David Butler’s “The Sensitive Nervous System.” Intro Central sensitization is a phenomenon that occurs in the dorsal horn, which can be best described via 4 different states: 1)      Normal: Inputs = outputs; innocuous sensations are perceived as such. 2)      Suppressed: Inputs that would hurt do not; think an athlete who injures himself but finishes the game. 3)      Increased sensitivity: Pain system has lower activation threshold, leading to pain spreading and pain with light touch and gentle movement. This change occurs because A beta fibers begin taking over C fiber locations in the dorsal horn. 4)      Maintained afferent barrage, CNS influences, and morphological changes: Long lasting changes in the dorsal horn from a persistent driver, such as… A fiber phenotype changes. Persistent DRG discharge. Persistent inflammation. Supraspinal influences Gene transcription change in dorsal horn neurons. Inflamed dorsal horn or DRG Maladaptive beliefs, fears, and attitudes. Dorsal horn sprouting; A Beta fibers take over C fiber space. Persistent glutamate activity. Descending Control The CNS has an endogenous pain control system which activates during injury threat, noxious cutaneous input, or expectations and learning. Such an example of this is when you go to a healthcare practitioner’s office and no longer hurt. Another example of when this system is activated is during aggressive manual therapy. Think about how good your body may feel after sustained pressure or even a needle to a trigger point. Central Sensitization Patterns Areas/descriptors Symptoms not in neat anatomical/dermatomal boundaries. Original pain

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