Pain and Gate Control Theory
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Questions and Answers

What is responsible for the paradoxical analgesic effect of capsaicin?

  • Central sensitization
  • TRPV sensitizers
  • Exogenous TRPV1 activators
  • Long exposure to capsaicin (correct)
  • Which type of fibers can begin to produce pain at low thresholds in the context of central sensitization?

  • D fibers
  • B fibers
  • E fibers
  • C fibers (correct)
  • What contributes to tactile allodynia in the spinal cord?

  • Long exposure to capsaicin
  • Inhibition of GABA and glycine (correct)
  • Activation of neuropeptide receptors
  • Endocannabinoid anandamide
  • Which neurochemical receptors play a major role in central sensitization?

    <p>mGluR and NMDA receptors</p> Signup and view all the answers

    What effect does damage-induced inflammation have on TRPV sensitization?

    <p>Increases sensitivity</p> Signup and view all the answers

    What is a key consequence of CNS plasticity after nerve injury?

    <p>Loss of inhibition from the dorsal horn</p> Signup and view all the answers

    What is the role of prostaglandins in pain perception?

    <p>Enhance the painprovoking effect of bradykinin</p> Signup and view all the answers

    In the context of gate control theory, how does non-painful input affect painful input?

    <p>It closes the nerve gates to painful input</p> Signup and view all the answers

    Which neurotransmitter is involved in amplifying the pain signal?

    <p>Substance P</p> Signup and view all the answers

    What is the main characteristic of neuropathic pain?

    <p>It results from nervous system injuries</p> Signup and view all the answers

    How does peripheral sensitization contribute to pain hypersensitivity?

    <p>Lowers the threshold and increases excitability of nerve cells</p> Signup and view all the answers

    What is the impact of TRPV1 expression changes in diabetic neuropathy?

    <p>Leads to thermal hyper- and hypoalgesia</p> Signup and view all the answers

    Study Notes

    TRPV1 Activators

    • Exogenous: temperature > 43°C (109°F), acidic conditions, capsaicin
    • Endogenous: low pH (acidic conditions), anandamide, N-oleyl-dopamine, N-arachidonoyl-dopamine

    TRPV Sensitisers and Desensitisers

    • Sensitisers: damage, inflammation (Prostaglandins, bradykinin activation of PLC) → increased sensitivity
    • Desensitisers: long exposure to capsaicin → paradoxical analgesic effect

    Ectopic Activity and Clinical Targets

    • Spontaneous pain after injury: paresthesia, dysthesia, pain
    • Clinical target: voltage-gated Na channels

    Central Sensitization

    • Amplifies pain and reduces threshold
    • Mechanistic explanation: low threshold A or C fibers can produce pain, spread of sensitivity beyond areas of tissue injury or damaged nerve territory
    • Players: synaptic changes, NMDA/AMPA/mGluR glutamate, substance P, NK1 receptors, Aβ fibers, neuropeptide expression, physical changes in spinal circuitry
    • Loss of inhibition: GABA and glycine in the spinal cord

    Pain Definition and Classification

    • Definition: unpleasant sensory and emotional experience associated with actual or potential tissue damage
    • Classification: nociceptive (transient, chronic), neuropathic pain, benign, cancer pain

    Nociceptive Pain

    • Capacity to detect potentially damaging stimuli
    • Classification: somatic (deep, superficial), visceral (sensitive, stretch, ischaemia, inflammation)

    Neuropathic Pain

    • Major health problem: injured nervous system, persistent neural changes, increased sensitivity, decreased threshold
    • Susceptible persons: genetic polymorphisms
    • Heterogeneous/pathologic neural plasticity: differing etiologies, genetic/environmental factors
    • Pathophysiology: sensory nerve damage, direct insult to primary neurons/peripheral neuropathy, cell death, decreased transduction, conduction, transmission

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    Related Documents

    Pain Pathways PDF

    Description

    Learn about the concept of pain, including prostaglandins, substance P, and chemicals that inhibit pain transmission. Explore the Gate Control Theory to understand how non-painful stimuli can alleviate pain.

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