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neurons and pain (Pain (Nociceptors (capsaicin and Transient receptor…

- - - - physical stimu, type, intensity, location
    - - unpleasant emotions
    - - anticipation, viewing in others mirror neurons
  - - - injury, compression, inflamation stimu peripheral nerves
        
        not obvious tissue damage
        
        event on peripheral nerve/CNS
        
        e.g. Stroke
        
        lesion interrupts transmission
        
        triggers pain anywhere in body
    - - from synaptic plasticity in CNS
      - altered nociceptive function
        
        Phantom limb?
    - - stimu activates noci-sensors
      - most familiar
  - - - threat of integrity
      - Skin layers
        
        Superficial
        
        no nociceptors
        
        epidermis removed w/out bleeding
        
        Dermis
        
        contains nociceptors
        
        Meissner and Merkel discs detect pressure
        
        Ruffini bodies detect vibration
    - - but in meninges of brain
    - - polymodal sensors
        
        chemical agents e.g. capsaicin
        
        heat/cold
        
        mechanical
      - Not always free nerve endings
        
        nociceptive Schwann cell
        
        subepidermal border
        
        glio- neural complex
        
        schwann cells sensitive to painful pressure-> excite sensory neurons-> nociceptive info trasmit
    - - Capsaicin causes conformational change
        
        Ca+ flows in down conc^n gradient
        
        depolarisation ->AP
      - Also responds to mechanical pressure+ heat/cold
      - TRP-V1= primary pain receptor
        
        TRP-V1 knock out mice
        
        hot plate
        
        lick paws less
        
        Caterina et al 2000
- - - - unmyelinated inside
  - - - 10 laminas (zones)
        
        Zones 1,4 and 5 involved nociception
      - in spinal cord grey matter
  - - - In dorsal horn grey matter
        
        ascending fibres to brain
        
        Lamina 5
        
        Stimu dorsal horn tract system
        
        Stimulator implanted in belly
        
        direct/ epidural electrical stimu of spinal cord
      - polymodal - intensity must be stronk
      - wide receptive field
        
        compared to nociceptive specific n
        
        subject to plasticity
        
        role in treating chronic pain
      - Excited by Aβ+ C
        
        Aβ
        
        Greater excitation WDR and greater inhibition
        
        C only excites both WDR and SG
        
        amplifies pain
      - Substantia gelatinosa neurons (SG)
        
        GABAinergic inhibitory neurons
    - - stimu dorsal column inhibits pain
        
        e.g. stroking babies
        
        TENS
        
        Transcutaneous Electrical Nerve Stimu
        
        place wires above pain area
        
        high freq electrical stimu
        
        1 more item...
- - - - one of most important regions mediating pain
  - - - predicts chronic pain
        
        In Fibromyalgia
        
        Osteoarthritis
    - - ↓ activation dorsolateral prefrontal cortex
  - - - 2 identical creams
        
        'neutral'
        
        'Lidocaine'
        
        decreased activation
- - - - Golgi I
        
        long axons
      - Golgi II
        
        shorter axons
      - Golgi - Italian neuroanatomist
        
        devoed staining technique (Golgi method)
  - - - muscles and glands
        
        withdrawal
    - - process gathered info
        
        everything else done by interneurons e.g. thinking
        
        emotional
    - - 5 senses surroundings + interoception+ propioception
        
        BP, HR, Temp
        
        orientation
      - signal danger through pain
      - Vision vs pain
        
        Pain
        
        nociceptor
        
        Pain= simpler
        
        less likely to be attached to separate receptor
        
        Vision
        
        often attached to receptor
        
        e.g. rod and cones
        
        light= complex so special receptors r needed
        
        Neural code
        
        temporal patterns
        
        1 more item...
        
        like binary
        
        info sent to brain 4 both
  - - - connect+integrate neurons in region of cns
    - - CNS -> muscle's + glands
    - - From body+ wrld to CNS
- - - - myelinated
        
        Tactile transmission
        
        fast fibres 4 fine sensations
    - - Myelinated
        
        Transmit M+T pain
        
        slow
    - - myelinated
        
        Proprioception
    - - unmyelinated
        
        Also soft comforting sensations
        
        ∴thin+slow
        
        transmit M, T, C Pain
    - - Aδ
        
        first sensation
        
        Fast response in somatosensory cortex
      - C
        
        Second pain
        
        Insula and cingulate
      - Ploner et al 2002
        
        laser as pain stimu
- - - - 2.Grey Matter-> Thalamus
        
        Crosses spinal cord
        
        very long
        
        left stimu= right thalamus activation
        
        Thalamus-> cerebral cortex
        
        (ventrobasal complex)
        
        diff cortices
        
        other brain areas
        
        Hypothalamus
        
        amygdala
        
        3 more items...
- - - - Chronic pain -> fit emotional maps better
        
        acute = sensory maps
        
        ∴whole pain matrix active but moves towards emotional processing as pain becomes chronic
        
        implications
        
        Placebo Analgesia
        
        Wager+Atlas 2015
        
        19 studies
        
        1 more item...
        
        Treatment context
        
        'this will make you feel better'
        
        syringe
        
        eye gaze +body lang
        
        Doctor's office
- - - - thalamus