Spinal Mechanisms - Lecture notes Anatomy Notes PDF

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Spinal Mechanisms

Lissauer’s tract Substantia gelatinosa- Rexed’s lamiae Glutamate & substance P Ascending pathways

Perception of pain:

  

Subjective Variable Multi- dimensional- sensory, affective, cognitive

We have endogenous analgesic systems that work to modulate pain signal Afferent modulation of pain —> gate control theory of pain

Simultaneous activity in low threshold mechanoreceptors can inhibit onward passage of nociceptive signal Theory: The large diameter mechanoreceptors & nociceptors activate the same projection neurone. Simultaneous activity of both these afferents will surpress/ dilute the nociceptive signal.

 Transcutaneous electrical stimulation (TENS) - Relief of pain - May interrupt pain signals travelling up spinal cord - May stimulate descending control systems. We have endogenous analgesic systems built in nervous system - Regulate gain of pain system - Fulfils survival role Central analgesic system: Electrical stimulation evoked analgesia: - From midbrain & pontine sites - Via inhibition of spinal & sensory neurones Chemical activation (or disinhibition) of specific areas - Revealed regional specificity eg periaqueductal grey Deep brain stimulation: - Rare specific refractory pains - Aim for PAG, PVG/ Can produce selective analgesia

Descending control systems    

Hypothalamus Peri-aqueductal grey (PAG midbrain) Rostral ventromedial medulla Dorsolateral pons (locus coeruleus, A7, A5)

Desceding pathways INHIBIT projection neurones in the dorsal horn via DIRECT & INDIRECT (interneurone) pathways....