S17+18 Pain Flashcards
How are nociceptors sensitised?
Tissue damage and inflammation triggers the release of prostaglandins, bradykinin and histamine.
Which type of fibres carry nociceptive information?
Unmyelinated C fibres - polymodal.
Aδ fibres - thermal and mechanical.
Differentiate between first and second pain.
1st: Aδ. Sharp, easily localised, rapid, short, mechanical/thermal.
2nd: C fibres. Dull ache, poorly localised, slow onset, persistent. Polymodal.
What are the spinal connections of nociceptive axons?
Cell bodies in dorsal root ganglion. Up/down short distance in Zone of Lissauer. Synapse onto neurones in lamina I + II : substantia gelatinosa.
Which neurotransmitters are used by pain afferents?
Glutamate. Substance P (most dense in superficial dorsal horn, receptor: NK1).
What are the three ascending pain pathways?
Lateral spinothalamic tract.
Spinoreticulothalamic tract.
Anterior spinothalamic tract.
What is dissociated sensory loss?
Touch, kPa, vibration + proprioception lost on the same side.
Pain lost on opposite side.
How is pain and temperature info carried from the face?
Trigeminal system. Small afferents descend in spinal trigeminal tract to brain stem. Synapse in pars caudalis, ascend contra laterally in trigeminothalamic tract. Projects via ventral posteromedial nucleus.
What is the aetiology of phantom limb pain?
Cortical reorganisation of somatotopic representation in thalamus/cortex.
Central sensitisation - reduction of inhibitory processes in dorsal horn, sprouting of Aβ fibres into lamina I + II.
Name two endocannabinoids.
What do they do?
Anandamide.
2-arachidonyl-glycerol.
Inhibits behaviour response to noxious stimuli, limits hyperalgesia and neuropathic pain.
How do higher brain centres influence pain perception?
Descending pathways from periaqueductal grey and reticular formation decrease transmitter release from primary afferent terminals via opioid receptors.
What are the two defining features of pathological pain?
Hyperalgesia (increased pain sensation).
Allodynia (touch-evoked pain).
What is the gate theory of pain?
Co activation of mechanoreceptors (Aα/β fibres) with nociceptors with suppress activation of the projection neutron by C fibres.
Name five factors associated with changes in pain perception.
Anxiety. Depressed affect. Gender. Circadian variation. Climatic conditions.
How do NSAIDS act?
Side effects? (3)
COX inhibition, decrease in prostaglandin.
GI bleeds, renal toxicity, cardiovascular effects.