41 PAIN Flashcards
Two distinct pain categories
Nociceptive pain and neuropathic pain
Define analgesia
Absence of pain
Define anaesthesia
Absence of sensory stimuli
Define hyperalgesia
Increased response to stimulus that is normally painful
Define allodongia
Response as pain to a stimulus that is not normally painful
What are the factors that nociception depends on
Receptor excitation and inflammatory compounds at area of stimulation.
Transmission to the SC from periphery
Interaction of neurons in SC
Emotional overlay converts nociception to pain in brain
Describe the inflammatory response to tissue injury
Tissue injury causes the release of chemical mediators which can activate nociception. Arachidonic acid- prostaglandins, prostacyclin, thromboxane via Cox enzymes. Also bradykinin and histamine release. Mast cell cause chemotaxis of neutrophils. Platelets aggregate. Sermonic release. Oedema, low pH and pressure increase stimulate nociceptive pain endings.
Name the opioid receptors
Mu1 (analgesia)
mu2 (resp depression)
kappa (sedation and analgesia)
Sigma
What are endogenous opioids and what is their role in the periphery
Endorphins and encephalins. May antagonise glutamate and substance P in the periphery modulating the transmission of pain
Describe modulation in the spinal cord
Inhibitory interneurons (GABA), postsynaptic inhibition through peptide opioids, glycine, noradrenaline, serotonin, and ACh
Describe wind up
Due to modulation in the spinal cord whereby second order neurons fire more that they are supposed to because of persistent partial depolarisation due to modulation. More pain signals transmitted.
Describe supraspinal modulation
When stimulated the midbrain pons and medulla can release serotonin, Ach and noradrenaline to the dorsal horn having an inhibitory effect on pain transmission.
How do triccyclic antidepressants treat chronic pain
Through increased serotonin which inhibits pain transmission
Describe the gate control theory of pain
Mechanorecptors (rubbing, light touch) A beta fibres, synapse with interneurons in the spinal cord which release encephalons, an endogenous opioid which inhibits transmission of c and a-delta fibres (opioids antagonist to glutamate).
