Physiology and Pathophysiology of Pain Flashcards
Where is nociception detected and how is it transmitted?
Detected in periphery and transmitted to spinal cord via first order neurons
Where is nociception processed?
In the dorsal horn of the spinal cord
How is nociception transmitted to the thalamus?
Through the brainstem and midbrain via second order neurons
What is mediated in the thalamus?
Perception, learning and response
Pain is modulated via the
descending tracts
Descending pain-modulatory neurons are in the
medulla
Descending pain-modulatory neurons inhibit
nociceptive transmission
Through what mechanisms do descending pain-modulatory neurons inhibit nociceptive transmission?
Direct inhibition of projection neurons
Inhibition of transmitter release from primary afferents
Excitation of inhibitory interneurons
Inhibition of excitatory interneurons
Opioid peptide synthesising cells and opioid receptors are distributed throughout
the pain modulating circuit
Where are endogenous opioid ligans released and what can they produce?
Released at spinal sites
Can produce an analgesic effect
How do endogenous opioid ligans work?
Reduce transmitter release from dorsal horn terminals of primary afferent nociceptors
Direct post-synaptic inhibition of central neurons that are activated by noxious stimuli
Opioid receptor agonists block
excitatory amino acid release from primary afferents
Endogenous opioids also contribute to modulation by inhibiting
neuropeptide release from primary afferents
Ions which provide the energy needed for the transmission of pain signals are transmitted by
sodium and calcium channels
If more receptors are activated and more ions transmitted, what effect will this have on the pain felt?
More pain will be felt
Features of acute pain
Physiological
Presence of noxious stimuli
Serves protective function
Usually nociceptive
Features of chronic pain
Pathological
Presence of noxious stimuli not essential
Does not serve any purpose
Nociceptive, neuropathic or mixed
Nociceptive pain is a sensory experience that occurs when
specific peripheral sensory neurones respond to noxious stimuli
In nociceptive pain, the painful region is typically localised at
the site of the injury
Neuropathic pain is initiated/caused by
a primary lesion or dysfunction in the somatosensory nervous system
Neuropathic pain occurs in
the neurological territory of the affected structure
Treatment options for transduction of pain
NSAIDs
Ice
Rest - immobilise region of pain
Local anaesthetic blocks
Treatment options for transmission of pain
Nerve blocks
Drugs e.g. opiods, anticonvulsants
Surgery e.g. cordotomy
Treatment options for perception of pain
Education Cognitive behavioural therapy Distraction Relaxation Graded motor imagery Mirror box therapy Psychological therapies
Treatment options for descending modulation of pain
Placebos
Drugs e.g. opioids, anti-depressants
Surgery e.g. spinal cord stimulation
