Anatomy and Physiology of Pain Flashcards
*Pain Definition
Pain is an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage.
Purpose of pain
Immediate -> Withdraw from source of injury
Persisting pain -> immobilize to give best chance of healing
Nociception
Neural processes involved in producing sensation of pain
Acute pain
Pain < 12 weeks duration
Chronic
Continuous pain > 12 weeks
Pain that persist beyond the tissue healing time (chronic non-cancer and chronic cancer pain)
Nociceptive pain
Pain that arises from actual threatened damage to non-neural tissue and is due to the activation of nociceptors
Neuropathic pain
Pain caused by a lesion or disease of the somatosensory nervous system.
Tingling, loss of sensitivity
Nociplastic pain
Pain that arises from altered nociception despite no clear evidence of actual or threatened tissue damage causing the activation of peripheral nociceptors, or evidence for disease or lesion of the somatosensory system causing pain.
Allodynia
Pain due to a stimulus that doesn’t normally provoke pain
Dysesthesia
An unpleasant abnormal sensation, whether spontaneous or evoked
Hyperalgesia
Increased pain from a stimulus that normally provokes pain
Hypoalgesia
Diminished pain in a response to a normally painful stimulus
pathway
Peripheral receptor - detect relevant stimulus
1st order neuron - from the periphery to the ipsilateral spinal cord
2nd order neuron - which crosses to the contralateral cord and ascends to the thalamus, the system’s integrative relay station
3rd order neuron - from thalamus to midbrain and higher cortical centers
Nociceptors
Transduction
Physical stimulus –> action potential
Most are poly-modal (thermal / chemical / mechanical)
Primary Afferent Neurones
Nocireceptors are the free nerve endings of primary afferent neurons.
Cell bodies reside in dorsal root ganglion (body)
Trigeminal ganglion (face / head / neck)
