Flashcards in Pain Deck (17):
What is the difference between nociception and pain?
Pain is the perception of nociception and requires its relay to the cortex
What are the 2 broad classifications of pain? Give 2 specific examples of each type
Adaptive/protective (e.g. nociceptive pain, inflammatory pain)
Maladaptive/pathological (e.g. neuropathic pain, functional pain syndromes)
Describe the pathway for transmission of nociceptive pain
Input from noxious stimuli (e.g. heat, cold, intense mechanical force, chemical irritants) is carried to the spinal cord via unmyelinated C fibres or myelinated AD fibres
Fibres synapse with 2nd-order neurons in different layers of the dorsal horn dependent on the type of fibre type
~5-10% of 2nd-order neurons cross via the anterior white commissure to project to the brain in the anterolateral tract; others form circuits ipsilaterally (e.g. for spinal reflexes)
May produce pain, autonomic response and withdrawal reflex
What is TRPV1?
A nociceptive transducer and the receptor for capsaicin
What is the mechanism underlying nociception in inflammatory states?
Inflamed or damaged tissues release nociceptor sensitisers (e.g.IL-6, TNF-A, H+), resulting in a pain response to low- and high-intensity stimuli
What are the different effects of peripheral and central sensitisation?
Peripheral sensitisation results in any stimulation of the peripheral nociceptor (innocuous or noxious) producing primary allodynia or primary hyperalgesia, due to the sensitivity of the receptor
Central sensitisation produces secondary allodynia where an innocuous stimulus stimulates a low-threshold neuron, and secondary hyperalgesia where a noxious stimulus stimulates a nociceptor, due to the sensitivity of the central pathway
Name 4 different types of nociceptor. How do they differ?
Peptidergic (secrete proteins; polymodal)
Distinguish between allodynia and hyperalgesia
Allodynia: a painful response to a normally innocuous stimulus
Hyperalgesia: an increased response to a normally painful stimulus (in secondary hyperalgesia the area of sensitivity may expand outside the damaged region)
What is the abnormality in neuropathic pain?
Peripheral or central neural lesion or disease
Describe 5 ways peripheral neural lesions may cause maladaptive, low-threshold pain
Increased axonal sensitivity to stimuli, producing ectopic transduction
Sympathetic-sensory neuron coupling
Ectopic action potential generation
Neuronal cell death
Altered synaptic transmission and central sprouting
Give some examples of peripheral and central causes of neuropathic pain
PNS: nerve trauma, toxic and metabolic neuropathies, HZV, AIDS
CNS: stroke, spinal cord injury, MS
List 3 conditions causing dysfunctional, maladaptive pain due to abnormalities in central processing
Migraine, pelvic pain conditions, fibromyalgia
List 7 drugs which can induce analgesia
How do analgesic drugs work?
By activating the periaqueductal grey pathway (projects to dorsal horn of spinal cord to inhibit the transfer of pain-related information)
How does the spinal cord modulate pain?
Inflammation produces negative feedback which modulates transmission of nociceptive information in the spinal cord
How does the fear response induce hypoalgesia? What cortical areas are involved?
Via the top-down psychological modulation of pain
Involving the anterior cingulate, PFC and insula