Flashcards in Physiology and Pathophysiology of Pain Deck (39):
what is the 1st step of processing pain?
Transmission to spinal cord (first order neurons)
what is the 2nd step of processing pain?
Transmission to brain (Thalamus) (second order neurons)
what is the 3rd step of processing pain?
Perception, learning, response
what is the 4th step of processing pain?
What is nociception?
The detection of tissue damage by specialized transducers connected to A-delta and C fibers
what are nociceptors?
Free nerve endings of A delta and C-fibres
Respond to thermal, chemical, mechanical noxious stimuli
describe Primary afferents?
Cell body in Dorsal root ganglion
First order neurons
Synapse at spinal cord
what are the 4 different types of Primary afferents?
what neurones receive the input from Rexed lamina 2 and 5?
Low Threshold Mechanoceptive
Wide Dynamic Range
where does the Spinothalamic tract arise in?
Rexed Lamina 2 & 5
what is the Spinothalamic tract ?
Major ascending tract for nociception
sending impulses to thalamus
what is the second relay station in the brain?
where does the Lateral Spinothalamic Tract terminate?
Ventroposterior thalamic nuclei
The medial thalamic nuclei receives input from where?
ventral spinothalamic tract
where does the Ventroposterior thalamic nuclei project to?
where does the medial thalamic nuclei project to?
where does Pain perception occur?
what is the primary control center for descending pain modulation?
describe the defending pathways of pain modulation?
from brain to dorsal horn
Usually decreases pain signal
what is hyperalgesia?
abnormally heightened sensitivity to pain
happens whenever there is tissue injury and inflammation.
what is allodynia?
Decreased threshold for response
what is Spontaneous Pain?
Spontaneous activity in nerve fibres
what is Central sensitization?
It is the response of second order neurons in the CNS to normal input both noxious & non-noxious
what are the three main components of Central sensitization?
what is the main difference between Central sensitization and peripheral sensitization?
central sensitization happens at the level of spinal cord and acts in tandem.
what is wind-up Central sensitization?
Involves only activated synapses
Homosynaptic activity dependent progressive increase in response of the neurons
Manifests over the course of stimuli & terminates with stimuli
what is Classical Central sensitization?
Involves opening up of new synapses (silent nociceptors)
Heterosynaptic activity dependent plasticity
Immediate onset with appropriate stimuli
Outlast the initial stimuli duration
Can be maintained even at low levels of ongoing stimuli
what is Long-term potentiation
Involves mainly the activated synapses
Occurs primarily for very intense stimuli
what is acute pain?
Presence of noxious stimuli
Serves protective function
what is chronic pain?
Pain for 3–6 months or more
Presence of noxious
Does not serve any purpose
Nociceptive, neuropathic or mixed
What is nociceptive pain?
A sensory experience that occurs when specific peripheral sensory neurones (nociceptors) respond to noxious stimuli
What is neuropathic pain?
Pain initiated or caused by a primary lesion or dysfunction in the somato-sensory nervous system
describe nociceptive pain
Pain typically localised at the site of injury – often described as throbbing, aching or stiffness
Usually time limited and resolves when damaged tissue heals
Can be chronic
Tends to respond to analgesics
describe neuropathic pain
pain occurs in the neurological territory of the affected structure (nerve, root, spinal cord, brain)
Almost always a chronic condition (e.g. postherpetic neuralgia [PHN], poststroke pain)
Responds poorly to analgesics
what are some examples of neuropathic pain?
postherpetic neuralgia [PHN]
what drugs are effective when transduction is affected structure?
what drugs are effective when transmission is affected structure?
what drugs are effective when Perception is affected structure?
Cognitive behavioural therapy
Graded motor imagery
Mirror box therapy