Overview of Pain Medication Flashcards
Is pain a stimulus?
No, it is a sensory and emotional experience
Describe the basic four stages of pain sensation
- Periphery
Nociception
Transmission to spinal cord (first order) - Spinal Cord
Processing
Transmission to the brain (thalamus, secone order) - Brain
Perception, learning, response - Modulation
Descending tracts
Briefly define nociception
The detection of tissue damage by specialised transducers connected to A-delta and C fibres
Where are the cell bodies of primary afferent neurons?
Dorsal root ganglion
Where do first order afferent neurons synapse?
In the spinal cord at the level at which they enter
Are A-alpha and A-beta fibres myelinated?
Yes
Are A-delta fibres myelinated?
Yes but lightly
Are C fibres myelinated?
No
In what areas of the spinal cord do the primary afferent neurons synapse?
Rexed lamina 2 and 5 of the ventral horn of the grey matter, the Substantia Gelatinosa
From where in the spinal cord do second order afferent neurons travel upwards to the brain?
The posterioventral part of the cord on the contralateral side of entry in the white matter spinothalamic tracts
Where in the brain does pain perception occur?
The somatosensory cortex
Are the receptive neurons in the spinal dorsal column nociceptive specific?
Yes
Is the threshold of the pain sensing neurons in the spinal dorsal column high or low?
Low
What is the major ascending tract for nociception?
Spinothalamic tract
With which areas is the thalamus connected?
Cortex
Limbic system
Brainstem
Where in the spinal cord does descending efferent information travel?
In the periaqueductal grey matter
What is allodynia?
A decreased threshold for nociceptive response
What is hyperalgesia?
An exaggerated response to normal and supranormal stimuli
What causes spontaneous pain?
Spontaneous activity in the nerve fibres
What is central sensitization?
The response of second order neurons in the CNS to normal input both noxious and non-noxious
What are the three main components of central sensitization?
Wind-up
Classical
Long-term potentiation
Describe the wind-up component of secondary sensitization
This involves only activated synapses and is dependent on homosynaptic, it results in a progressive increase in the response of the neurons
It manifests over the course of the stimuli and terminates with stimuli
Describe the classical component of secondary sensitization
This involves the opening of new synapses that depend on heterosynaptic activity. When the appropriate stimuli there is an immediate response that outlasts the initial stimuli duration
Describe the long-term potentiation component of secondary sensitization
This involves mainly the activated synapses - persistent strengthening of synapses based on recent patterns of activity and occurs primarily for very intense stimuli, often chronic pain
What are the criteria for chronic pain?
Pain for 3-6 months or more
Pain beyond expected period of healing
Usually has no protective function
Degrades health and function
Outline acute pain
Usually obvious tissue damage increased Increased nervous system activity Pain response upon healing Serves a protective function
Is a noxious stimulus always present in acute pain?
Yes
Is a noxious stimulus always present in chronic pain?
Not essential
Does chronic pain have any purpose?
No
Is acute pain pathological or physiological?
Physiological
Is chronic pain pathological or physiological?
Pathological
What are two main forms of ‘pain’?
Nociceptive
Neuopathic
Describe neuropathic pain
Pain initiated or caused by a primary lesion or dysfunction in the somato-sensory nervous system
Almost always a chronic neuropathic condition
Responds poorly to conventional analgesics
Describe nociceptive pain
A sensory experience that occurs when specific peripheral sensory neurons (nociceptors) respond top noxious stimuli
The pain in usually localized at the site of the injury and typically resolves when the damaged tissue heals
Can be chronic e.g. osteoarthritis
Tends to respond to conventional analgesics
How do pain and nociception differ?
Pain is the subjective phenomena in response to the physiological process that is nociception
What stage of nociception do NSAIDs, ice and rest target?
Transduction
What stage of nociception do nerve blocks, opioids, anticonvulsants and some forms of surgery target?
Transmission
What stage of nociception do education, cognitive therapy, distraction, relaxation etc target?
Perception
What stage of nociception do placebos, opioids, antidepressants, and surgical spinal cord stimulation target?
Descending modulation
