Physiology of pain Flashcards
NOCICEPTIVE PAIN
i) what is it? name three types of stimuli
ii) which two types of fibres are stimulated?
iii) what does it reflect?
iv) is it typically reversible or irreversible?
i) physiological response to real or threatened non neuronal tissue damage (it is a normal and adaptive response)
- thermal, chemical, mechanical stim
ii) stim of nociceptors on peripheral nerves - C fibres or Adelta fibres
iii) reflects normal adaptive func of somatosensory nervous sys
iv) typically reversible - subsides when stim is removed
TYPES OF NOCICEPTIVE PAIN
i) name three places where nociceptors are stimulated in somatic nociception? which type of fibres are impulses transmitted along?
ii) what type of pain is somatic pain? what is it exacerbated by?
iii) where are nociceptors activated in visceral nociception? what type of fibres is pain transmitted along?
iv) name two things that may cause visceral noci? is it well or poorly localised? name two symptoms it may be associated with
i) somatic - activ of noci in skin, muscles, bones, joints
- transmit along A delta or C fibres
ii) somatic is sharp or dull and exacerbated by movement
iii) visceral - nociceptors in internal organs
- transmitted along autonomic fibres (can cause confusion about source)
iv) visceral - caused by distention or ischaemia
- assoc with nausea, vomiting, sweating
INFLAMMATORY PAIN
i) what is it?
ii) what happens in the periphery? what two effects does this have on local noci?
iii) how quickly to changes to nociceptors occur? name two things that can cause this type of pain?
i) response of the somatosensory nervous sys to tissue damage and inflammation
ii) periphery - increased inflam mediators > sensitise local nocis
- lowers threshold for responsiveness (periph sens)
- activation of pathways after innoc input and exaggerated response to noxious stim
iii) changes can occur in minutes
- surgery and tissue trauma can cause this
NEUROPATHIC PAIN
i) what is it? what does it result in?
ii) what is allodynia?
iii) what is hyperalgesia?
iv) what is hyperpathia?
v) give three things that neuropathic pain may feel like?
i) NP pain is a lesion or disease of the somatosensory NS
- impacts on func and causes struc changes > sensory loss and inc responsiveness to noxious and innocuous stimuli
ii) allodynia - pain after non painful stim
iii) hyperalgesia - heightened pain after painful stim
iv) hyperpathia - eruptive pain extenting beyond duration of stim
v) electric shock, burning, cramping
MANAGEMENT OF NEUROPATHIC PAIN
I) give three examples of neurpathic pain
ii) what is there loss of?
iii) is paracetamol effective?
i) diabetic peripheral neuropathy, sciatica, phantom limb pain
ii) loss of normal inhib func at level of spinal cord
iii) no
VASCULAR DISEASE
i) what three pain mechanisms is it a combination of?
ii) which two neurons is there cross talk between?
iii) is it hard or easy to treat? what do patients often develop?
i) combo of nociceptive, inflammatory and neuropathic mechanisms
ii) cross talk bet sensory neurons and sympathetic NS
iii) hard to treat > develop chronic pain state
NOCICEPTION
i) is it the same thing as pain? how is it described?
ii does rate nociceptors fire match pain intensity?
iii) what level of myelination do Group A, B and C neurons have?
i) different to pain - how signals about possible tissue damage get from the site of injury to the brain
ii) no
iii) Group A - heavily myelinated,
Group B - moderately myelinated
Group C - unmyelinated
TYPES OF NERVE FIBRE
i) are A delta fibres myelinated? what type of info do they carry?
ii) are C fibres myelinated? what type of info do they carry?
iii) which type of nerve fibre carries proprioceptive information?
iv) which nerve fibre conducts the fastest
v) which fibre is responsible for sharp initial pain? what is responsible for dull pain later?
i) a delta are myekinated and carry pain (mech and thermal) info
ii) C fibres are non myelinated and carry pain (mech, therm, chem)
iii) A alpha carry proprioceptive info
iv) a alpha conduct the fastest
v) sharp initial pain = a delta
dull pain later = c fibre
SPINAL CORD
i) which area is the first relay station?
ii) after synapsing with which order neuron does it decussate in the spinal cord?
iii) what tract does it then descend in?
i) DRG is the first relay station
ii) synapse with second order neuron then decussate
SYNAPSES
i) what are the layers of grey matter called in the dorsal horn?
ii) which layers do they A delta fibres terminate in? (2) what do they synapse with directly?
iii) which layer do C fibres synapse in? what is this aka?
iv) what can C fibres also synapse indirectly via?
v) after crossing - name two tracts do the second order neurons asc in?
i) rex laminae
ii) A delta synapse in layers 1 and 5
- synapse with second order neurons
iii) lamina 2 aka substansia gelatinosa
iv) C fibres can also synapse indirectly via interneurons
v) 2 order neurons asc on spinothalamic and spinoreticular tracts
SPINOTHALAMIC TRACT
i) where does it ascend? where does it terminate?
ii) what aspect of pain is felt in the lateral - neo ST tract?
iii) what aspect of pain is felt in the medial - paleo ST tract?
i) ascends anterolaterally in white matter and terminates in the thalamus
ii) sensory-discriminative aspet of pain felt in lateral
iii) autonomic/unpleasant emotional component of pain felt in medial
SPINORETICULAR TRACT
i) where does it terminate?
ii) where does it project diffusely to?
iii) what does it promote?
iv) what is the second relay station in the brain?
i) terminates in reticular formation of medulla and pons
ii) projects diffusely to cerebral cortex
iii) promotes behavioural arousal
iv) thalamus is second relay station
PERCEPTION OF PAIN
i) where do third order neurons project from and to?
ii) what system to 3rd order neurons project to to help create perception of pain?
i) 3 o from thalamus to somatosensory cortex
ii) 3o to limbic system
LIMBIC SYSTEM
i) where is the insula located? which type of inputs come in here? what does it assess?
ii) what is the function of the anterior cingulate cortex in relation to pain (2)
iii) name three brain areas that the ACC connects to
i) insula is located deep within the lateral sulcus
- visceral nociceptive inputs
- asess stim intensity
ii) ACC assoc with attention and response to pain
iii) ACC connects to amygdala, hippocampus and hypothalamus
GATE CONTROL THEORY
i) what type of input ‘closes the gate’ to nociceptive input
ii) what type of fibre causes inhibitory interneurons to close the gate? what does this mean for when an impulse from a C fibre arrives?
iii) what does closing the gate ultimately prevent
iv) what action can close the gate?
v) do C fibres activate or inhib the inhibitory interneurons
i) non painful inputs
ii) A beta causes inhib INs to close the gate
- means that C fibres cant synapse to second order neurons to pass on pain info
iii) closing the gate prevents the AP from travelling to the CNS
iv) rubbing the skin can activate A beta fibres anc close to the gate by activating inhibitory interneurons
v) C fibres inhibit inhibitort INs
