Pain - Physiology to Pharmacology Flashcards
how does affective (emotional) states influence the magnitude of pain experience
presentation of negative pictures caused a decrease in pain tolerance (positive pictures had opposite effect)
what are the different descriptors of pain
1-3 = temporal descriptions
- acute
- chronic
- intermittent
4-5 = neurobiological descriptions
- inflammatory
- neuropathic
6-7 = spatial descriptions
- visceral
- somatic
what is physiological pain
pain proportional to intensity of noxious stimulus
protects againts further injury
what is pathological pain
pain greater than apparent noxious stimulus
detrimental
ex. phantom limb pain
what is the pain pathway
- nociceptor generates an action potential (transduction)
- afferent fibre: conducts action potential to CNS (transmission)
- spinal cord: processing occurs at the level of the dorsal horn (modulation)
- brain: conscious experience of pain
what are the areas in the brain involved in pain perception
- primary and secondary sensory cortex
- thalamus
- midbrain
- pons
- brainstem
what is nociception
detection of noxious stimuli that actually or potentially cause damage to organism
what do nociceptors respond to
- intense mechanical deformation
- potentially damaging temperatures
- noxious chemical stimulation
what do C fibres respond to
- tissue damaging stimuli
- sharp blow
- damaging heat
- chemicals released by mechanically damaged tissue (inflammation)
are C fibres myelinated or unmyelinated
unmyelinated
are C fibres slow or fast conducting
slow
do C fibres respond to dull or sharp pain
dull burning pain
are C fibres large or small diameter
small
are A fibres large or small diameter
large
are A delta fibres myelinated or unmyelinated
unmyelinated
are A delta fibres short or fast conducting
fast conducting
do A delta fibres respond to dull or sharp pain
sharp pain
what are A delta fibres activated by
stimuli that produce strong shearing force in skin (cut, strong blow, tug on a hair)
what are the inhibitory influences in the pain perception
- descending inhibition: descending pathways from periaqueductal grey (PAG) and rostral ventromedial medulla (RVM) contain endogenous opoid pathways –> project to dorsal horn to reduce transmission
- gate control: activation of AB fibres with tactile, non-noxious stimuli activates inhibitory interneurones in the dorsal horn –> rubbing alleviates pain
what is peripheral sensation
inflammatory mediators (PGs, increase nociception activation)
what is central sensation
repetitive nociception input enhances transmission at level of dorsal horn (NMDA receptor)
what is hyperalgesia
an increased response to a stimulus which is normally painful
primary or secondary
what is allodynia
pain due to a stimulus which doesn’t normally provoke pain
what occurs during continuing or repeated stimulation of nociceptors
become increasingly reactive (hyperexcitable) with continuing or repeated stimulation
sensation of peripheral nociceptors so that they transmit an amplified signal to the spinal relay centre
chemically mediated
what is central sensitization
over activity of second-order neurons in the dorsal horn leads to enhanced pain transmission
associated with changes within and between neurons
can be transitory or permanent
what is analgesia
absence if pain or a reduction in intensiry of pain perceived
what are analgesic drugs
local anaesthetics
opioids
non-steroidal anti-inflammatory drugs
alpha 2 adrenoceptor agonists
ketamine
nitrous oxide
what are non-pharmacological methods do reduce pain
nursing care
physiotherapy
acupuncture
transcutaneous electrical nerve stimulation (TENS)
where are the sites of drug action
- brain: sensory cortex (opiods interfere with central conscious perception of pain)
- spinal cord: dorsal horn (opioids & alpha 2 agonists modulate neurotransmission
- afferent fibre: local anaesthetics inhibit transmission
- nociceptor: NSAIDs reduce production of inflammatory mediators
what is preventative analgesia
admin of analgesic drugs throughout the perioperative period
to prevent or limit the development of sensitization induced by pre-, intra- or post-operative noxious stimulation
what is multimodal analgesia
use of a combination of drugs that act at different points in the nociceptive pathway
more effective analgesia with fewer adverse effects
