Pain Flashcards
what is pain?
an unpleasant sensory and emotional experience with actual or potential tissue damage, pain is always subjective
what are the five categories for defining pain?
source severity quality extent duration
what are two reasons we need to experience pain?
first we need pain to signal an actual injury or inflammation and second we need pain to highlight underlying malignancy pain
what type of receptors signal pain?
nociceptors and there are many subtypes
what are the two types of primary afferent nociceptors?
a-delta fibres (for sharp shooting pain) and c fibres (for dull aching pain)
what are the nerve endings of nociceptors like?
they are free, meaning the endings are open to the environment
what is primary and second pain?
primary pain sent to NS faster via a-delta fibres and secondary pain takes longer to reach CNS via c fibres
what is hyperalgesia?
an abnormally heightened sensitivity to pain which occurs when painful stimuli increases in intensity and the nociceptors increase their firing rates
what is allodynia?
when pain is caused by a condition that would not normally elicit pain
what are silent nociceptors?
become active following hyperalgesia and allodynia
silent nociceptors form a large reserve pool of pain signalling afferents
what is the main central component of pain pathways?
the dorsal horn within the spinal cord
what does the dorsal horn act as?
a target for a-delta and c fibres, where these nociceptors then release substance p into the dorsal horn
what is substance p?
compound involved in the synaptic transmission of pain signals
an 11 amino acid polypeptide
release requires high levels of firing
what is a dorsal horn ‘wind up’?
occurs during conditions of severe persistent damage, and when c fibres under constant fire. the response of dorsal horn then progressivily builds up
what is gate control theory?
the theory that rubbing an injury that has just occured will alleviate some of the pain temporarily
this is fue to activation of inhibitory interneurons
what are two important pathways with projection neurons?
the spinothalamic pathway and the dorsal column medial lemniscal pathway
how can we overcome pain?
via endogenous mechanisms which begin in the midbrain, PAG perisends projection to medulla and Ralphe nucleu and then spinal cord and dorsal horn, such a process initiates release of serotonin and adrenaline
what is enkephalon?
an inhibitory internueon that releases enkephalin into the area of opiate receptors, it also reduced transmitters that fire action potentials for pain
what are analgesics?
drugs that control pain
what are the four categories of analgesics?
non steroidal anti inflammatory drugs (NAIDS)
morphine-like drugs
local anaesthetics
centrally acting non-opiods
what is aspirin?
an anti-inflammatory medicine based on salicylyic acid
how does aspirin work as an analgesic?
it works by inhbiting the enzyme cyclo-oxygenase (COX) at two stimuli sites: inflammatoy and physiological
what are prostaglandins?
involved in inflammation associated with tissue damage and pain
they are produced by the breakdown of arhidonic acid by the COX enzyme
what is an example of a CNA acting analgesic?
opium
how does opium work?
bind to endogenous opiate receptors designed to dock peptides with opiate like properties, such as endorphins
what are four examples of opiod drugs?
diamorphine codein pethidine fentanyl etorphine
how can we treat opiod dependency?
via methadone maintenance treatment
what are endorphins?
they are opiod peptides and are widely distributed across the brain
what is the future of pain pharmacology in the PNS and the CNS?
cox 2/3 specific inhibitors in the PNS and many targets (including GABAa modulators) in the CNS
what are neurosteroids?
rapid non-genomic steroid effects on GABAa receptors to increase excitation
how does cannabis work?
binds to two endogenous receptors (CB1 and CB2), inducing analgesic properties
what are endocannabinoids?
endogenous lipid based retreograde neurotransmitters that are made on demand and not stored in vesicles
what genetic mutations gives rise to an inability to feel pain?
mutation of the FAAH gene
what are three considerations for the future treatment of chronic pain?
glycine receptor agonists, propofol, and cone snails
