pain and analgesics 1 Flashcards
define pain
pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage
it is a perception that occurs in the brain caused by the activation of nociceptors by thermal, mechanical, chemical or other stimuli
what are the types of nociceptive pain? how can they be divided?
cam be divided into visceral pain and somatic pain, referred pain, radiating pain, breakthrough pain, psychogenic pain, phantom pain
what is visceral pain?
is diffuse, difficult to locate, and often referred to a distant, superficial structure
what is somatic pain?
superficial pain: activation of nocieptors in the skin or other superficial tissue; sharp or burning, well defined
deep somatic pain; activation of nociceptors in ligaments, bones, tendons, fasciae, muscles, dull aching, poorly localized
what is referred pain?
perceived at a location other than the site of the painful stimulus
what is radiating pain?
pain that spreads from the original area outwards to another part of the body
what is breakthrough pain?
is a transitory flare up of pain against a background of otherwise well controlled pain
what is psychogenic pain?
result of some underlying psychological disorder
what is phantom pain?
refers to a patient’s experience of pain in a part of the body that has been removed surgically or traumatically
what is neuropathic pain?
pain that follows direct injury to a peripheral nerve
how is neuropathic pain characterised?
partial or complete damage to or dysfunction of the somatosenory pathways in the PNS AOR CNS and
the occurance of pain and hypersensitivity phenomena within the denerated zone and its surroundings
who is neuropathic pain observed in?
diabetics and in carpal tunnel syndrome or sciatica
following traumatic injury, inducing ischemia, radiation therapy, excessieve alcohol consumption, immune system disease, coeliac disease or viral infection
what are the different types of diabetic neurpathic pain?
peripheral- sensory neuropathy- feet/legs
autonomic- results from damage to nerves which controls involuntary functions
focal neuropathy- results from injury to a peripheral nerve at one site
what is neuropathic pain insensitive to?
morphine and other opioid drugs
how can neuropathic pain be significantly relieved?
TCA- Amityuptyline
anticonvulsant agents- carbamazepine
corticosteroids- dexamethasone- may produce substantial improvement in some cases in neurpathic pain associated with cancer
what is trigeminal neuralgia?
is a neuropathic facial pain condition
- pain/ loss of sensation in the face
- severe paroxysmal, lancinating facial pain
- triggered by innocuous stimuli
- a disorder of the 5th cranial nerve
what is the trigeminal nerve?
it is the 5th and largest of the 12 pairs of crianial nerves
the chief nerve of sensation for the face
contains sensory fibres for the face, as well as a motor segment important for mastication- chewing
what does the trigeminal nerve divide into?
3 brances:
1- ophthalmic division- V1- provides sensation to the forehead and eye
2-maxillary division-v2- provides sensation to the cheek, upper lip and roof of the mouth
3- mandibular division-V3- provides sensation to the jaw and lower lip
what are the treatments for trigeminal neuralgia?
carbamazipine
alt: oxcarbazepine, gabapentin, phenytoin, baclofen, amitryptyline
what assessment tools are there for pain?
wide range. these are grouped into categories: uni-dimensional and multi-dimensional methods
what are the uni-dimensional assessment tools?
VAS VRS NRS graphic rating scales verbal descriptor scales body diagrams computer graphic scales picture scales
what are some multi-dimentional assessment tools?
McGill pain questionnaire bried pain invintory west-haven- yale treatment outcomes pain inventory behavioural pain scales pain disability index pain information and beliefs questionnaire
what does pseudo-unipolar mean?
a neuron, which means they have a single axon extending from the cell body that forms two extensions: the dendrites and the axon- most sensory neurons
how are sensory receptors classified?
sensory receptors are classified into different categories based on their structure, location and type of stimulus
what are some types of sensory receptor classificatins?
chemoreceptor, mechanoreceptor, photoreceptor, thermoreceptor. nociceptor
what is a nociceptor?
it is a sensory receptor that detects a wide range of stimulus modulates
different chemical or physical stimuli can excite nociceptors by activating a single receptor
what do nociceptors release?
they are excitory neurons and release glutamate as their primary neurotransmitter
what threshold does a nociceptor have?
elevated stimulated threshold
encode the intensity of a stimulus within the noxious range i.e. it must not saturate when a stimulus reaches noxious levels
what are the different types of nociceptors?
thermal nociceptors, mechanical nociceptors, chemical, polymodal, silent
what is the ascending pathway?
refers to the neural projections by which sensory information travels the periphery to the brain
what are the major ascending pathways?
the dorsal column: first order neurons consist generally of AA and Ad fibres
spinothalamic tract: the laterla ad and C fibres and the anterior spinothalamic tract Ab fibres
the spinocereballar tract
how do the neurons act in the pain pathways?
1st order neurons- signals from the periphery to the spinal cord or to the medulla
2nd order neurons- signals from the spinal cord or medulla to the thalamus
3rd order neurons- signals from the thalamus to the primary sensory cortex
what do the 1st order neurons do in the ascending pathway?
a sensory stimulus is signalled simultaneously via- fast-conducting Aa or Ab fibres
slow conducting C and Ad fibres
what do the second order neurons do in the ascending pain pathway?
form the ascending spinothalamic tract, which projects tonuclei in the medualla and midbrain on the way up to the thalamus. from thethalamus, the signal is carried by 3rd order neurons
what do the 3rd order neurons do in the ascending pathway?
with their cell bodies in the thalamus, project to the somatosensory cortex and to limbic cortical areas
what does PAG project?
PAG projects from the anteriour cingulate.
to the RVM and DLPT which send desceding path modulatory projections back to the afferent pathways
what is the role of the descending pain pathway?
modulates pain sensation with by enhancing or inhibiting the conduction of pain
what does the descending pain pathway include?
anterior cingulate and insular cortex
periaqueductal gray
nuclei in the amygdala and pvg of the hypothalamaus
DLPT and RV,
WHAT neurotransmitters are involved in the descending pain pathway?
opididergic noradrenergic serotonergic cholinergic GABA-ergic endocannabinoids
what does PAG receive/ send projections to?
recieves: anterior cingulate, insular, prefrontal cortex, hypothalamus, amygdala and nucleus accumbens
sends: dlpt and rvm
what are the neurotransmitters involved in the descending pathway?
opioids, NA, GABA ,ACH, endocannabinoids
what is the spinal chords role in descendinh pain pathway?
recieves imput from the RVM
- 5ht release
hyperpolarisation of ascending fibre and dorsal horn projection with 5HT1 receptors
depolarisation of spinal GABAergic internueons with 5HT2A, 5ht3 receptors
what happens when the spinal chord recieves imput from DPLT?
- adrenergic cell clusters in the rostral medulla oblongata
noraderergic nuclei is the locus coreuleus abd sub-coereus regions
hyperpolarisation of projection neurons when interacting with a2A repectors
hyperpolarisation of primary afferent fibres with a-2B/C receptors
depolarisation of dorsal horn inhibitory interneuons via a-1A receptors
how does 5HT release occur in the descending pathway?
hyperpolarization when interact with 5-HT1 R
depolarization when interacts with 5HT2 R or 5HT3 r
how is NA released in the descending pathways?
hyperpolarisation of projection neurons when interact with a-2A R, and of sensory nerons when interacts with a-2B/C
depolarisation of forsl horn inhibitory of interneuorns via a-1A r
