Pain Flashcards
what can pain be defined as
an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or descriebed in terms of such damage
what is normal pain
this is the pain we feel on a day to day basis that is elicited when intense noxious stimuli that threatens to damage normal tissue occurs
why is normal pain an induced pain
only occurs when there is threatened damage to normal tissue
why do we feel normal pain
it has an adaptive biologically useful role becuase it protects us from being harmed - gives us warning of potential damage to our tissues
what characterised normal pain
high threshold with limited duration
what type of pain is normal pain
acute nociceptive pain
what are the sensory afferents involved in acute nociceptive pain
a delta and c fibres
which fibres mediate the perception of all pain
a delta and c fibres
explain this
there are different spikes of activity corresponding to different classes of axons as they conduct action potentials
which axon is responsible for the sensation of dull and aching pain
c fibre
which axon is responsible for the sensation of sharp and stabbing pain
a delta fibres
what is the first pain
sharp and stabbing
what is the second pain
dull and aching
describe the receptive end of nociceptors
unspecialised free nerve endings that give way to a delta and c fibres
describe nociceptor endings
free nerve endings with a high threshold of activation
what does it mean to say that nociceptor endings have a high threshold of activation
it is hard to recruit them but once they are recruited it is clear they have been activated (bruh that is so silly why did i transcribe it like that)
what type of pain is associated with a delta fibres
noxious mechanical and thermal pain
what kind of pain is associated with c fibres
polymodal
what does polymodal mean
responds to various types of stimuli
what kind of receptor proteins are found on nociceptor endings
several types, allowing them to respond to different noxious stimuli
what does it mean to say that nociceptor endings display sensitisation
it means once we have felt a pain in that region of skin, that region will remain sensitive to pain because the nerve endings there are activated
which neuron is in the periphery during the sensory pathway
primary sensory neuron
which neuron is the spinal cord and brain stem during the sensory pathway
the second sensory neuron
which neuron is in the thalamus in the sensory pathway
tertiary sensory neuron
what is the name of the sensory pathway for somatic nociception
spinothalamic pathway
what is the official name for pain
somatic nociception
what stimuli results in the spinothalamic pathway being activated
pain
temperature
crude touch
relay the full spino thalamic pathway to me
- free nerve endings transduce noxious stimuli
- depolarise nerve endings
- conduct an action potential to the spinal cord
- via a delta or c fibres
- into outer layer of the dorsal spinal cord
- synapse with second order sensory neurons
- axons cross over to opposite side of the spinal cord and project up via the anterolateral funiculus
where are the axons of second order neurons found as they relay information up the spinal cord to the thalamus
in the anterolateral funiculus - a well defined region of white matter
where is the antero funiculus
as the second order neuron ascends the spinal cord, it gives off branches. where, and how many?
2 at the medulla
2 at the pons
2 at the midbrain
2 at the thalamus
why do the second order sensory neurons give off branches as they ascend
to activate neuronal populations in the pons and medulla to aid with the perception of pain
what is the spino thalamic tract
a sensory tract that carries nociceptive, temperature, crude touch and pressure from our skin to the somatosensory area of the thalamus.
the lateral spinothalamic tract carries pain and temperature.
the anterior spinothalamic tract carries sensory input about crude touch
where in the spinal cord do the primary afferents synapse with the secondary afferents
substantia gelatinosa, located in the grey matter of the spinal cord
describe the route of the second order sensory neurons
they enter the anterolateral portion of the spinal cord and enter the brainstem as the spinal lemniscus
what makes us itch
pruritogens
describe the nociceptive afferents in the tooth
similar to the spino thalamic pathwawy, the free nerve endings are found extended in dentine and will send their axons via the trigeminal nerve into the ventral trigeminothalamic pathway to the somatosensory cortex in the appropriate somatotopically defined regions
summarise the ventral trigeminothalamic pathway
- information is projected along the trigeminal primary afferent into the spinal nucleus of the spinal cord
- synapses with second order neuron
- crosses midline and projects to the thalamus
- synapse with third order neuron
what are the receptors of the pain pathway
nociceptors free nerve endings
what is the axon class of the pain pathway
a delta and c fibres
what are the central nervous system relay cells in the pain pathway
spinal dorsal horn and the spinal trigeminal nucleus
what is the central nervous system pathway for pain pathways
spinothalamic for body and ventral trigeminothalamic for face
which area in the forebrain is involved in pain pathways
primary sensory cortex and subcortical areas
where are the target neurons found in the pain pathway
dorsal horn or the spinal trigeminal nucleus
why is pain a good thing
it is a prominent symptom and is good for diagnosis usually
what does pain attribute for diagnosis
- location
- quality
- intensity
- duration
- relieving events
what does the location of pain aid for in diagnosis
it identifies the certain spinal cord regions involved via the use of a dermatome map
it can also locate which branch of the trigeminal nerve is being stimulated depending on where in the face the pain is being felt.
which branches of the trigeminal nerve are sensory
opthalmic and maxillary branch
which branch of the trigeminal nerve is both sensory and motor
mandibular branch
why can location of pain be misleading
due to referred pain
what is referred pain
this is when pain is perceived in one part of the body but the pathology is elsewhere
why is referred pain believed to occur
due to sites being of common embryological origin
how does referrred pain come about
pain tenders to refer from an internal organ to a superficial area like the skin
why does pain referral happen
convergence of inputs in the central nervous system
where is pain felt when the heart is pathological
the left arm and shoulder
where is pain felt when the oesophagus is pathological
sternum and left shoulder
where is pain from the ureter felt
around the pelvic region
is pain the same for everyone
no, everyone has different thresholds for pain
what are some factors for pain perception
genetic
molecular
cellular
anatomical
physiological
psychological
social
what is SCN9A
this is the gene that encodes that alpha subunit of voltage gated sodium channel Nav1.7
which type of sodium channel is associated with nociceptive afferents
Nav1.7
what does mutation in SCN9A result in
loss of NAv1.7 function, leading to an inability to experience pain
the sensory and motor tests of the patients with this mutation remain normal
what are the three main factors that can impact how noxious stimulus is perceived
psychological
situational
emotional
what are the psychological factors that lead to a change in perception of what noxious stimulus was applied
sex
age
cognitive level
previous pains
family
culture
what are emotional factors that can affect how we perceive pain
fear
anger
frustration
what are situational factors that can impact how we perceive pain
expectation
control
relevance
describe the gate control theory of pain
this is the idea that when we feel pain if we shake our hands or rub the pain then it will dissipate
why does rubbing or shaking a wound dissipate the pain
rubbing the injury stimulates beta fibres, and these axons project into the spinal cord.
they birfurcate to send the principle branch to the dorsal column nuclei, where they activate the dorsal column pathway to allow perception of the rubbing stimulus
another branch will activate circuits in the dorsal spinal cord that activates a population of inhibitory interneurons which inhibit the second order pain projecting neurons.
inhibiting these neurons blocks transduction which loses the perception of pain.
information is relayed into the spinal cord, and rubbbing engages the inhibiting interneurons to inhibit the perception of pain
what do the collateral branches of the second order neuron function to do
they engage a series of neurons that send information back down the spinal cord to influence the perception of pain in the spinal cord itself
why are there collateral sstems in the descending projections of the spinal cord
they modulate the perception of pain so we try to dampen it down
what is the supraspinal loop
this is when there is direct inhibition of projection neurons and activation of enkephalin containing interneurons that reduce the activity in nociceptive circuits
describe the events in the supra spinal loop
activity can be dampened down in the dorsal horn.
release of seratonin and noradrenaline in stressful situations can lead to inhibited second order projections which reduces the activity of nociceptor circuits in the region
what is the 5HT projection
this is seratogenic
what is the NA projection
noradrenaline
where do 5HT and NA come from
the PAG and the medullary raphe nuclei
what is PAG
periaqueductal gray matter
where is the PAG found
in the pons
where is the medullary raphe nuclei
the medulla
why do we have a supra spinal loop
to allow us to continue a situation where we are injured if there is danger or high levels of excitement - we do not notice the pain we are in nearly as much
what are the cardinal signs of inflamation
heat
redness
swelling
pain
loss of function
what is the triple response reactiona
this is when we scratch ourselves, and there is a red reaction, a wheal and a flare
what is the red reaction
the redness directly where the injury occurred
what is the wheal
this is the white border that occurs around the injury
what is the flare
this is the red concentration encasing a wound on the surface
what is the triple response a result of
mild mechanical trauma
what is dermatographia
people with strong triple responses that can have prominent reactions to scratches that last a long time
what are the chemicals released at the sight of mechanical trauma
potassium ions and prostaglandings
brady kinin
5-HT
what is released from damaged tissue after mild mechanical trauma
potassium ions and prostaglandins
what is released from plasma when a capillary is ruptured due to mild mechanical trauma
bradykinin
what is released from platelets when there is mild mechanical trauma
5-HT
what is the purpose of the release of potassium ions, bradykinin, prostaglandins from a trauma
they activate receptive endings to notify that there was tissue damage, which leads to depolarisation and generation of an action potential that is conducted centrally to engage in the spino thalamic pathway
what are some substances that arrive to the site of infection
peptides from other free nerve endings like CGRP and substance P, which mediate the triple respone
there is also mast cells activated to release histamine to further activate receptive endings
what causes the production of a wheal
substance P can cause plasma exctravasation through the release of bradykinin which is important for wheal generation
why does a flare develop in the triple response
CGRP causes vasodilation and this happens peripherally which is why the flare develops
what are relieving factors for the triple response
restriction of blood pressure
apply cold water to vasconstrict
take antihistamine to reduce mast cell degranulation and reduce triple response
which substance produces the wheal
bradykinin
what are the roles of substance P
plasma extravasation
oedema
release of bradykinin
what are the roles of CGRP
dilation of blood vessels to produce the flare
which drug can minimise the effect of mast cell degranulation
antihistamines
