Pain Flashcards
What is the adaptive role of pain and what are it’s characteristics?
protective function
high threshold and limited duration
What fibres mediate pain?
a-delta fibres and C fibres
What type of pain are a-delta fibres associated with?
sharp stabbing pain
What type of pain are C fibres associated with?
dull, aching pain
What are characteristics of nociceptor endings?
free nerve endings
high threshold of activation
What are polymodal responses in C fibres?
can respond to various types of pain - itching, mechanical, heat, and crude touch
What stimuli do a-delta fibres respond to?
mechanical
heat
crude touch
What kind of touch can pain receptors transmit?
crude touch
fine touch is for DCML
Where do the axons cross over in the spinothalamic pathway?
antero-lateral funiculus
In which pathway are the spinal lemniscus found?
spinothalamic pathway
In the spinothalamic pathway, the ascending projection up to the thalamus is called?
spinothalamic tract
Where do fibres terminate in the brain?
somatosensory cortex
What are the attributes of pain?
- Location
- Pain quality – sharp stabbing, dull ache
- Pain intensity
- Frequency / duration
- Provoking / relieving events
Why is the location of the pain important?
dermatomes can help locate damage to spinal regions or branches of trigeminal nerve
What is referred pain?
These are perceived in one part of the body, but the pathology is elsewhere
Where does referred pain come from?
Pain tends to refer from an internal organ to a superficial area e.g. skin
Referral due to a convergence of inputs in the CNS
Where can pain from the heart be felt?
left shoulder, and forearm
Where can pain from oesophagus be felt
left shoulder and forearm
What does a mutation of SCN9A gene cause?
loss of NAV1.7 function
inability to experience pain
however sensory and motor tests normal
What 7 factors can influence pain perception?
Genetic
Molecular
Cellular
Anatomical
Physiological
Psychological
Social
What can rubbing the painful area activate?
a- beta fibres through mechanoreceptors (DCML)
What does the bifurcation of the a-beta fibre activate?
activate inhibitory inter-neurones
What do inhibitory inter-neurones inhibit?
2nd order projecting pain neurones
What are the descending projections able to do?
inhibits projection neurones
What composes the triple response to mechanical trauma?
wheal (swelling)
redness
flare
What is an increased triple response disease called?
Dermatographia
What mediators can release upon mechanical trauma?
potassium
prostaglandins
serotonin
bradykinin
platelets
What does the release CGRP and substance P cause?
activation of mast cell to release histamine
What does histamine do?
vasodilation, redness
What does the release of bradykinin cause?
wheal (swelling)
What does the dilation of blood vessels cause?
flare
What are relieving factors for the triple response?
restrict blood supply via pressure, cold water
minimise effect of mast cell degranulation -antihistamine
