Pain And Nociception Flashcards
Which afferents fibres transduce these signals ?
C and a- delta
When tissue is damaged and inflamed it release substances what are they?
Bradykinin, histamine and prostaglandins
Sensitise peripheral nociceptors inducing hyperalgesia
What is fast pain ?
Conducted by a-delta fibres Sharp prickling pain Short duration Occurs rapidly Easily localised Mechanical or thermal nociceptors
What is slow pain?
Conducted by c fibres Dull ache, burning Slow onset Persistent Poorly localised Poly modal nociceptors
What receptors detect heat ?
Trpv1-3, trek-1
What receptors detect chemicals ?
Trpv1, asic, drasic
What receptors detect mechanical changes ?
Mdeg, drasic, trek-1
What receptors detect cold ?
Trpm8
What happens in the zone of lissauer and what effect does it have ?
The afferents enter into dorsal horn and go up/down a few spinal segments in the zone of lissauer
It makes it more difficult to localise the pain
What is the substantia gelatinosa ?
Laminae 1 and 2 where nociceptive afferents project into and synapse
What is referred pain ?
Cross talk between afferents which enter dorsal horn through common route
- visceral pain is perceived as having a cutaneous source
Examples of referred pain?
Oesophagus - chest wall Heart- chest and arm Bladder - perineum Ureter - lower abdomen and back Prostate - lower trunk and legs These pains can be useful for clinicians
What are the 3 ascending pain pathways ?
Lateral spinothalamic
Spinoreticulothalamic
Anterior spinothalamic tract
What happens if you have a unilateral spinal cord injury and what is the effect ?
Sensory loss of touch, pressure, vibration and proprioception on the ipsilateral side
Diminished sensation of pain on the contralateral side
Brown sequard syndrome
This is called dissociated sensory loss
What happens in he Trigeminal system ?
Carries info about pain and temp from face and head
Afferents descend ipsilaterally in spinal trigeminal tract to BRAINSTEM
Synapse with 2nd order neurons in pars caudalia
Decussate onto contralateral side to ascend to thalamus in trigeminothalamic tract
Project to cortex via the ventral posteromedial nucleus
What is phantom pain and why do they think it occurs ?
Pain and touch sensations without input
Usually seen in amputees
May occur due to reorganisation in the virtual body maps in cortex and thalamus
What happens in endogenous analgesia and pain modulation ?
Sensory inputs of pain without a sensation
What are the examples of endogenous ligands of cannabis ?
Anandamide
2-arachidonyl-glycerol
What is the purpose of the cortex, thalamus and limbic system in pain stimuli ?
Cortex- involved in localisation of pain
Thalamus - involved in perception of pain
Limbic system- involved in emotional pain
What are the effects of endogenous opioids?
Presynaptic inhibition
- they decrease transmitter release so reduce pain response
Examples of acute pain …
Skin abrasion Deep tissue injury Superficial burn Labour Important for protection
Examples of chronic pain…
Inflammatory pain, neuropathic pain and neuralgias
What is hyperalgesia ?
When tissue is already damaged or inflamed it is unusually sensitive to pain Can be - reduced threshold for pain - increase intensity of pain stimuli - spontaneous pain
What is the gate theory of pain ?
Theory that if there is increased activity in the a-alpha/ beta fibres then there is less stimulation of the c fibres onto the projection neurons to the brain so reduced pain is felt
