pain Flashcards
define pain
the feeling or perception of irritating, sore, stinging, aching, throbbing, miserable, or unbearable sensations arising from a part of the body.
define noiception
is the sensory process that provides the signals that trigger pain
where abouts are noiceptors found
the periphery as simple free nerve endings.
Tissue damage and inflammation triggers release of which substances.
prostaglandins, bradykinin and histamine.
do nocioceptors have myelin
No myelin, terminates naked.
what is the function of prostaglandins, bradykinin and histamine
sensitise peripheral nocioceptors and induce hyperalgesia.
what happens when nocioceptors are sensitised due to inflammatory mediators, where do they send signals
spinal cord
blood vessels- to mast cells in order to enhance inflammation.
what is the neurotransmitter that causes mast cells to release histamine
substance P
what inflammatory mediator triggers chemonoiceptors
bradkyinin
what 2 types of fibres transduce the stimulated noicoceptive fibres
unmyelinated C fibres and thinly myelinated Ad fibres.
what are the 3 modalities of noicoception
mechanical
chemical thermal
what type of receptor increases the number of action potential with increased amount of heat.
noiceptors- tells you how hot something is
thermoreceptor- just tells you if something is hot.
large diameter and slow condition are which receptors
pain and temperature
small diameter and fast conduction are which receptors
proprioception and discriminative touch.
what type of fibres carry the first pain associated with injury
Fat Ad fibres
what are the characteristics of the first pain associated with injury
Sharp or prickling Easily localised Occurs rapidly Short duration Mechanical or thermal nociceptors
what type of fibre carry the second pain associated with injury
C fibres
what are the characteristics of the second pain associated with injury
dull ache, burning poorly localised slow onset persistent polymodal noiceptors.
where are the cell bodies of noicoceptors
dorsal root ganglion
how is the signal transducer from the dorsal route horn.
Nociceptive fibres have their cell bodies within the dorsal root ganglion.
Afferent terminals enter the dorsal horn and travel up/down a short distance within the Zone of Lissauer.
Afferent terminals synapse onto neurones within the superficial laminae of the dorsal horn.
Principle areas innervated by nociceptor afferents are lamina I and lamina II (substantia gelatinosa).
Nocicecptive fibres – first order neurons
in which laminae of the DRG do nocioceptors synapse
first and second.
what is the zone of lissauer
where afferents travel up a few segments in the spinal cord before synapsing
how does referred pain occur
cross talk- viscera and the skin enter spinal cord through common routes and target overlapping populations of spinal neurons.
so internal stimuli can cause referred pain at the affected dermatome level in the body.
where is angina pain referred
upper chest wall and left arm
where is appendicitis referred
abdominal wall
where is ureteric pain referred
lower abdomen
is the spinothalamic pathway contra/ipsilateral
contralateral- crosses at the level of entry.
what is the function of the ascending pathways
• Processes afferent inputs from peripheral mechano-, thermal and polymodal nociceptors.
what are the 3 components of the ascending pathways
lateral-spinothalamic tract
spinoreticulothalamic tract (paleospinothalamic)
anterio-spnothalamic
what pathway carries pain and temperature
spinothalamic
what pathway carries proprioception and 2 point touch
dorsal column pathway
A unilateral lesion in the spinal cord will produce what effect
produce sensory loss of touch, pressure, vibration and proprioception on same side below level of lesion and pain an temperature loss on opposite side of the lesion.
what type of sensory information does the trigemionathamic tract carry
sensory information from the face and head.
what is the name of the structure where the primary and secondary neurone of the trigeminothalamic tract synapses
pars caudalis.
where do dorsal column and spinothalamc tract project in the thalamus
VPL
where does the trigeminothalamic tract project in the thalamus
VPM
is the trigeminothalamic tract contralateral or ipsilateral
contralateral
define phantom pain
Pain and touch sensations with no sensory inputs
what is the most likely cause of phantom pain
cortical re-organization in the ‘virtual’ body maps of thalamus and cortex, e.g. foot taken over by leg.
do we have endogenous opiates
yes
what is the function of opioids
relieve pain by acting pre and post synaptically.
give 2 examples of endocannabinoids
anadamide and 2-arachidonyly-glycerol
what receptors do anadamide and 2-arachidonyly-glycerol work on
CB1, and CB2
what is the function of endogenous ligands
Inhibits behavioural responses to acute noxious stimuli, limits hyperalgesia and neuropathic pain.
define hyperalgesia
A reduced threshold for pain
An increased intensity of painful stimuli
Spontaneous pain.
are interneureones stimulatory or inhibitory
inhibitory
how can you control your own pain.
Descending ‘endogenous analgesic’ pathways from periaqueductal grey and reticular formation decrease transmitter release from primary afferent terminals by an interaction with opioid receptors.
Binding of opiates, decreases neurotransmitter release, and decreases AP up spinothalmic pathway, so you can control your own pain.
define innocuous stimulus
not harmful
what afferents carry painful stimuli
c-afferents
what afferents carry non painful stimuli
AB-afferents
