Lecture 8:pain Flashcards
What receptors respond to pain
Specialized nociceptors in peripheral tissues
What are some examples of stimuli that set off nociceptors
Extreme temperature (hot / cold), chemical stimuli, intense mechanical stimuli
True or false: pain neurotransmitters are only released peripherally
Fals,e both centrally and peripherally
What are some examples of pain neurotransmitters
Calcitonin gene-related peptide (CGRP)
• Substance P
• Glutamate
What type of nerve fibers send out ; carry “sharp, fast” pain
Aδ fibers, myelianatated
What type of fibers send out dull, aching pains
C fibers
What type of fibers are normally associated with pain
A delta
C fibers
What are the cutaneous nociceptors
Free nerve enedings
Explain silent nociceptors aciftivation
ONLY activated by pain neurotransmitters &
inflammatory signals
what type of amplification do silent nociceptors do
Temporal and spatial amplification
Why does it feel like Pain can radiate
Since they are activated by other inflammatory signals (other receptors can cause the, to acifgiate and send m pain signals )
What is the ascending nociceprive pathway for the body (trunk and limb)
Anterolateral system (specifically lateral spinothalamic)
Which part of the rhe anterolateral system is part of the nociceprive pathways for body
Lateral spinothalamic tract
Ascending nociceptive pathways for the face is carried by what
Cranial nerve’s CN V, VII, XI, X
What are the two pain pathways
Lateral sensory = discriminative
Medial affective = motivational
Which is the neospinothalamic tract: the medial affective or lateral sensory
Lateral sensory
Which is the paleospinothalamic tract: the medial affective or lateral sensory
Medial affective
The lateral sensory discriminative pathways has projections to where and what does that lead to
Projections to the 1 somatosensort
Helps us locate where specifically the pain is, and help us discriminate
What fibers are used in lateral sensory pathways for pain
A delta
Which paithway encodes pain location, intensity, and quality
Lateral sensory (discriminative)
The lateral sensory discriminative pathways encodes what
pain location, intensity, and quality
Which pathways is the paleo spinothalamic tract
Medial. Affective (motivational)
Where does medial affective project into
Also includes projections to the reticular formation,
midbrain, hypothalamus, etc. (see L7, Slide 11)
What fiber are associated with medial. Affective pathways
C fibers
What does the medial affective motivational pathways encodes what
Encodes “second pain” (i.e., dull throbbing),
emotional & visceral responses to pain, & descending pain modulation
Which pathway Encodes “second pain” (i.e., dull throbbing), emotional & visceral responses to pain, & descending pain modulation
Medial affective motivational
True or false and explain: there is No single “pain center” in the brain à
True
network of areas called the “cortical pain matrix”
Which pain system facilitates pain localization and explain
Lateral
It sends signals to Lateral pain system
1o + 2o somatosensory cortices; somatotopic organization facilitates pain localization
What is the cortical location of lateral pain system
1o + 2o somatosensory cortices;
What is the cortical location of the medial pain system
Includes anterior cingulate cortex, insula, + prefrontal cortexàconnections to amygdala + hypothalamus linked to emotional + visceral responses
Cortical Pain Matrix
Why is the medial pain system associated with the emotional aspect of pain
Includes anterior cingulate cortex, insula, + prefrontal cortexàconnections to amygdala + hypothalamus linked to emotional + visceral responses
Cortical Pain Matrix
What are some examples of endogenous optiods
Enkephalins, endorphins, dynorphins
What do endogenous opinions act on in the pain. System
act on Pain receptors
What does activation of opioid receptors cause
Causes hyperpolarization
of neuronsàless excitability; more difficult to depolarize
Does hyperpolarizafion mean neutrons are more or less excitable
Less excitable (more difficult to depolarize)
How are the ways that activation of opiod receptors
cause hyperpolarization
Inhibition of Ca2+ channels and/or opening of K+ channels
• Opioid receptors in peripheral nerves are upregulated in response to inflammation which increase analgesic effects
• Immune cells release endogenous opioid precursors
What is referred Pain
Tissue injury / other nociceptive stimuli in one area is perceived as pain elsewhere
What is the main theory explained reffered pain
sensory neurons from visceral and somatic (typically cutaneous) tissues converging at
the same spinal level
• Brain interprets pain as coming from the higher output (somatic) areaà“playing the odds”
• Can also refer between two somatic areas
Explain the concept of playing the odds in refered pain
sensory neurons from visceral and somatic (typically cutaneous) tissues converging at the same spinal level (synapse on same population of secondary neutrons
• Brain interprets pain as coming from the higher output (somatic) areaà“playing the odds”
=Moore common to get sensory information (not visceral) therefore brain assumes that’s where the pain is coming m
What is referral pattern for the heart
Thoracic region t1 to t5
Left hand side partially down the arm
What is referral pattern for the diaphragm/lung
C3c4c5
Refers top neck and shoulders
What is referral pattern for the kidneys
T8 to l1
Lower back
What is referral pattern for the tongue and palate
Cranial nn
Head, neck, face
What are the two types of chronic pain
Chronic nociceptive pain
chronic neurogenic pain
What is chronic nociceprive pain
Chronic activation of nociceptors (ex: chronic inflammatory disease)
What is the treatment for chronic nociceptive pain
Requires treatment of underlying inflammation or tissue damage
Chronic activation of nociceptors is associated with what type of chronic pain
Chronic nociceptive pain
Chronic neurogenic pain is rhe result of what
Lesion to somatosensory system
True or false and explain
In chronic neurogenic pain, the pain does not persist after injury heals
False, it does persist
What 2 things characterize neurogenic pain
Hyperalgesia
Allodynia
What is hyperalgesia
There is a real noxious stim that is very low intensity (normal to feel pain) but it is perceived as much more severe than it actually is (disproportionate)
There is a real noxious stim that is very low intensity (normal to feel pain) but it is perceived as much more severe than it actually is (disproportionate)
Is what type of condition
Hyperalgesia
What is allodynia
Painful reaction to a stimuli that should not normally cause pain at all (non noxious stim causes pain)
Painful reaction to a stimuli that should not normally cause pain at all (non noxious stim causes pain)
Is associated with what condition
Allodynia
True or false: chronic neurogenic pain is a summation of low intensity noxious stim
True
Chronic neurogenic pain may lead to what 2 phenomenon
Dysesthesias or parasesthesias
What is dysesthesia
Spontaneous pain (ex: burning)
What is parasesthesia
Odd spontaneous sensation that is not necessarily pain (ex: tingling)
What is the mechsm for neurogenic pain
Maladaptive sensitization
Maladaptive sensitization . Leads to amplification of what
Noxious Stim
where are cell bodies of inhibitory interneurons located
substantia gelatinosa
explain the main concept behind gate control theroy
balacne between nociceptive input and touch input
(trying to shift balance to touch input to reduce pain signalling)
inhibitory interneurons are inhibited by what fibers
a delta and c fibers
inhibitory interneours are activated by what fibers
a beta
where do nociceptive pain fibers (primary neurons) synapse with 2nd neurons
in nucleus proprius and inhibitory interneurons in substantia gelatinosa
be able to explain graphic of gate control theory
true or false: gate control theory is the more localized response
true, it happens within the spinal segment
what structure of the brain is involved in top down modulatory systems (general)
brainstem
what are the 3 main location of the brainstem involved in top down pain modulalation
midbrain (periaqueductal grey)
rostral pons (locus coreolus)
medellu (nucleus raphe magnus)
what is the midbrain structure involved in pain modulation
midbrain (periaqueductal grey)
what is the rostral pons structure involved in pain modulateion
rostral pons (locus coreolus)
what is the medulla structure involved in pain modulation
medellu (nucleus raphe magnus)
what two brainstem structure stimulate the creation of endogenous opioids
locus coreolis
nucleus raphe magus
what brain structure is involved in the noradrenic system
locus coreolus (in the pons)
what brain structure is involved in the seratonergic system
nucleus raphe magus (medullaO
what is the first brain stem structure to receive pain information from cortical and subcortical area of the pain matrixx
midbrain (periaqeductal gary)
what is the way that the brainstem structures modulate pain from a top down method
1) inhibit presynaptic neuron (do not allow the delta and c fibers to synapse with secondary neurons
2) activate inhibitory interneours whose cell bodies are in the substantial gelatinosa
true or false: descending influences are purely inhibitory for pain
false, they have a modulatory role so they can also enhance nociceptions
what are the two types of maladaptive sensitization that can occur
1) peripheral sensitization
=due to changes in free nerve endings (a delta and c fibers)
2) central sensitization
=due to changes in the dorsal root of spinal cord
peripheral sensitization is caused by changes in what
changes in free nerve endings (a delta and c fibers)
central sensitization is caused by changes in what
dorsal horn of spinal cord
what are the physiological reasons behind peripheral sensitization
1) over expression of sodium channels (increases resting membrane potential = easy to depolarize)
2) over expression of capcacin receptors which leads to burning sensation
what are the physiological reasons behind central sensitization
1) over expression of glutamate receptors in secondary sensory neurons (increased excitability)
2) over expression of sodium, under expression of potassium
=leads to higher resting membrane potential, easy to depolarize
3) decrease in inhibitory neurotransmitters (disinhibition)
what pain treatment acts on peripheral nocicepots
anti steroidal immune drugs or topical anaesthetics
anti steroidal immune drugs or topical anaesthetics act on what
peripheral nocicepts
what pain treatment acts on brainstem nuclei
opioids or antidepressants (serotonin or norepinephrine uptake inhibitors)
opioids or antidepressants (serotonin or norepinephrine uptake inhibitors) act on what
brainstem nuclei
what pain treatment acts on the emotional/psychological aspect of pain
coping strategies, cogniticate behavioural therapy, relaxtion
coping strategies, cogniticate behavioural therapy, relaxtion acts on what
psychological process of pain
what pain treatment acts on posterior horn
options and NMDA antagonists
options and NMDA antagonists act on what
posterior horn
