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Neuro Test 2
2/5 Pain
66
Dentistry
Graduate
02/09/2014

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Cards

Term
Pain…

Is one modality of __________
Is the ________ of unpleasant or aversive stimulation (sensory and emotional experience)
Warns of _______ (physiological relevance)
Definition
Is one modality of somatosensation
Is the perception of unpleasant or aversive stimulation (sensory and emotional experience)
Warns of injury (physiological relevance)
Term
True or false

Pain is highly individual and subjective
Definition
True
Term
What pathways carries pain information?
Definition
spinothalamic
Term
The spinothalamic tract is part of what ascending sensory system?
Definition
anterolateral system
Term
Small DRG unmyelinated axons that enter the cord for pain and temperature are ____ fibers.
Definition
C fibers
Term
small DRG unmyelinated axons (C fibers) enter the cord and synapse in _____________, the cross in the ___________ and ascend in the __________ tract.
Definition
synapse in substantia gelatinosa (lamina II), then cross in the Ventral White Commissure and ascend in the Anterolateral Tract.
Term
Under normal conditions, C fibers release what neurotransmitter to activate AMPA receptors?
Definition
Glutamate (tiny vesicles)
Term
If there is a high frequency of action potentials (high intracellular Ca+), what neurotransmitter will C fibers release?
Definition
Substance P (denser vesicles)
Term
Where do primary afferent C fibers synapse
Definition
on dendrite within substantial gelatinosa (layer II)
Term
What neurotransmitter enhances and prolongs the action of glutamate acting on AMPA receptors?
Definition
substance P
Term
Are delta fibers myelinated?

Are they smaller or bigger than C fibers?

Do they transmit slower or faster than C fibers?
Definition
myelinated

bigger

transmit faster
Term
Which lamina do delta fibers synapse?

Which lamina do C fibers synapse
Definition
I (marginal layer of dorsal horn)

II (substantia gelantinosa of dorsal horn)
Term
What fibers are for proprioception?

Where do they synapse?
Definition
beta fibers

lamina V and ventral horn (important for reflexes)
Term
What type of information is conducted the fastest?
Definition
proprioception (evolutionary advantage of running away)
Term
What fibers are the fastest- bigger and myelinated?
Definition
alpha and beta
Term
What fibers are small but myelinated?
Definition
delta
Term
What fibers are unmyelinated and small, slow.
Definition
c fibers
Term
What fibers are involved with sharp pain?

What fibers are involved with dull pain?
Definition
delta

c fibers
Term
What are the free nerve endings of primary sensory DRG and trigeminal ganglia neurons (a few wrap arounds of schwann cells, no connective tissue, just free branches)
Definition
nociceptors
Term
What activates nociceptors?
Definition
harmful stimuli
Term
Membran contains "____________" receptors
Definition
sensory detection (non-selective cationic channels, Na+, Ca2+)
Term
What receptor detects noxious heat (>53 degrees C)?
Definition
TRPV2 (transient receptor potentials vanilloid 2)
Term
What receptor detects capsaicin (chili)/ vanillin (~43 degrees C)?
Definition
TRPV1
Term
What receptor detects warmth (~27-39 degrees C)?
Definition
TRPV3, TRPV4
Term
What receptor detects menthol/icilin (cool ~20 degrees C)?
Definition
TRPM8
Term
What receptor detects noxious cold (<5 degrees C)/garlic/wasabi?
Definition
TRPA1
Term
What are the classes of nociceptors that are all located in skin and deep tissues?
Definition
Thermal - extreme temperatures – A-delta fibers
Mechanical - intense pressure – A-delta fibers - sharp pain
Polymodal - both intense mechanical, chemical or thermal stimuli – C fibers (unmyelinated) – dull burning
Term
True or false:

Pain sensation and pressure sensation have the same axons.
Definition
False

pain sensation is not the same as pressure sensation like the corpuscles. You can press harder, but it's more like touch, and it doesn't fire any faster based on pressure. It’s not encoding pain just because you press harder. Pain is mediated through a completely different set of axons
Term
When cells are damaged (endothelial/platelets), it releases chemicals that activate and sensitize (hyperalgesia-cause increase pain) at the ___________.
Definition
free nerve endings
Term
After chemicals stimulate nerve endings during an injury, they are depolarized and fire AP to excite the __________ neuron in the dorsal horn.

These mediators released at the site of injury causes _______/________.
Definition
dorsal ganglion

vasodilation/extravasation (neurogenic inflammation)
Term
How does aspirin work to reduce inflammation?
Definition
inhibits arachidonic acid cyclooxygenase
Term
Thermal nociceptors are members of the ________ gene family.

Are they (selective or non-selective) cation channels?
Definition
transient receptor potential (TRP)

non-selective - Na, Ca
Term
True or false:

Thermal nociceptors are activated at all temperatures
Definition
False

Activated by extreme temp:
< 5 C or > 45 C
Term
True or false:

Thermal nociceptors are excitatory.
Definition
True

depolarizing (permeable to Na, K, and Ca)
Term
When pressing a blunt instrument on your finger, you will record __________ fibers.

When pressing a sharp instrument on your finger, you will record _________ fibers.
Definition
mechanosensory (pressure)

nerve ending (mechanical nociceptor)
Term
Will pressing a sharp instrument on your finger report Pacinian and Ruffini corpuscles?
Definition
No Pressure is NOT the same as pain
Term
What is the term for when a stimulus that was not considered painful immediately after injury becomes perceived as painful (Repeated noxious leads to recruitment of previously unresponsive neighboring nociceptors)?
Definition
hyperalgesia (sensitization)
Term
What type of reflex is involved with sensitization of nociceptors?
Definition
axon reflex (1 cell reflex) - no synapse between sensory arm and motor arm of the reflex
Term
After tissue damage, the sensation to pain to subsequent stimuli is (increased or decreased) at primary and secondary (surrounding) sites of injury?
Definition
increased
Term
What is the term called when pain thresholds decrease or magnitude of pain from suprathreshold stimuli increases?
Definition
hyperalgesia
Term
What is the painful response to otherwise innocuous mechanical stimulus (ex: sunburn)
Definition
allodynia
Term
With severe persistent injury, ___ fibers fire repetitively or "wind up" resulting in increased ______ release in the spinal cord that activates _______ receptors.
Definition
With severe persistent injury, C fibers fire repetitively or “wind up” resulting in increased glutamate release in spinal cord that activates NMDA receptors (permeates calcium)
Term
When the C fibers fire repetitively resulting increased glutamate release, which activates NMDA receptors, what happens that causes up regulation of transmitters and receptors?

What type of sensitization is this?
Definition
synaptic plasticity

central sensitization (ex: phantom limb pain)
Term
What tract does the pain sensation follow?
Definition
spinothalamic
Term
Is the spinothalamic tract, in the white or gray matter in the spinal cord?

Where does it go in the thalamus?

Where does it go in the cortex?
Definition
Antero-lateral white mater

central-lateral nucleus and ventral-posterior-lateral nucleus

postcentral gyrus (pain goes to same places as mechanosensory homunculus)
Term
Identify whether it is VPL/VPM (neospinothalamic) or Intralaminar complex (paleospinalthalamic) pain pathway through thalamus:

-receive nociceptive specific and other sensory inputs
-spinothalamic tract (STT & TTT)
-Includes projections from the spinoreticulothalamic tract
-project to primary somatosensory cortex
-diffuse cortical projections
-neurons have small receptive fields - injury location
Definition
-receive nociceptive specific and other sensory inputs (neospinothalamic)
-spinothalamic tract (STT & TTT) (neospinothalamic)
-Includes projections from the spinoreticulothalamic tract (paleospinalthalamic)
-project to primary somatosensory cortex (neo)
-diffuse cortical projections (paleo)
-neurons have small receptive fields - injury location (neo)
Term
What ascending pathway is responsible for arousal when there is pain?

Where does this tract go?
Definition
spinoreticular tract

to reticular formation of pons / medulla (level of attention); and onto thalamus
Term
What ascending pathway is responsible for emotion and memory integration of pain?

Where does this tract go?
Definition
Spinomesencephalic tract

to mesencephalic reticulum, lateral periqaueductal grey in midbrain; and on to hypothalamus and limbic system (emotion and memory integration)
Term
Where does the spinoreticular tract receive collaterals?

Where does it synapse?
Definition
medulla

pons
Term
Where does the spinomesencephalic tract synapse?

Is it in ascending or descending control?
Definition
(periaqueductal gray matter) in the mid brain

descending control
Term
(ascending or descending) pathways can regulate relay of nociceptive information in the spinal cord.
Definition
descending
Term
If you stimulate the ________ area of the brain, you can modulate the sensation of pain.

However, what are the other parts that you can stimulate noradrenaling and serotonin to slow the integration of AP from the primary afferent to synapse in the dorsal horn?
Definition
PAG (periaqueductal gray mater)

locus ceruleus and nucleus raphe
Term
How does morphine work as an analgesic?
Definition
activates receptors on locus ceruleus to control the level of excitation where information comes in (doesn't make you numb like sodium channel blocker in primary afferent that prevents transmission of the AP)
Term
Where are the 2 places where external and endogenous opioids work?
Definition
pre-synaptic sensory neuron (smaller AP)
post-synaptic sensory neuron (smaller EPSP)
Term
Determine if the opioid is working on the presynaptic or postsynaptic neuron:

Opening K+ channel hyper polarizes terminal so action potential is smaller (thus less glutamate and substance P --> less pain formation coming into dorsal horn)
Definition
presynaptic
Term
Determine if the opioid is working on the presynaptic or postsynaptic neuron:

Opening K+ channel hyperpolarizes cell and causes inhibitory conductance and shunting which makes the EPSP smaller.
Definition
postsynaptic
Term
True or False:

You can make yourself feel or not feel pain.
Definition
True

Placebo effect- your own convictions can trigger areas in the brain (raphe, locus coeruleus, PAG) to release endogenous opioids, endorphins, and modulate pain
Term
What fibers can stimulate the local inhibition C fiber cause a reduced or weak activation of the postsynaptic neuron sending up the sensory pathway?
Definition
beta fibers (proprioception)/intrafusal fibers - why we rub skin or shake when something is painful
Term
VPL / VPM project to ______________ cortex and then to secondary somatosensory cortex for awareness, location and “intensity” of pain
Definition
primary somatosensory
Term
Medial thalamus projects to anterior ______ cortex for autonomic / visceral component of pain
Definition
insular
Term
Intralaminar nuclei of medial thalamus projects to ______ _______ cortex (limbic association cortex) for emotional component of pain (circuit of Papez)
Definition
anterior cingulate
Term
What type of pain is it when visceral pain maps out in nearby regions of the skin?
Definition
referred pain
Term
What nociceptors are normal not active but firing threshold reduced by various insults.
Definition
silent nociceptors
Term
What is released by nociceptors which causes mast cells to release histamine, which in turn stimulates the nociceptors?
Definition
substance P
Term
In referred pain, there is a convergence of somatic and visceral afferents on lamina ___.
Definition
V
Term
Which is the one we haven’t talked about related to pain?
1. dorsal horn
2. STT
3. PAG
4. Raphe
5. Locus coeruleus
6. Substantia nigra
Definition
substantia nigra
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