A&P Test 3 Flashcards
Which pathway is the pain pathway?
the anterolateral spinothalamic pathway
What are the three paths that information can take in the corticospinal pathways?
- Decending motor-internal capule- brainstem in medulla:crossover-decend in laterocortical corticopinal tract. 80%
- anterior corticopspinal tract. Crossover in the spinal cord 17%
- doesn’t cros over at all 3%
Fast pain is transmitted through which fibers?
A delta- heavily myelinated
nociceptors are the same thing as
free nerve endings
Fast pain gets routed through which portion of the anterolateral tract?
lateral
which neurotransmitter is used for fast pain?
glutamate
where does fast pain information get sent to in the brain?
Parietal lobe
Fast pain fibers are parallel to which fibers?
DCML
Which part of the parietal lobe takes care of the lower extremities?
top portion
Which part of the parietal lobe post central gyrus takes care of the trunk?
second to the top
Which part of the parietal lobe post central gyrus takes care of the upper extremities?
the second from the bottom
Which part of the parietal lobe post central gyrus takes care of the face?
the bottom portion
why are we able to localize fast pain?
because fast pain is routed to the same areas that DCML signals are sent
Where does cross over happen for fast pain?
in the anterior white commisur
What does neo mean?
new
what is another name for the fast pain tract besides spinothalamic?
neospinothalamic
what is another name for the slow pain tract?
paleospinothalamic
why is the fast pain called the neospinothalamic tract?
it is a new pathway that has branched off the slow pathway recently, making it more sophisticated.
what does Smidt think of with the word paleo?
dinosaurs
Slow pain uses what kind of fibers?
C fibers nonmyelinated
what type of neurotransmitters are used in slow pain?
- substance P(main one)
- CGRP(calcitonin gene related peptide)
- Glutamate (works slower here)
What makes the slow pain pathway slow?
c fibers
the slow release, binding and effect of neurotransmitters
a lot of slow pain pathways terminate at the
top of the brainstem
Why does slow pain have poor localization?
because the information doesn’t make it all the way up to the parietal lobe where information like this is sorted
Thermoreceptors and vibration sensors are associated with which pain pathway?
slow pain pathway
Where does slow pain have synapses in the spinal cord?
substantia gelatinosa
lamina 5
After lamina 5, slow pain crosses over at the _____ and goes into the _______ part of the anterolateral pathway
anterior white commisur
anterior
If you have fire on your finger, what is the pathway the pain will take
dorsal rootlets
synapses in the dorsal gray horn
cross over in the spinal cord
-slow: ascends in the anterior anterolateral pathway
-fast: ascends in the lateral anterolateral pathway
slow pain engages what part of the brain that fast pain doesn’t?
emotional. It messes with your head
Where are the emotional centers of the brain found?
very close to the middle of the brain
where the brainstem connects with the diencephalon
What is the ventrobasal complex?
a place where the dcml pathway runs through
what is the reticular formation?
a swath of tissue that is located in the top of the brainstem where a lot of the slow pain signals terminate
What is the vestibulospinal extrapyramidal tract?
a descending motor pathway.
eye fixation and muscle orientation during acceleration i.e. balance
Olivospinal tracts are what type of tract?
extrapyramidal tract
The reticulospinal tract maintains
baseline muscle tone
the rubrospinal tract is very similar to the tracts that the cerebellum uses and is in charge of
modulating voluntary movement
What are the extrapyramidal tract descending motor pathways?
vestibulospinal
olivospinal
reticulospinal
rubrospinal
What is the descending pain suppression system?
inhibitory in nature and activated by pain.
It is something that operates in the background and helps the body deal with pain
What does DIC stand for?
descending inhibitory complex
The DIC has how many neurons?
3
Where is the primary or initial neuron found in the dic tract?
periventricular nucleus or periaqueductal gray
Where is the periaqueductal gray found?
in the midbrain of the brainstem
Where is the periventricular nuclei found?
right in front of the third ventricle
When the first neuron is excited in the DIC pathway, what does it release, and where?
Enkephalin in the pons
What is situated right in the middle of the pons?
the cell body of our second-order descending neuron
In the pons are enkephalins excitatory or inhibitory?
excitatory
What does the second neuron in our DIC pathway release?
Serotonin
What is the abbreviation for serotonin?
5-HT
Where does serotonin get released by the second neuron in the DIC pathway?
in the spinal cord at the area of the dorsal horn
What does serotonin act on in the DIC pathway?
the third neuron
Is the third order neuron in the DIC pathway big or small?
very small
What does the third order neuron in the DIC pathway secrete?
enkephalin
In the spinal cord are enkephalins excitatory or inhibitory?
inhibitory
What kind of receptors are found on nociceptors in the spinal cord?
enkephalin receptors -these are our pain sensing neurons
Our pain sensing neurons have dendrites where?
in the periphery
What happens when enkephalin binds to our nociceptors in the spinal cord?
it shuts down activity in the pain sensor
After the second neuron in the DIC pathway, where is enkephalin receptors found?
in the next neuron in the ascending pain pathway. There are synapses on lamina 1,2,3 or 5 and from there the transmission would hop over to the other side of the cord and then ascend in the anterolateral pathway.
There are synapses in lamina 1,2 or 3 and from there the transmission in the pain pathway would
would hop over to the other side of the cord and then ascend in the anterolateral pathway.
What is enkephalin?
an endogenous morphine analogue
all of our morphine receptors are actually
enkephalin receptors
What is the specific place in the middle of the pons where we have this first synapse in the Descending inhibitory complex?
raphe magnus nucleus
RMN
If we were to implant electrodes and stimulate either the periventricular nucleus or the periaqueductal gray area, we would expect
an inhibitory pain signal that can reduce the amount of pain that we perceive
What is deep brain stimulation?
activation of the descending inhibitory complex by placing electrodes in either the periventricular nucleus or the periaqueductal gray area
What is something that people rarely hear about but gives us a target for our drugs?
the descending inhibitory complex
A nociceptor out in the periphery senses pain and sends that information to
the spinal nerve
dorsal root
dorsal rootlet
eventually it gets to the first order neuron
this synapses in lamina i, ii, iii or V with the second order neuron
the second ascending pain transmission neuron hops over to the other side of the cord via the AWC
and then rides in the anterolateral columns
slow pain Terminates in the brainstem
fast pain goes through the thalamus to the parietal lobe
The descending pathway first order neuron starts at either the periaqueductal gray or the peri ventricular nuclei and then synapses at the _____ and then
in the middle of the pons (Raphe Magnus Nucleus)
the second neuron travels to the level of the cord it needs to interact with
this releases serotonin
which excites the third order neuron
which releases enkephalin
which binds to both the nociceptor and second order neuron
which is inhibitory and suppresses pain in the pre and post synaptic synapse
You could lift a car off a kid, or completely deaden your pain senses if you have
enough training, self control, and high pain tolerance
the synapse for the second, serotonergic DCIM neuron is found
outside of the gray matter
if we can get a needle close enough to the ________ receptors, you can shut down pain
enkephalin
In reverse adaptation what is happening to our ascending and descending pain pathways, specifically in chronic pain?
Enkephalin does not work as well because there’s less of those receptors and more glutamate receptors
What can elicit a response in a nociceptor?
physical damage
crush injuries
cuts
potassium
Histamines
acids H+ lactic acid
Bradykinin
5-HT/serotonin
ACh
prostaglandings
potassium follows
protons
What type of patients have higher potassium and lower pH?
a patient with diabetes and renal failure that hasn’t had dialysis in a while
Prostaglandins can’t produce pain in itself but they
augment the pain sensation for other things
If we could somehow increase the bioavailability of serotonin near the second order serotonergic neuron, we could potentially
decrease chronic pain
What are things that increase bioavailability of serotonin in the cord?
- SSRI
-paxel
-prozac
*tricyclic antidepressants
Serotonergic neurons like to reuse their serotonin and do this by
a serotonin reuptake system
SSRI’s block the
reuptake system of serotonin
What is an older drug class that is prescribed fairly often for the treatment of chronic pain? Why?
Tricyclic antidepressants
They have other side effects that is sometimes helpful, like drowsiness.
how long have tricyclic antidepressants been around for?
50-60 years
Why did tricyclic antidepressants go out of favor for a while?
their side effects
Because the pressure or DCML sensors run parallel to nociceptors, they can
talk to each other- though it isn’t understood how, it’s probably through some neurotransmitter and receptor.
neighboring neurons can shut down
their neighbor
If you injure yourself, and then you squeeze the part of the body that hurts, you can decrease the pain. what is this called?
lateral inhibition
how does acupuncture work?
lateral inhibition
Where does lateral inhibition work?
in the dorsal horn of the cord
how much dcml pressure sensor information make it out of the dorsal horn if it didn’t go up towards the brain?
not very much. Lateral inhibition stops most of it in the dorsal horn of the cord
what is our primary neurotransmitter for the pain system?
glutamate
Is glutamate ever inhibitory?
no, it’s excitatory
What is drawn in the first order neurotransmitter (the nociceptor that is out in the periphery detecting pain) at the synapse in the dorsal horn between it and the second order neuron that would hop to the other side of the cord and then send information into the anterolateral column and ascend towards the brain?
VG Ca++ channel that opens in response to an AP and allows calcium into the cell
which drives the VP holding glutamate to exocytosis
after glutamate is released into the synapse between first and second order neuron, what does it do?
binds to either AMPA or NMDA receptors
What is an AMPA receptor?
a ligand gated receptor next to an ion channel that opens in response to glutamate and lets Na+ into the cell
What is the primary receptor on the second order neuron in the dorsal horn after the nociceptor?
AMPA
What is the secondary receptor on the second order neuron in the dorsal horn after the nociceptor?
NMDA receptor
What is a NMDA receptor?
a slow ligand gated receptor next to an ion channel that opens in response to glutamate and lets a lot of Ca+ and a little Na+ into the cell
Why are NMDA’s slow?
because Mg++ blocks the opening intracellularly and the receptor has to wait for the AMPA receptor to produce an EPP to depolarize the inside of the cell and repel Mg++ from the NMDA’s opening
If we depolarization via an AMPA receptor, and want to send more or a second type of information using the same synapse, what do we use?
NMDA receptor
The more NMDA receptors that we have, the
more information that we can send
NMDA receptors are placed in our CNS as a result of
development
What is the tertiary receptor on the second order neuron in the dorsal horn after the nociceptor?
Kainate
What blocks the NMDA receptors?
Ketamine
Lead
Ethanol
Nitrous
Tramadol
People who are wasted don’t feel much pain, why?
their NMDA receptors are blocked
If we live in an old house and eat paint chips, it will
block our NMDA receptors
Ketamine is what kind of drug?
a dissociative. It shuts off part of the CNS but doesn’t put people to sleep
Ketamine effects the _______ of pain
perception
Ketamine ONLY works on which receptors?
NMDA. You can still have some pain through the AMPA and other receptors
Tramadol is a terrible drug, why?
tramadol doesn’t do a ton with enkephalin receptors (morphine receptors)
What does tramadol do to help with pain?
Serotonin reuptake inhibitor
inhibits NMDA but not AMPA
Who is a good candidate for tramadol?
elderly
people super sensitive to opiates.
Tramadol should not be used as a pain med after
surgery
What do Kainate receptors mediate?
GABA activity in the brain
Chronic pain inserts more ______ receptors
AMPA and NDMA
What are the ionotropic glutamate receptors?
Kainate
AMPA
NDMA
These mediate changes to the cell wall permeability to ions
What is the second, broad category of glutamate receptors?
metabotropic
GPCR’s that are involved in signal transduction
What is the first class of glutamate receptors?
ionotropic
If you remove the source of pain, do the excess NMDA receptors go away?
Yes, but it will take a long time, like months
Where does ketamine work in kids that makes it useful?
in the brain
