Ascending Tracts | Pain Modulation: Gate Control Theory
Summary
TLDRThis educational video script delves into the complex mechanisms of pain modulation, emphasizing the importance of the gate control theory and the descending analgesic system. It explains how endogenous chemicals like GABA, endorphins, and dynorphins work to inhibit pain at the spinal cord level. The script also highlights the role of higher brain structures in modulating pain perception, providing insights into our body's innate pain management system.
Takeaways
- 🧠 Pain modulation is crucial and involves endogenous systems within the body that help inhibit pain.
- 🔄 There are two primary types of pain modulation: the Gate Control Theory and the Descending Analgesic System.
- 🚪 Gate Control Theory suggests that non-painful touch receptors can 'close the gate' on pain signals, reducing the perception of pain.
- 🌟 The Gate Control Theory involves the activation of inhibitory neurons that release chemicals like GABA to decrease pain signals in the spinal cord.
- 🛑 The Descending Analgesic System involves higher brain structures that send signals down to the spinal cord to modulate pain.
- 💊 Descending pathways can release endogenous opioids, such as enkephalins and dynorphins, which are similar to morphine and help reduce pain.
- 🌐 The periaqueductal gray matter (PAG) and periventricular gray matter are key regions in the brain that regulate the Descending Analgesic System.
- 🔻 The locus coeruleus, rich in norepinephrine, and the raphe nuclei, rich in serotonin, are involved in the Descending Analgesic System and influence pain modulation.
- ⚡️ The release of neurotransmitters like substance P and glutamate at synapses in the spinal cord determines the speed and intensity of pain signals.
- 🔄 The spinothalamic tract is a key pathway for pain and temperature signals, with C fibers primarily responsible for slow pain and A-delta fibers for fast pain.
- 📡 Higher brain structures, such as the limbic system, sensory cortex, and insular cortex, can influence the PAG and pain modulation through descending pathways.
Q & A
What is the main topic discussed in the video?
-The main topic discussed in the video is the modulation of pain, specifically the endogenous analgesic systems that regulate pain within our bodies.
What are the two types of pain modulation mentioned in the video?
-The two types of pain modulation mentioned are the gate control theory and the descending analgesic system.
What is the gate control theory and how does it work?
-The gate control theory is a mechanism that modulates pain at the spinal cord level. It works by activating touch receptors when we rub an injured area, which in turn stimulate inhibitory neurons that release chemicals like GABA to inhibit pain signals.
What are the roles of A-delta and C fibers in pain transmission?
-A-delta fibers are responsible for transmitting fast pain signals, releasing the neurotransmitter glutamate at the synapse. C fibers transmit slow pain signals and are believed to release substance P at the synapse, which is slower and can also decrease the threshold for pain.
What is the role of the substantia gelatinosa of Rolando in pain modulation?
-The substantia gelatinosa of Rolando is a structure in the Rex lamina of the spinal cord that plays a crucial role in pain modulation. It is where C fibers synapse and is involved in the gate control theory by being influenced by inhibitory neurons stimulated by touch receptors.
What are the main structures involved in the descending analgesic system?
-The main structures involved in the descending analgesic system include the periaqueductal gray matter, periventricular gray matter, locus coeruleus, reticular formation, and the raphe nucleus magnus.
Which neurotransmitters are associated with the descending analgesic system and their respective structures?
-The locus coeruleus is associated with norepinephrine, while the reticular formation (para giganto cellular reticular nuclei) and the raphe nucleus magnus are associated with serotonin (5-hydroxytryptamine).
How do the descending analgesic pathways reduce pain perception?
-The descending analgesic pathways reduce pain perception by releasing chemicals such as norepinephrine and serotonin onto inhibitory neurons, which in turn release endogenous opioids like enkephalins and dynorphins that inhibit the substantia gelatinosa from sending pain signals up the spinal cord.
How do higher brain structures influence the descending analgesic system?
-Higher brain structures such as the limbic nuclei, sensory cortex, insular cortex, hypothalamus, and cingulate gyrus can influence the descending analgesic system by sending signals to the periaqueductal and periventricular gray matter, indicating when to activate the descending pathways.
What are the endogenous opioids released by the descending analgesic system and their function?
-The endogenous opioids released by the descending analgesic system include enkephalins and dynorphins. These natural opioids function similarly to morphine, inhibiting pain signals at the spinal cord level.
Outlines
🧠 Pain Modulation and Endogenous Systems
This paragraph introduces the concept of pain modulation, emphasizing its importance alongside the pain pathway itself. It mentions the anterior lateral system and the spinothalamic tract, hinting at a recap without deep dive. The focus is on two types of endogenous pain modulation systems that the body uses to inhibit pain: the gate control theory and the descending analgesic system. The gate control theory is introduced with a scenario of bumping one's head to illustrate how rubbing the area can alleviate pain by activating different touch receptors.
🔬 Neurotransmitters in Pain Pathways
The second paragraph delves into the role of neurotransmitters in pain pathways, specifically substance P for slow pain and glutamate for fast pain. It explains how C fibers and A-delta fibers activate different second-order neurons and the synapse points involved. The paragraph also touches on the chemical factors released due to stimuli like histamine, protons, and potassium, and how substance P can decrease the pain threshold through an axon reflex.
🚪 Gate Control Theory Mechanism
This paragraph explains the gate control theory in detail, describing how touch receptors activated by rubbing an injured area can stimulate inhibitory neurons. These neurons release gamma-aminobutyric acid (GABA), which inhibits the transmission of pain signals at the spinal cord level. The summary highlights the process of how action potentials from touch receptors can inhibit the pain pathway, reducing the severity of pain perception.
🌱 Descending Analgesic System and Neuroanatomy
The fourth paragraph discusses the descending analgesic system, which involves various brain structures such as the periaqueductal gray matter, periventricular gray matter, locus coeruleus, reticular formation, and raphe nucleus magnus. It explains how these structures are involved in sending descending fibers to modulate pain at the spinal cord level, focusing on the release of neurotransmitters like norepinephrine and serotonin.
💊 Endogenous Opioids and Pain Inhibition
The final paragraph explains how the descending analgesic system releases chemicals similar to morphine, specifically endorphins and dynorphins, which are natural opioids produced by the body to reduce pain. It discusses how these chemicals inhibit the substantia gelatinosa of Rolando from sending action potentials, thereby decreasing pain perception. The paragraph also explores how the brain structures involved in the descending pathway are stimulated by the anterolateral system, sensory cortex, and limbic nuclei.
Mindmap
Keywords
💡Pain Modulation
💡Gate Control Theory
💡Descending Analgesic System
💡Substance P
💡Glutamate
💡GABA
💡Periaqueductal Gray Matter (PAG)
💡Endorphins
💡Dorsal Column Medial Lemniscus Pathway
💡Locus Coeruleus
💡Raphe Nucleus Magnus
Highlights
Introduction to pain modulation as a critical aspect of the pain pathway.
Discussion on endogenous analgesic systems that inhibit pain through chemicals produced within the body.
Introduction of two types of pain modulation: gate control theory and the descending analgesic system.
Explanation of the gate control theory and its role in pain alleviation through touch receptor activation.
Mechanism of rubbing an injured area to reduce pain by activating different touch receptors.
Description of the substantia gelatinosa of Rolando and its importance in pain modulation.
Role of C fibers and A-delta fibers in pain transmission and the release of substance P and glutamate.
The effect of substance P in lowering the threshold for pain activation through axon reflex.
How the activation of touch receptors can inhibit pain signals through the release of GABA.
Overview of the descending analgesic system and its various neural structures.
Function of periaqueductal gray matter, periventricular gray matter, and locus coeruleus in pain modulation.
Importance of neurotransmitters norepinephrine and serotonin in the descending analgesic pathway.
The release of endogenous opioids like enkephalins and dynorphins for natural pain relief.
How the brain uses sensory input to modulate pain through the descending analgesic system.
Influence of higher brain structures like the limbic system and cerebral cortex on pain modulation.
Practical applications of understanding pain modulation for pain management and treatment.
Conclusion summarizing the importance of pain modulation mechanisms in the nervous system.
Transcripts
all right engineers in this video we're
gonna talk about the modulation of pain
it's equally as important as the pain
pathway itself if you guys haven't
already seen it please go watch the
video on the spinothalamic tract where
we talk about the anterior lateral
system well dip into a little bit again
in this video but we're not gonna do
into super depth alright
so pain modulation is super super
important we're gonna talk about two
different types of pain modulation and
they're all endogenous and meaning that
we all do it on our own inside of our
body we make the chemicals that are
necessary to be able to inhibit pain so
what are these two analgesic systems so
the two analgesic systems are the pain
modulating systems is actually going to
be regulate at two different levels so
there's pain modulating modulation what
are these two different pain modulations
okay one that we're going to talk about
first is the gate control theory and the
next one we're gonna talk about is the
descending analgesic system okay so
we're gonna talk about these two now
this gate control theory what's really
really important all right let's take a
scenario let's say I bumped my head
against something sharp or something
should hard and I hit it really hard and
it hurts right it induces pain because
of activating the a delts are activating
the C fibers right and it says that
information up to my cerebral cortex
helps you become aware of it and where
that pain is but there's a way that we
can kind of lessen the pain if any of
you I know that some of you guys have
definitely done this if you hit your
elbow against something or hit your head
against something what do you do
you rub it ah what why because it helps
to kind of alleviate some of the pain
how how does it do that okay we got to
think what are we doing when we hit our
head and then we start rubbing our head
we're activating different types of
touch receptors so in that situation
here let's say that we do that we have
the pain right so what's the painful
stimulus let's say here here's the pain
fibers and we're really gonna focus on
it can be see and it can be a delta but
we're mainly gonna be talking about this
with respect to the C fibers but do
remember the a delta R just is important
in this - just the C fibers control more
of this regulation okay so let's say
that there was pain right so there was
some type of painful stimulus or some
type of extreme temperature stimulus and
these were activating these fibers right
and from that it was activating me
peripheral processes then the central
processes and we said that the C fibers
particularly they go to a specific part
in the spinal cord remember the Rex
lamina we divided them into different
like partitions there was a specific one
right here it was called lamina - okay
and lamina - has a special nucleus right
here a special nucleus and right here is
this nucleus this guy is important
because in lamina - the rex lamina -
there's this special structure here
which is called the substantia gelatin
oza of Rolando and then from here we'll
activate some more axons and then cross
over here and move up right through the
anterior lateral system so we know that
there's a pain and temperature pathway
mainly regulated by the C fibers that
we're going to talk about going to
lamina - that's important and again what
is that lamina - a trex t' lamina - is
going to be called they call this the
substantia gelatin oza
of rolando holy crap
right so there's a lot of that one and
there's another one that I can't sign
apps on this is the main one there's
also the nucleus propria switch is in
Rex land on a three button main one here
substantial gelatin nose of Rolando so
now we know this pain pathway now
something I didn't discuss in the pain
pathway the actual video we talked about
the spinothalamic tract and I'm just
gonna mention it really quickly here
let's say here I have C fibers which are
represented here in red so here's my C
fibers and then over here which I want
to do in this baby blue is going to be
my a delta fibers okay they come into
the spinal cord right we know that these
guys come into the spinal cord and they
sign apps on some second-order neuron
and then crossover same thing over here
with the actual C fibers they come to
some second-order neuron and crossover
well the question is that we have to be
able to ask ourselves is what chemical
is actually being released in this
synapse
cuz that's important because it actually
determines a little bit of why fast pain
is fast and why slow pain is slow so
these C fibers are regulating slow pain
and they believe that the chemical that
is released at the synapse point is a
chemical called substance P okay
substance P is important in the synapse
to stimulate these second-order neurons
to go and actually send up through the
ascends through the anterior lateral
system but what about the chemicals with
the a delta fibers what chemicals are
they releasing to actually stimulate
this second-order neuron and then send
the action potentials upwards because
again they're going up and going up
here's the anterolateral system this
chemical that they're releasing into
that synapse is called glutamate and
this one causes excitation a lot faster
and a lot heavier this substance P is a
little bit of a slower activation
substance P you know what else is it's
important for it's also important
because you can release substance P
wherever there's stimulus remember the
stimulus for this was pain
and temperature these were the stimuli
here what's important here is that the
chemical factors that are actually a
cause that actually released like
they're from histamine and protons and
potassium and all that stuff what's
really important is that substance P can
actually be released down here too and
what it does is substance P through
what's called an axon reflex it can be
released out there where all these
chemical mediators are and what it can
do is it can actually decrease the
threshold for pain okay so we can
decrease the threshold needed to
activate the noisy acceptors and
transmit the pain that's really cool
okay so now that we understand that
these are the chemicals that are
released through those synapses for the
slow pain pathway at substance P for the
fast Bane pathway its glutamate let's
come back over here for a second we said
if we hit our head we're gonna send this
action potential upwards now I start
rubbing my head out hurt what am I going
to activate I'm gonna activate a bunch
of different touch receptors let's do
these in orange so here is going to be
some touch receptors let's say that it's
going to be some type of touch receptor
or coming from a pressure receptor
whatever right something like this these
get activated by me rubbing my head and
touching that right when it does that it
sends these action potentials into where
the poster Gary horn they go into the
posterior horn and where do these fibers
usually go for the pacinian corpuscles
the meissner's corpuscles all those guys
if you know they go into the dorsal
column and ascend upwards as the
fasciculus chrysella circuitous but
something's really cool they give off
little collaterals they give off little
collaterals that can come over and
actually stimulate a little inhibitory
neuron and we're gonna zoom in on that
and see how that actually works so we're
gonna come over to this cross-section of
Bionicle but I want you to remember that
whenever we hit our head we have a
painful stimulus a way that our body can
control that pain at the gate
the spinal cord is by rubbing that area
and by rubbing that area caressing the
area it can cause those fibers that are
going into the dorsal contract to give
off collaterals let's look at that so
let's say here was our pain fiber all
right it's bringing information into
substantial gel tones of Rolando and
then from here this guy is going to
cross over right we know it'll go
through the anterior commissure then we
said over here was going to be for the
touch for pressure maybe even a little
bit of stretch receptors or vibration
receptor stuff like that they're gonna
come in and they're going to go into the
dorsal column and ascend upwards right
they're going to go up eventually up to
the medulla where they'll become a part
of the medial meniscus eventually but
what happens is we said that these give
off collaterals they give up these
collaterals there's these little inter
neurons there's these little inter
neurons right here and this Rex lamina
right in again what was this Rex lamina
right here if we said it was Rex lamina
to where the substantiate gelatin oza
over Lata is if you have a lot of
stimulation due to the touch okay a lot
of touch stimulating these fibers what
are they going to do some of the action
potential is going to spill over into
this collateral when it spills over into
this collateral it's going to stimulate
this little inhibitory neuron when it
stimulates that inhibitory neuron guess
what happens that inhibitory neuron
starts releasing certain types of
chemicals what type of chemicals you ask
mainly gaba
okay so they start releasing chemicals
into the synapse called gamma amino
butyric acid and what that does is is
that inhibits it can inhibit two points
it can either inhibit the actual the
substantia gelatin oza where the nucleus
is the actual cell body is or it can
inhibit the actual synaptic terminal so
this actual synaptic bulb here of this
incoming neuron that's the central
process from the dorsal root ganglion
right either way if you inhibit that can
the action potentials that are being
sent from
his pain pathway these pain fibers this
is from pain and temperature right these
are being sent down this if you inhibit
this pathway what's going to happen to
the pain pathway the pain information
that's going over and up you're going to
decrease the action potentials if you
decrease the action potentials what's
that gonna do for the actual paint it's
going to decrease the actual severity of
the pain so this is going to try to
decrease pain perception I think that's
so cool
alright and this should make sense it
should make sense
okay so again with this part remember
that this part here was for the dorsal
column medial meniscal pathway and it
gives off little fibers collaterals that
stimulate these in little inhibitory
interneurons which can send released
certain types of inhibitory chemicals
like gaba to inhibit these neurons from
sending action potentials through the
anterolateral system modulating the pain
so that's called our gate control theory
alright sweet deal so we have that and
again recap it who is controlling this
dorsal column medial meniscal pathway
this was important because of their
collaterals so now we have to talk about
this descending analgesic system there's
so many different structures here that
are controlling this actual are
modulating the pain at the spinal cord
level a couple of them that we're gonna
talk about here is the perry a quid
ductile grey matter we're gonna talk
about this when we diet when we
illustrate them in the diagram we refer
to as PA G period echo dr. gray matter
another one is the peri ventricular
gray matter probably mark they says P V
G periventricular gray matter and then
there's another one here which is going
to be called the locus coeruleus and
some other ones here like the reticular
formation and we'll talk about another
one which is going to be the raphae
nucleus Magnus all these are really
really important gray matter structures
that I can control these descending
fibers so let's go ahead and talk about
those alright so a little bit of
neuroanatomy here's our thala my alright
so here's the thalamus now in between
the thalamus is actually going to be
this little cavity and this little
cavity here is called the third
ventricle so this is our third ventricle
there's pieces of gray matter right
around it so what do you think is called
peri ventricular gray matter fun simple
so these are really important so you
have the peri ventricular gray matter
they're gonna send these descending
fibers down now another thing what does
this structure right here
well this structure here is running
through the midbrain and it's the
continuation of the third ventricle
alright it connects it to the inferior
you there's the fourth ventricle this
structure right here is called the
cerebral aqueduct this blue structure
here well there's actually some nuclei
that are surrounding this cerebral
aqueduct so what do you think they're
called they're called the periaqueductal
gray matter and that's these little red
guys here alright so you have the
periaqueductal gray matter and the
periventricular green matter what these
guys do is they can send some fibers
down but they actually come over here
and they can activate a whole bunch of
other different types of nuclei what are
some of these other nuclei let's say
over here in the midbrain in the
midbrain you have these other structures
here and this is going to be these guys
are really really rich and
epinephrine they're rich in
norepinephrine and because they're rich
in norepinephrine these guys here this
is where we find what's called the locus
coeruleus all right now the locus
coeruleus is gonna get stimulated by the
periventricular grey matter the pair you
collect a grey matter right so again
what were their structure here this was
a periventricular grey matter and that's
when I here's the periaqueductal grey
matter they might be able to stimulate
this locus coeruleus right what else you
know there's other stimulations that
they can give to right here they have
the reticular formation the reticular
formation also has some special nuclei
that are located there and these guys
got a heck of a name this one right here
but actually the nuclei in this area is
called the para giganto celulares
reticular nuclei okay so you have the
pair of giganto cellular is particular
nuclei located within the reticular
formation these are important and again
why because these guys are actually
going to be rich in another type of
neurotransmitter which is called
serotonin okay so they're rich in what's
called serotonin also called you can
call it 5-hydroxytryptamine now there's
one more area which is also important
the perio doctor grey matter can also
give stimulation to these nuclei these
green nuclei are actually called the
raphe nucleus magnus so what would you
call these ones the Roth a nucleus
magnus these are some funky names right
but these are also going to be rich in
serotonin okay so you have the locus
coeruleus which is rich in
norepinephrine and you have the raphe
nucleus magnus and the pair giganto
sailors say layers reticular nuclei
they're rich in the serotonin
neurons now either way let's bring these
guys together okay and let's bring all
of these guys together down here because
they're gonna descend right to this area
here okay now when they descend they
actually go through a part like the
posterior lateral aspect over here in
the lateral white column and then they
come down and they synapse on those cell
bodies where the substantia gelatin oza
of rolando is so again all these fibers
can come down and sign apps right down
there and they can release what type of
chemicals accordingly if we're talking
about the locus coeruleus this is going
to be Noro epinephrine releasing neurons
and if we're talking about the pair
giganto solaris and the raphe nucleus
Magnus these are releasing what's called
5-hydroxytryptamine also known as Cerro
tonin now what happens here they go down
here and they secrete that serotonin in
that five hug us serotonin and
norepinephrine onto little inhibitory
neurons so how let's come over here and
see so since we've occupied a little bit
of this area let's occupy this other
area now okay so now we're going to come
over here and let's pretend for a second
that now we're going to have that pain
fibers are going to be coming in over
here now
so let's say here is going to be the
pain fibers coming in from this side
right activate it through some type of
painful stimulus comes in synapse is
here on the cell bodies of the
substantial gelatin nodes of rolando
cross over and then a ascends right
through the anterior lateral system or
the spinothalamic tract now over those
guys here we have the pair giganto
celulares from the actual reticular
formation we're gonna have the Roffe a
nucleus Magnus
and we're gonna have the locus coeruleus
fibers coming down here and releasing
what type of chemicals they're gonna be
releasing norepinephrine and
5-hydroxytryptamine you know what they
release it on there's little inhibitory
neurons little inhibitory neurons here
let's say it's right here this little
inhibitory neuron is going to be
stimulated by the norepinephrine and by
the 5-hydroxytryptamine and guess what
it's going to do it's gonna come over
here and it's gonna see create special
chemicals very very special chemicals
these chemicals that is going to be
secreting is going to inhibit the
substantia gelatin owes over Londo from
sending action potentials down and if
there's less action potentials being
sent up through this system then what's
going to happen to the pain perception
it's gonna decrease now what are these
chemicals that it's releasing and the
reason I'm telling you why it's why we
need to know these chemicals is because
you know there's chemical that we give
usually to people to help to alleviate
pain like morphine well these chemicals
that are being released here are very
very similar to morphine what are some
of these chemicals that they're
releasing there are releasing what's
called in Kathleen's endorphins and
another one called Dyne orphans all
these chemicals are basically like
natural opioids basically things are
basically our endogenous meaning that
you make them inside your own body
opioids
okay these are endogenous opioids so you
have a way to be able to reduce pain
okay now the question is that you guys
should have is we know how to modulate
pain but how do these nuclei know when
to fire that's important to ask yourself
how do these nuclei know when to fire
these action potentials downward to
inhibit these actual neurons that are
sending action potentials upward it's
the ones that are going up so remember
if we have the fibers coming up here
pretend we have the anterior lateral
system coming up right here so here's
your anterior lateral system ALS right
some of these fibers you know this
what's called the spine Omi's and
cephalic fibers the spine oh Mazen
cephalic fibers they were coming off of
that anterolateral system or the
spinothalamic tract they can stimulate
the periaqueductal gray matter so lots
of action potentials coming up - this
means that there's a lot of pain so that
means that you should stimulate this guy
to give descending pathways to help to
modulate that pain and then this should
make sense what else upper higher brain
structures what kind of structures so
some of the structures that can
influence these guys - periventricular
and the periaqueductal what are some of
them some of them is going to be the
actual limbic nuclei so some of the
limbic nuclei for example if you're with
a cingulate gyrus the insular cortex the
hypothalamus there's so many different
structures that can come down here and
regulate the periaqueductal gray matter
what else parts of the cerebral cortex
maybe even the sensory cortex the
sensory cortex can send down information
here so even the sensory cortex has the
ability to let the periaqueductal gray
matter know sensory cortex okay and then
let this peri o'clock the gray matter
know when to fire action potentials
downwards and these Perrigo dr. gray
matter and periventricular gray matter
they also can release in Cathal ins
alright so different types of endogenous
opioids so what are three ways that you
could actually stimulate this descending
pathway one is through this
anterolateral system where the spinal
attractive is coming off words you can
give off fibers what type of fibers
spino means in cephalic fibers what else
sensory cortex can also tell the gray
matter okay just fire some information
down other limbic nuclei like the
hypothalamus or the anterior in some
insular cortex or the cingulate gyrus
they can tell it also so it's a
beautiful beautiful system hi guys so
that pretty much covers everything that
we need to know about pain modulation I
really hope it made sense I truly do if
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until next time
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