Pain and temperature | Integumentary system physiology | NCLEX-RN | Khan Academy
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Pain and temperature | Integumentary system physiology | NCLEX-RN | Khan Academy

So two senses that are extremely
important for our survival are our sense of pain and
our sense of temperature. And, of course, we have
more scientific terms for pain and temperature. So pain is known as nociception,
and temperature, our ability to sense temperature, is
known as thermoception. So how is it that we’re able
to sense pain and temperature? Well, just like all
of our other senses, we rely on a very
specialized type of receptor found in various
cells throughout our body. And in this case, in order
for us to sense temperature, we rely on a receptor known
as the TrpV1 receptor. And interestingly enough,
this TrpV1 receptor is also sensitive to pain. And we’re going to go
into how this receptor is able to recognize when there’s
some kind of painful stimulus in the environment. So over here, I have a
little representation of what the TrpV1
receptor looks like. And this is not– you
don’t need to know this, you don’t need to memorize this. This is just to give you an
idea of what it looks like. It’s a very complex
structure, and it’s actually located within
the cell membrane. So you have cells that are
sensitive to temperature and pain located throughout
your entire body. And within the membrane
of each one of these cells are thousands of these
little receptors. And how this receptor
works is whenever there’s a change
in temperature– so let’s imagine that you
place your hand on the stove, so there’s a little fire. I know you can’t see that. So let’s imagine that there’s
a little fire under here. The heat actually causes
a conformational change in this protein. And basically what a
conformational change is, is just a change in the physical
structure of the protein. So you can imagine that we–
the protein was a little box. And you apply heat to it. Maybe we’ll make it
look like a rectangle. So this is the general idea
behind a conformational change. So when heat is applied
and also when pain applied via a particular molecule, you
have a conformational change in the TrpV1 protein. So let’s look at a
diagram of a hand and go into this in a
little bit more detail. OK, so here we have a hand. And as I mentioned
before, we have cells located
throughout the hand. And these cells are sensitive
to temperature and to pain. And within these cells,
there are TrpV1 receptors. So let’s imagine that
each one of these cells sends a little projection
to a nerve that eventually reaches the brain. So these cells, whenever
they are stimulated by either a change
of temperature or the presence of some
sort of painful stimulus– so we keep saying
a painful stimulus. So what can that be? So let’s imagine that
something pokes your hand. So let’s imagine that
we have a sharp object, and it pokes your hand. What happens is, the
cell, when it gets poked, thousands of cells
get broken up. So the cell gets broken up. And when it gets
broken up, it releases all kinds of
different molecules. And these molecules
will travel around. So let’s imagine it releases
this little green molecule. It will travel
around, and it will bind to one of the
little TrpV1 receptors. And when it binds
to a TrpV1 receptor, it causes the same
conformational change that a change in
temperature causes. And so that conformational
change actually activates the cell, and
the cell will send a signal to the brain. So this nerve over here actually
contains three different types of fibers. So there are fast,
medium, and slow fibers. And let’s go into why we
have three different fibers. So fast fibers are really,
really fat in diameter. So we have these
really big, fat fibers, and they have a lot myelin. So they are covered in myelin. And what myelin is,
it’s an insulator that basically allows the
cell to conduct an action potential very quickly. So as an action potential or as
a signal travels down the cell, if we have a lot of myelin
surrounding the cell, the signal is able to
travel really quickly. And another way that a signal
is able to travel quickly is if the cell has a
really big diameter. So a big diameter
lowers the resistance. So you have less
resistance and you have greater conductance
because of the myelin. And these two things
produce a very fast– a cell that is able to produce–
send a signal pretty quickly. So these types of fibers
are known as A-beta fibers. And these fibers are able to
send a signal really quickly to your brain
saying, hey, there’s some sort of change
in temperature. It’s really hot, or
there is something that’s painful, and
allows you to withdraw your hand from that painful
or really hot stimulus. We also have medium fibers. And basically
these medium fibers are a little bit
smaller in diameter. So they might be about this big. And they have a little
bit less myelin. And since they have a
little bit smaller diameter and a little bit
less myelin, they don’t conduct a signal as
quickly as these fast fibers. So these medium diameter fibers
are known as A-delta fibers. So these A-delta
fibers are also found in this big nerve that
goes to your brain. And there’s one
more type of fiber. So there’s a slow fiber. And this slow fiber– I’ll
draw it out over here– is really small in diameter,
and it’s unmyelinated. And so this sends a
signal very, very slowly. It does get your brain,
but it takes a lot longer for the signal to
get your brain. So one way that we could
conceptualize these three different fibers is if you think
about touching a hot stove. Your hand quickly moves
away from the hot stove. So this is this really
big A-beta fiber activating to get your
hand off the hot stove. Then you feel this really
quick sensation of pain immediately after you
touch the hot stove. So that’s this A-delta fiber
sending a painful stimulus to your brain. And for minutes to maybe
even hours after you’ve removed your hand
from the hot stove, you feel this lingering
sense of pain. You feel this burning sensation. And so those are these C fibers
that really small in diameter and unmyelinated. So we went into
how temperature can induce a conformational
change in this TrpV1 receptor and how that conformational
change can cause a cell to send a signal to the brain. So let’s go to how pain
can do the same thing. So whenever you
eat a jalapeno, you might have notice that you
get this– you start sweating. Everything feels
like it’s burning. And you basically have the
same physiological response that you would if it
was really hot outside. And that again is because
this temperature receptor is the same receptor
as a pain receptor. So when you eat a jalapeno–
I’m drawing a little jalapeno. When you bite into the
jalapeno, again, you break the cells apart. And the cells contain a
molecule known as capsaicin. So I’ll write that down
over here– capsaicin. And this capsaicin molecule
exits the jalapeno cell and travels around
until it binds to a TrpV1 receptor
in your tongue. So this is a TrpV1
receptor in the hand, but let’s imagine that
it’s in the tongue. And it triggers
the same response that a change in
temperature would. And so your body reacts
to this capsaicin molecule in the same way
that it would react to a change in temperature. So if it was really hot outside,
you would start sweating. You’d feel this
burning sensation. And so that is why when you
eat a really hot chili pepper you have that type of response. So in summary, we
have our ability to sense pain, which is
known as nociception, and our ability to
sense temperature, known as thermoception. And these two senses rely
on this TrpV1 receptor that is found within various
sensory cells located throughout our body. And the TrpV1
receptor is activated by changes in temperature and
by molecules, such as capsaicin, or by molecules found
within dying cells. And it can activate
this TrpV1 receptor and send a signal to your
brain, letting your brain know that, hey, there
are painful stimulus, or there’s a change
in temperature, and allows you to
react to that stimulus.

About James Carlton

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14 thoughts on “Pain and temperature | Integumentary system physiology | NCLEX-RN | Khan Academy

  1. Is it a coincidence; we just learned about those receptors and you uploaded a video about the same subject really interesting 🙂

  2. It's interesting how the cell contents of certain plant species (the capsaicin molecule) are natural analogs for the molecules detected by the body's own pain receptors. (I expect there is an evolutionary connection to account for it.)

    When you stick your toe under sub-scalding temperature water at a precise temperature (about 54C) it actually 'feels' like chilled water instead of hot. Can this observation be explained from the interactions of the different thermoception signals?

  3. I've been looking an explanation for a some time. What I find fascinating is how these receptors are perfectly calibrated so to speak.

  4. Sorry, but all the sources I use suggest that "A Beta fibres", (the really fast ones), are NOT involved in the nociception.

    Aside of that, beautiful explanations!

  5. Not really a question that contributes to the content. But I really can't figure out of which food you're talking about 😉 I suppose that it is a sort of chili pepper, your "holopaynio"?

  6. You talked about A beta fibres sensing pain but that's incorrect. A beta fibres only sense non-noxious stimulus. Due to faster transmission they can actually be stimulated to to flood the relevant T cell that the A delta fibres are crossing acting as a pre synaptic inhibitor and thus relieving pain.

  7. For 3yrs I've been dealing with this issue of pain & temperature on
    my LEFT side of my body – pretty much from the bottom of my skull down
    to my toes & only the left side. I can't feel heat & cold on
    the left side! I feel PAIN instead. "Warm" seems to not bother me. I
    also have a decreased sense of touch on my left side. My left hand
    doesn't seem to be as affected as the rest of the left side of my body.
    Maybe because my hand is always touching things? But I still have the
    decreased sense of touch in my left hand & the increased pain but I
    can sense some temperature in my left hand, but it isn't as it should
    be. So when I'm getting a bath ready for my kids, I have to use my
    right hand to see if it's too hot or cold. No doctors have been able to
    tell me what this is or why this is happening. 🙁 Why is this

  8. Pain does not equate to nociception. This is the Cartesian model of pain and has been thoroughly disproven. Very disappointing. Google "biopsychosocial model of pain" if you really want an explanation of how pain works.

  9. Thank you sooo much. You guys are brilliant at explanations. Keep things flowing as we really do appreciate your kind work.

  10. Are the fast, medium, and slow fibres the same as the fast-adapting, slow-adapting, and non-adapting receptors discussed in the somatosensation KA video?

  11. makes sense that chili peppers effect these receptors in our body. Chilis are spicy to eat (pain) and they make us feel warm. (Scoville heat units)

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