Voiceover: In this tutorial,I'm going to talk about somatosensationtheperipheral nervous system. Somatosensation refersto senses of the body. That includes a wholebunch of different senses, but I like to think aboutfive sensesparticular, which turn out to be reallyuseful for medical purposes because we can test them on examination. The first of these we call position sense,
by which we mean theposition of body parts relative to each other. For example, if you close your eyes and somebody lifts yourarm above your head, you can feel that your arm has been moved. You don't actually haveto see it to know that. Another sense of thebody is vibration sense. If we come into contact
with anything that'svibrating we can feel that. We often use little tuning forks when we're examining patients, to see if they have normal ability to feel something vibrating. The next sense is touch. I'm going to write thatin a different color, and I'll come back to why I'm using
these different colorsa minute. Then we have pain and temperature. Temperature. Let me just write a little quot;Rquot;here to represent a receptor for one of these types of somatosensation, because to be able to senseanything, you need a receptor. Something that can detectthat type of stimulus. There are many different types of
somatosensory receptors, and we lump them into a few different egories. The first big egory ofsomatosensory receptors respond to physical forces, so we call those mechanoreceptors, because they respondto mechanical stimuli. Mechanoreceptors. Receptorsthe egoryof mechanoreceptors
can detect the position of body parts, relative to each other,and vibration, and touch. Then there are other receptors for the senses of pain and temperature, which I'll just representwith a bit quot;Rquot; here. Somatosensory receptors thatcan detect noxious stimuli, that can create the experienceof pain, we call nociceptors. Nociceptors.
Pain and Temperature
So two senses that are extremelyimportant for our survival are our sense of pain andour sense of temperature. And, of course, we havemore scientific terms for pain and temperature. So pain is known as nociception,and temperature, our ability to sense temperature, isknown as thermoception.
So how is it that we're ableto sense pain and temperature? Well, just like allof our other senses, we rely on a veryspecialized type of receptor foundvariouscells throughout our body. Andthis case,orderfor us to sense temperature, we rely on a receptor knownas the TrpV1 receptor. And interestingly enough,this TrpV1 receptor is also sensitive to pain.
And we're going to gointo how this receptor is able to recognize when there'ssome kind of painful stimulusthe environment. So over here, I have alittle representation of what the TrpV1receptor looks like. And this is not youdon't need to know this, you don't need to memorize this. This is just to give you anidea of what it looks like.
It's a very complexstructure, and it's actually loed withinthe cell membrane. So you have cells that aresensitive to temperature and pain loed throughoutyour entire body. And within the membraneof each one of these cells are thousands of theselittle receptors. And how this receptorworks is whenever there's a changein temperature
so let's imagine that youplace your hand on the stove, so there's a little fire. I know you can't see that. So let's imagine that there'sa little fire under here. The heat actually causesa conformational changethis protein. And basically what aconformational change is, is just a changethe physicalstructure of the protein.
So you can imagine that wethe protein was a little box. And you apply heat to it. Maybe we'll make itlook like a rectangle. So this is the general ideabehind a conformational change. So when heat is appliedand also when pain applied via a particular molecule, youhave a conformational changethe TrpV1 protein. So let's look at adiagram of a hand