So, let's take a look about the [INAUDIBLE] in the fiber's response properties, okay. So for this one, let's take a look, okay? So, for the touch sensation, they are some of those fibers actually responds to very low threshold this mechano receptor. That means actually, you just need a gentle touch and then they can detect it, okay. So this called low threshold mechano receptor LTMR. And among them this is actually the mucous cell. The LTMR and also they are slowly adapted SAI that means slowly adapted take look the list of bones. If you recall from these axiom okay? You'll actually recall the file and then you give the scheme a push like here. And then you'll record, recording will show his dead cell. Actually at the beginning of the stimulus [INAUDIBLE] of an action potential. And then, maybe gradually decrease the frequency. There is a response stimulus. That [INAUDIBLE] actually, slowly adapting LTMR, okay? This response stimuli and interpretation and also for this roughly, this one. For this ,roughly, the ending. They also are similar slowly adapted. But take a look at the other one, like this guy. This is with this one. It's this one. [FOREIGN] This line so special, take a look. If you have stimulus and the at the beginning and at the end of the stimulus. So during this stimulus actually, they don't care. This is called rapidly adapted. So, at the beginning you have response. And then the cell, just quickly adapted to the stimulation, no response at all. But the way you release stimulation, again, responding to you, right? These two type of cell of course then, will response for those kind of gentle touch, okay? But for this cell, then mainly response to the high frequency of the stimulation, right? Because they don't care about it's actually how long you pushed the skin. Because there is a time that don't do the push, they were not responding to you. Okay, there is another one. This is type one, rapid adapting, low threshold mechanical receptor. There's another one, this is type two for this one. They're also similar. Just as it was responding to the onset and the offset of the stimulation, okay? For this one actually they responded to as I mentioned because it is sitting there in the deep of this damage. They're responding to really high frequency of the stimulation, okay? And that this one, relatively low frequency of the stimulation, because they sit on the top of this ridge here. There is another type of cells called high threshold mechanoreceptors. That's corresponding to the free ending, like this green one, green fiber. This guy actually, they need really high, strong stimulation, then they can respond. If you use this kind of low intensity stimulation, those neurons will not give you the response. And also, this neuron actually not much adaptation to it, right? What's this? Of for pain right? Because under this situation quite strong stimulation might be dangerous or would damage your skin. And then this guy will report to the brain. This is a painful situation you need to work to protect yourself right? Indeed, this is mainly the fiber. It's [INAUDIBLE] free node ending. It's correspondent to high threshold, receptor. It's quite interesting, right? For these three types of different response properties what correspondent to make this adaptation. What kind of mechanism responsible for the adaptation? [FOREIGN] Take a look here. If you recall from this one, this is the Pacinian corpuscle here. And then if you use a stimulation, push down and the cell will respond, okay? But during this push the cell actually will not give any response. But when you release this stimulation, the cell responds again. Does this property belong to the neuron or to the surrounding structure? People did a clever experiment. Dissect out this new ending and then give the stimulation directly then you can take a look. If we use this push this new ending and the cell that gives the response during this push so deal gives it a response. And the thing it release, no response. So what it tells you then, is this kind of structure, the surrounding structure, has those kind of properties for adaptation and also for the release response or for response, okay? But of course that response is produced by the network fiber. Only the network fiber can give you the response. But because this structure somehow telling you this stimulation pattern, okay? Is it a [INAUDIBLE], okay. So this is kind of [INAUDIBLE] cell neuron response properties. As so we've discussed before, for a sensory neuron, especially another important feature is the receptor field. I'll show you how to determine a neuron's receptive field. For example, in the you when one and then how you would deepen the stimuli to the map to the receptive field. >> [INAUDIBLE] >> The question is actually how to determine a sensory neuron's receptive field, receptive field. We can take one example to discuss this issue. For example if you recall from a. And we know center surround receptor field, right? So, but at the beginning maybe you don't know center surround receptor field. How you doing the experiment, how you probe this kind of a profile? >> [INAUDIBLE] in the surrounding area. >> Yeah good, good so just actually you try to deliver different kind of the stimulation. Maybe at different wavelengths and also maybe intensity, around some certain area, and they check the cell's response. Either the cell will be excited, and then that's called an on response. If the cell was inhibited by the stimulation, that also considered a receptive field of this neuron, right? So this way, we've found actually for the ganglion cell we have the send us around sometimes in the center, maybe excitation. They're surrounding, maybe inhibition or sometimes maybe the opposite way, okay? So to determine the receptive field of these kind of neurons similar strategy. That's what people did, actually, from a human subject. And then you can from those fibers, okay? For example, one fiber actually running into your palm. And then you just actually use some kind of sharp needle to probe the surface of the skin. And to see whether this neuron can keep the action potential firing or not. And by this, then people found the Meissner's corpuscles If this neuron is corresponding to this kind of a neuron type and the receptive field is quite small. What you see is just those tiny spot. But if that fiber is corresponding to these is very different. The receptive field is really large and sometimes covers the whole finger, okay? So that means there should be different types of neurons. The detection, spacial detection are quite different. For the kind of quite subtle detection, you need actually quite some more receptive field. [FOREIGN] Then you need to redefine the receptive field for the detection, right? If you use this kind of strategy to determine, even the skin, the region of the receptive field. Then you will have a map about, or actually it's the receptive field, across the whole body, okay? So you can have a guess on which region actually has the smallest receptive field. >> [INAUDIBLE] >> Face. >> Face. >> [INAUDIBLE] >> Okay, face is still too large. We need to go to the more definite region. The face that you have is a tongue. You have your lips, you have your nose. You have all those areas, right? Lips, right, would be quite actually a small receptive field, right? And also? >> Fingertip. >> The fingertip, right. Yeah, this is what people did, okay. The [INAUDIBLE] actually, you see okay? So this is actually it's how [INAUDIBLE] regions. Okay, so if you have very small receptive field, that means that actually you can read it differentially. The two points actually are how far away the two points? Actually, then you can judge, okay? So, for this one, [FOREIGN] our index finger, they are quite small receptive field, okay? And also for this kind of region [FOREIGN] okay? [FOREIGN] These neurons actually, the stimulation is a kind of mechanical stimulation, right? So then you will think, okay, so how does this neuron detect this mechanical force? The answer will be, it's a mechanical sensitive ion channel. They don't just use the DPKR calcium right? Maybe a mechano gated channel. For this study actually unfortunately the progress is quiet slow, okay? To identify what kind of [INAUDIBLE] receptors responsible for transfuse this mechanical force.
