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Raja Narayan 创建




the next mechanoreceptor is called pacinian corpuscle so pacinian x' and this is another corpuscle another body we're going to talk about right here and again we'll have some external stimulus right here could be somebody poking you or some other type stimulus it's transmitted deep into our skin pacinian corpuscle will respond it looks like this and it's also known as the onion layered mechanoreceptor and you can kind of tell why right because there are a whole bunch of layers here and another term for pacinian corpuscle is the lamellar corpuscles and lamella just means a layer so there are many lamella around here in fact that's an important term so I'll write it here lamella so this is a lamellar corpuscles also kind of a fun word to say and so notice all of these layers here what happens is that when we have this force transmitted deep into our skin we'll have let's say this layer here I'm trying to outline right there that layer will stay still but the layer immediately outside of it that I'm outlining right here and so this outer force right here will cause this outer ring right here to respond by spinning it'll kind of turn this way relative to the inside disk and compared to my snares corpuscle above in order for this disk to move in this direction and relative to this inner disk right here we would require a little more significant of a stimulus so we'd want something like a push or a poke to cause this disk to move relative to this disk and it'd be the same thing as what we saw earlier with my sinners corpus colette when one disk move past the other there's an opportunity for sodium to enter this ring and this ring is also an epithelial cell that's been specialized and they're all kind of these concentric rings that lead into the middle and what do you think sits here right dab in the center well if you guessed and 1/2 errant nerve fiber you are absolutely right and so the sodium ions will kind of go through between these rings or these epithelial cells to get to the center and eventually that would be a lot of sodium building up in afferent nerve fiber thus generating an action potential that will be sent to our central nervous system and so all this began from kind of a significant stimulus like a push that means that pacinian corpuscle likely perceives deep touch and it's deep touch of Harry and non-hairy skin and an example of that would be kind of what I drew up here that's just going to be a poke so very strong poke not like what you see on Facebook but when someone actually pokes you in real life would cause this type of stimulus and as we mentioned above with my Sanders corpuscle we're going to have this exact thing here and I'll just kind of copy paste it in that we're going to require constantly changing stimulus to keep on firing and sending a message to the central nervous system and this makes sense right because when we're taking the subway to work or school and there's so many people that people just have to kind of be like pushing and shoving together to fit in one car you won't even notice that someone's pushing against you after some time and finally if this is going to be sort of a significant stimulus that perceives deep touch we can deduce then that pacinian corpuscle will sit lower than mice nurse corpuscle and sure enough it's found deep in the hypodermis or the subcutaneous tissue sometimes so it's pretty deep there and as we move further along we can talk about the next mechanoreceptor that is called Merkel's disk so Merkel's disk we've been talking about corpus goals all this time but now we'll just talk about a single disk and our stimulus will be the same if we have some type of external force right here that kind of pushes and transmits this force deep within our skin will have Merkel's disk respond and I don't have a fancy picture for it and that's because Merkel's disk is actually just a specialized keratinocyte or an epithelial cell that's not unlike the regular cells that you have in your epidermis so it kind of sits in your epidermis as we'll talk about too so it kind of looks like this Muniz I'll mention in a little bit this also has an afferent nerve fiber that sits right there and the reason why we have all of these little vertices right here is because Merkel's disk holds a whole bunch of vesicles you might remember that term vesicles which are just rockets that have membrane around them that's sitting within the cell these pockets hold a neuropeptide so I'll draw a little neuropeptide in each of them and you've probably heard of neuropeptides before it but it's just a peptide which is a string of amino acids that talk to the nervous system so I'll label that this is a neuro peptide sitting within our vesicle in our specialized epithelial cell the Merkel's disk and what I'll draw down here is a little receptor and so I'll just write this is going to be in N just to be a neuropeptide NP receptor just to abbreviate cuz I don't have that much space that's an NP receptor and so what will happen is that when we have this force transmitted right here it actually causes the vesicle to open up and so this kind of splits open right there and allows the neuropeptide to be liberated and it's going to be present within the cell kind of floating around and then over time it'll come and sit down right here and when it lands on the neuropeptide receptor will actually start having ion channels open so ion channels should signal sodium ion channels will open that allow sodium to enter Merkel's disk and eventually make its way into this afferent nerve fiber and that generates the action potential that'll go communicate with our central nervous system and with Merkel's disk like we mentioned this is just a specialized keratinocyte or an epithelial cell it's just like what we have sitting in our epidermis so much so that it's located itself in the epidermis it's found in the stratum basale and sometimes it could be even lower in the the papillary dermis so it's in the interface between the stratum basale of the epidermis and the papillary dermis so I'll write two here to emphasize it's in between these guys and so the trick is that if you remember that this is a specialized care to no site like what's in the epidermis you remember then that it sits pretty high up in the stratum basale to the papillary dermis and so it's responsible for perceiving light touch light-touch this is gonna be on both Harry and non-hairy skin but it's different from Meisner scorp uh school because this is sustained light touch so this is something that's going to keep on firing as long as you have the stimulus present and that makes sense because when the stimulus is there and it's causing this sensation as long as the neuropeptide is connected to this receptor we're going to keep on having these ion channels open and the sodium coming in and generating the action potential and remember it's sustained light touch okay so as long as the stimulus is there we're going to keep on noticing it