everyone welcome professor Wong's lectures on anatomy and physiology i'm professor bob long this video is intended for those students that are enrolled in my human anatomy and physiology 2 course at Del Mar College during the summer semesters ok these videos are somewhat timeless though and since that anyone can watch them at any time and learn some information about anatomy and physiology as you guys know we're in the corona virus or Koba 19 shut down my face-to-face courses have been converted to online so that's the reason that I developed this YouTube channel I'm doing these videos so that my students can still get instructional delivery I'm an old-school lecturer so I'm still doing everything writing on a board I as a neurobiologist who studies memory and learning in the brain have a great deal of knowledge of how memory and learning works and I know that when we use our hands to do things we learn better so I like for my students to write and draw along with me I show you completed images you don't learn as well you can learn but it's deeper and graining in the system when you are actually doing something along with me so hence the style this is lecture number it's supposed to be lecture number three in my sensory physiology series but in the last video for some reason the camera stopped for a fraction of a second and then started up again we've been covering the general senses and comparing the general than the special senses if you're following along in my notes set I'm on the bottom of page six for those of you who are in my class we're gonna be talking about the general sensory receptors the different modalities and the types of receptors the first one that's listed nociceptors so we're going to be talking about nociception and if you reading the note set there's some spaces for you to write some stuff in the nociception is the detection of pain or another way we say it is Algie Xia anytime you see Algie Xia refers to pain so someone who is taking an analgesic I mentioned this before but you should know this and means not or anti against analgesic as pain so an analgesic is a pain man if someone is experiencing what we call hyper LG Jie and that's someone who's super sensitive to pain you know every little thing that hurts the normal person could tolerate someone with hyperalgesia experiences an extreme response and therefore they're very very sensitive to pain okay they have an overreaction to pain now when we talk about that those receptors themselves nociceptors pain receptors are considered to be what we call free nerve endings what that means is this and some of the general senses the neuron out of the periphery can either be a free nerve ending or the end of the neuron can be coiled up with some connective tissue and have tissue around it pain receptors nociceptors are free nerve endings they don't have a lot of connective tissue surrounding them okay they are located in a number of regions that we find in the body one area so these are some of the areas where we find these receptors and very high up in the dermis very close to the epidermis okay right at that border so if you remember our study of skin the uppermost layer the skin would be called the epidermis and then the layer below that with a lot of connective tissues and it would be considered the dermis okay well some of our nociceptors are located very very high up in the dermis the axons will come up and sometimes sit right underneath these little pockets or very close up and sometimes extending right up to the very lower levels of that thickness that makes sure that when we hit them we don't have to do a lot of damage to the body to reach them they're very high up in the dermis okay another location for nose receptors they're found very abundantly in our skin they're found in the periosteum my periosteum of bone so when you fracture a bone you tear that periosteum and the nerves that are in that periosteum get torn and those pain fibers send a signal to you it's very painful trust me I know broken a lot of bones they are found in the walls of blood vessels when you cut a blood vessel you know it it hurts it's very painful and they can be found in joint capsules and muscles so whenever you tear a muscle it's painful and whenever you damage the joint or the joint capsule it's pretty painful so we find them in these four areas in great abundance there are also a lot of pain fibers in the internal viscera like having a stomachache or when you're feeling pain in the abdomen one thing to note about the internal pain receptors the ones in the abdominal cavity are surrounding a lot of our viscera of the body there are fewer of those and further between with large receptive fields I mentioned this in some of the last videos but when we are feeling pain internally in the abdomen we can't pinpoint the exact location very often we can give a generalized area if you're feeling pain in your knee you can point exactly to which part of the knee or the knee joint where you're feeling the pain but in the abdomen there's so few of the pain receptors and they're so far apart they have large receptive fields makes it difficult to pinpoint the location of the pain okay now when it comes to nociceptors they can respond to three different types of stimuli they're sensitive to three you know specific types of stimuli one of them is what we call physical or mechanical distortion it so this would be like if you stepped on the nail and you cut the pain receptor or if someone pinches or twists your skin so that physical that physical damage or mechanical damage will set off certain pain receptors they can respond to extreme temperatures so if you ever stuck your hand in an ice chest you know looking for I don't know a soda while you're floating a river because you know you drink cokes when you flow the river if you stick your head in an ice chest then it starts to hurt it gets painful and extreme heat will cause a burning pain okay and there are specific chemicals usually extreme PHS something very acidic or very basic will set off a pain sensation okay now in really extreme pain all of these get set off sometimes you feel they just described as a burning sensation and that's when someone's really feeling a whole lot of pain okay one of the things that's not listed in the note set but I want to mention to you is that one of the neurotransmitters there's there was a neurotransmitter discovered that's utilized by the pain fibers that neurotransmitter by the way is called substance P makes it easy to remember substitute P for pain so that's one of the neurotransmitters utilized in our brain when we're interpreting pain something interesting to note our pain fibers or nociceptors our tonic receptors meaning they're always releasing neurotransmitter they can release more or less depending on types of stimuli but when they adapt we actually undergo and emit some instances central adaptation so the pain stimulus could still be there but somewhere along the sensory pathway we filter it out I think I said in a previous video that they're like phasic receptors that they're either are on or off and that's not under said thank you but nonetheless so finally pain fibers can respond there's two different types of pain fibers we call them type A fibers or axons and there's type C fibers so you should know the difference between the two type A fibers do what we call fast or sharp pain very often this is the pain at the moment of injury if you were say playing tennis and you went to hit a shot and you twist and you hurt something in your knee that information gets communicated to your brain before you complete the motion so that you can remove yourself from the painful stimulus so we call that a very fast or a very sharp pain excuse me it on the moment of injury and I'm gonna erase type-c for a second and rewrite it one thing we know about type II fibers and type C fibers is this I had to move that because I need to put some information in here for Type C fibers they tend to do what we call sorry they do what we call slow and I just can't write right now and I don't want to start this video over you guys have no idea how long it takes to make these videos right so I'm gonna deal with some minor issues here but for Type C fibers they do what we call slow pain or what we would call a dull ache very often this is not a pain that you feel at the moment of injury but you feel this long after the injury it's sort of a soreness and some aches that set in to remind you hey your knees bad don't go try to run a marathon or something they remind us to keep off of it so that we can let the body heal now a few characteristics type-a fibers actually fire very fast action potentials if you remember in part 1 a.m. P we talked about two ways that we can increase action potential velocity one of those ways is to have a much larger diameter excellent if you were to just look at the number of ions like sodium ions that can flow through this bringing a certain amount of voltage milli voltage or charge down the axon I can have a lot greater voltage flow down this axon then I can flowing in this one okay so one thing we know about type a fibers is they have very large diameter axons compared to type C fibers that allows a faster flow of action potential these have a smaller diameter Aksum also type-a fibers tend to be myelinated if you recall about myelination from part one A&P one of the things we know about myelination is these cells called Schwann cells and the p NS anyway and the CNS that would call the little bitter sites wrap around the axon and insulate it and they're interrupted by nodes of ranvier so the axon is actually traveling in here all of the sodium ions that need to flow into the cell through ion channels to conduct that action potential can't access the axon here but if enough of these ions in this area will diffuse through you know passive diffusion and hit some of the voltage here I'm sorry yeah some of the voltage-gated channels at the node of ranvier when that opens I can let a ton of ions flow in and the ions will look like or the voltage will look like it jumps from node of ranvier - no - ROM b8 so these undergo saltatory conduction because they are myelinated where type C fibers tend to undergo what we call continuous conduction because they are unmyelinated so I didn't write all that down but you should know type 8 fibers have large diameter axons and are myelinated so they undergo saltatory conduction and they say very rapid action potentials type C fibers send much slower action potentials because we know the pain that injury happened we just need to be reminded over time so they have smaller diameter axons they are unmyelinated they undergo continuous conduction okay know if you're following along in the notes it - things that we can add to our understanding of nociceptors and again these are just very basic fundamental descriptions to get a fundamental understanding there's a lot more to this but we can spend an entire semester doing in all nothing but pain physiology now there's two different types of pain that we can talk about one I mentioned in the previous video called referred pain referred pain is pain felt in another part of the body or interpreted in a part of the body that is not the location of the stimulus I talked about having a heart attack in people having pain down their left arm so there are some types of pain where we get what's called referred pain you detect the pain in a location of the body that is other than the location of the stimulus and then there's one that's called phantom pain as you know a phantom is a ghost so in phantom pain or ghost pains you're experiencing pain in a limb that's been amputated your hand may not be there anymore someone may have their hand so badly mangled and the nerves were so badly damaged that they continually sense pain there are very there are some instances where that limb can be amputated to remove the painful stimulus if that limbs not usable because those axons are still sometimes sensitized and fire you can feel pain and because our brain interprets the information based upon the labelled line on which it arrives you think you're feeling the hand and the pain in the hand even though it's been amputated so we call pain from a limb that's been amputated a phantom pain know um another type of neuron that's very similar to pain receptors are called thermal receptors as far as their construction film receptors are very similar to pain receptors thermo receptors detect rapid changes in temperature they don't imamat er to check your temperature so thermo receptors do rapid changes in temperature they're also located in the dermis they're free nerve endings and and extreme temperatures can cause them to fire pain signals now the hot receptors and the cold receptors that we can see are actually histologically they look almost identical they look like twins the difference is if I have two thermo receptors a hot receptor and a cold receptor if I increase the temperature the hot receptors will fire the cold receptors won't so some art are sensitive to increases in temperature the cold receptors will respond to decreases in temperature so if you jump in a cold swimming pool the cold receptors fire and you start to feel that coldness if you jump into a hot tub the thermal hot thermal receptors will fire and you'll feel the warmth now thermo receptors are pretty fast adapting and when they do adapt you no longer feel that sensation for example if you jump in a cold swimming pool then you swim around for a while someone else wants to jump in they said no it's too cool you say I just jump in you'll get used to it well that's a type of adaptation you're adapting to the change in temperature ok I'm not going to talk much more about thermo receptors just know that hot and cold receptors are different from each other and their histology and their physical appearance but there are some that respondent rapid increases in temperature so that respond to decreases in temperature and then we're going to get to all the different tactile receptors tactile receptors do touch there's a whole series of tactile receptors although some books don't classify them this way so when it comes to the tactile receptors some of the tactile receptors are going to respond to what we call fine touch ok one of the ones that's listed by the way first there's free nerve endings well we've already talked about talked about the free nerve endings free nerve endings don't have any connective tissues surrounding them and there are two types there are the nociceptors and thermo receptors that we just talked about ok we don't even talk about those anymore there's one called a root hair plexus a root hair plexus and many of these tactile receptors are found in those the dermis of the skin when we look at hairy skin wherever a hair follicle sticks out of the skin these receptors actually come in and crawl around the base or the root of the hair follicle if you stimulate or brush the hairs on your arms that will trigger these so the routier plexus is wrapped around the base of the hair or a hair follicle now if I have several hairs sticking out of the skin and I have three different receptors here if I trick them in this order and will tell me which direction something is moving across the surface of the body if I trip them in reverse order then it tells me something is moving in the other direction so root hair plexus wrapped around the root of a hair follicle and one of the things they can tell us is the direction that something is moving along the body based on their firing patterns okay now I'm gonna try to take it my notes on occasion I don't actually have any notes written in my Hooksett I never look at it it's blank but I do peek at it from time to time even though I've been doing this forever I look down at page simply because I want to try to do these in the same order that they're written in the note set so you can follow along now the next type of receptor that's listed is called a Merkel's disk or Merkel's corpuscle a Merkel's disk is surrounded with some connective tissue there's some wrapping around them and Merkel's disks do what we call finer light touch one of the differences between Merkel's and meissner's a meissner's corpuscle both of these do fine touch or very light touch okay like someone caressing your skin one of the differences is these are found in hairless skin where the Merkel's are found in hairy skin they both do light touch but there are certain parts of the body where we don't have any hair for example the palms of your hands and the soles of the feet have no hair on them so we find meissner's corpuscle x' there they do very very fine or like touch we also don't have any hair on the actual surface of the eyelid itself if you close your eyelids and look at them in the mirror you have very fine hair all over your face and over most of the body but on the actual eyelid itself there's no hair something's going to touch your eyes if there's a bug crawling you want to feel that very light touch and protect yourself we don't find any on the on the lips of the labia there's some all around it like in a mustache or a goatee but not on the actual lips themselves so they're very very sensitive to light touch the actual nipple itself that sticks out of the areola usually as hairless and they're very sensitive define touch and the actual genitals themselves the glans penis or the head of the penis of the clitoris itself don't have any hair on them northern labia are some of the folds of skin around it that makes them very very sensitive to find touch okay Puccini M corpuscles also called laminated core muscles and ruffini's corpuscle a lot of these are named after people that first discovered and described in a lot of books now are changing those names they want to get away from the personal names and come to these scientific terms but a lot of them are still listed this week Puccini and corpuscles and ruffini's corpuscle these both do deep pressure okay and some vibration Puccini and corpuscles and ruffini's corpuscle do a slightly different deep pressure especially the Puccini ins which do a lot of vibration in our skin so if you were you know the new massage guns that athletes used to massage themselves a lot of that vibration and deep pressure is being detected by Puccini immortals ruffini's also do some deep pressure one of the ways I remember them is Eminem are fine like Eminem's a fine chocolate candy although they're not that fine on the chocolate but they're delicious but Eminem meissner's and myrtles do fine okay Puccini ins the PNR are rough okay so they do rough pressure or deep pressure it's kind of an easy way to remember those you can look up some more details on those if you like I'm not going to spend much more time on them because we kids like I said we could spend all day all semester on this chapter for proprioceptors there's two different proprio receptors missing proprio receptors as you know detect proprioception or body position okay they tell us a lot about our body position in space and this was part of mark muscle memory we there's two different types of proprioceptive are found in two different locations there's one called on drawn a blank the muscle spindles and I couldn't think of the word sorry muscle spindle fibers these are going to be found associated with skeletal muscle and they tell us about the tension and stretch in a muscle so muscle spindle fibers tell us about tension and stretching a muscle and then the other one are called Golgi tendon organs these are found in the tendons that attach your muscle to a bone they'll tell us about the stretch and pressure or pool tension is the word I'm looking for they tell us about the stretch or the tension in the tendons that the muscles attach to okay so both of these are telling us about you know tension and stretch and muscles or in tendons that attach the muscles to the joints so they tell us about our body positioning and joint position that's about all i want to say about those when it comes to the next type of receptor we talk about baroreceptors now I mention all of these before in the first election but baroreceptors detect pressures gate changes in pressure and some organs so when it comes to the baroreceptors you certainly would find them in things like the digestive tract the urinary bladder and the digestive tract from the urinary bladder they tell us when we're full so that we either stop eating or you know you have to go urinate or you know you have the urge to defecate so there's pressure receptors and the digestive and urinary tracts that tell us about those pressures but one of the things we haven't covered yet is the cardiovascular system but coming out of the left ventricle so your heart is divided into four chambers the bottom left chamber is called the left ventricle the largest pipe that's going to deliver all the blood to all the tissues of the body is going to come out of this and that pipe is called the aorta the aortic comes out of the heart are just back and then runs down the abdomen and has branches that feed blood to all your organs two of the major branches coming off the aorta the first one as it comes out out of the heart itself it's called the brachiocephalic and it's gonna have a branch it goes up to your head on the other side we don't need this little extension but these two arteries that are coming up towards the head are called the carotid arteries the aortic artery or the aorta and the carotid arteries have little areas in them where we find some receptors one set of receptors these are called the carotid bodies and the aortic body the carotid bodies in aortic mice have baroreceptors when our heart has to undergo sympathetic stimulation and it contracts under a great force the blood shoots out and puts pressure on the walls of these vessels if blood pressure rises too high then some of the very tiny branches downstream cuff capillaries and arterioles can rupture we call those vascular accidents and some forms that are called strokes if you ruptured blood vessels in your brain it would be called a cerebrovascular accident if you rupture some in your heart then they can be cardiovascular accident and if they're in the lungs they can be called pulmonary vascular accidents and when you rupture those blood vessels no more blood can flow to the tissues on the other side of the red and in the brain that causes neural deficits and damage to neurons so our body has a way to measure our own blood pressure if it drops too low we can send signals to the brain of the heart and increase the force of contraction and the rate of contraction to make sure that we'd really be adequate oxygen and glucose and nutrients to our cells if blood pressure rises too high that can be dangerous so we have mechanisms that can feedback any lower heart rate and blood pressure sympathetic and parasympathetic activation of the heart so the carotid bodies and the aortic bodies have baroreceptors that are monitoring our blood pressure okay now one of the last things I want to do before we start moving into the special senses is I want to talk about chemo receptors okay chemo receptors there's two different types of chemo receptors there's chemo receptors that monitor the internal chemical environment they're part of the general senses and then we have external chemo receptors so they're going to be part of special senses for the internal chemo receptors they're monitoring concentrations of a lot of the nutrients and ions in our body for example sodium and potassium play a huge role in action potentials chloride ions play a huge role in so do calcium ions in our physiology so our body is monitoring our salt levels in our blood and kinda at the same time monitoring water levels or hydration for example I take a bucket of fluid some pure water and I dissolve a whole bunch of salt in here sodium and chloride and potassium and life is also sugar in here now I can be measuring the concentration of salt and sugar in this container if I could tap off some of the water and drain it so that I lower the volume of water but I do not alter the concentration of the ions I don't have any ions that exit here then what essentially happens to the salt and the ion concentration is I've increased the concentration of salts and sugar by dehydrating myself so under dehydration or over a cumulation of salt or sugar we can alter our body's concentration of these substances well the internal keyboard receptors are monitoring this we have some of those internal chemo receptors in the hypothalamus of the brain and they're monitoring some of these concentrations we also have oxygen receptors in the carotid and aortic bodies that are monitoring oxygen and carbon dioxide and pH when we don't get enough oxygen to our tissues we're also not reading carbon dioxide carbon dioxide and water can enter into a chemical reaction of carbonic acid and then that dissociates it makes your pH of your blood become altered if blood pH starts to drop too low becomes acidic then our body can be triggered and there's a way that we can trigger mechanisms to restore that we're going to talk about that at this time we will when we do respiratory system and urinary system there's respiratory acidosis and metabolic acidosis if the blood pH becomes too basic then you're in what's called alkalosis and we still need to trigger the brain to fire those mechanisms to restore the pH of the body so the internal chemoreceptors are monitoring ion concentrations nutrient concentrations and sometimes oxygen and carbon dioxide concentrations or blood pH to make adjustments to keep us in our homeostatic range table so that's all of the general senses so we've done three videos so far we've done an introduction to the sensory system and a comparison of the general senses the second video was a continuation of that it was supposed to be one long video but fortunately the cameras broke it up for some reason it worked out to our advantage and now that we've done all the general sensory modalities this again was a very brief and rough introduction you do need to go in and read the chapter of the book and read up a bit more about these no I'm gonna cut this video here and remove on to the special senses and we'll do several videos on the special senses because there's a lot to cover so I hope you learn something I hope you had as much fun as I did and I'll see you on the flip side in the next video thanks for watching