okay welcome to glomerular filtration rate so we're just going to pick up where we left off from the last video and here we go all right sorry about that okay all right so let's go back a slide just to pick up um there we go all right so um oh get rid of me all right so um real Auto regulation so Auto regulation means that the kidney is going to take care of things itself so we are going to function just at the nephron level and we are going to act on just individual nephrons so um notice it says that this is um the intrinsic ability of the kidney okay to this is the kidney is doing its on its own and like I said it's the nephrons that are doing it right at the nephron level it's not anything more involved um physiologically speaking or anatomically speaking so um we want to maintain a constant blood pressure entering the nephron or entering the glomerulus and that will ensure that we have a GFR of 125 milliliters per minute and I'm just going to write that in there again some places you may see 120 to 125 we're just going to go with 125 because that's what I've been doing for the past bunch of years all right so um this Auto regulation mechanism is going to maintain what's happening the kidney regardless of what's going on around you um in outside of the kidney so what's going on in your body you're being chased by a Rottweiler you're exercising you're laying down uh whatever you're upside down I don't care but whatever changes in systemic arterial blood pressure happen they are not going to have an effect on the kidney because you would have too great of a fluctuation too rapidly um that would then really mess with your body's ability to maintain water and electrolyte balance pH and all that kind of stuff so we don't want that we want to maintain homeostasis all right so two mechanisms we're going to do and one of them we kind of already talked about is the myogenic response or the myogenic mechanism and the other one we're going to do is to be local Marilla feedback so let's take a look at myogenic all right so um vascular smooth muscle has an inherent quality that if you stretch it it will contract so um it says myogenic response contraction relax relaxation of smooth muscle of Affair and arterial in response to stress stretch not stress so um vascular smooth muscle vascular smooth muscle will contract if we stretch and it will relax if we relax okay so if there's too much pressure some of this would be high hydrostatic pressure or high blood pressure coming into the afferent arterial then we're going to vasoconstrict then if the pressure is low if we get a drop in systemic blood pressure or a drop in and the pressure that's affecting um the afferent arterial then it'll relax and vasodilate oh let's put this so we get Vaso oh it's in this down here so decreased blood pressure so we're like taking a look at this one right here um less stretch the smooth muscle in the arterial causes the smooth muscle cells to relax the vessels will dilate allows more blood into the glomerulus and so then we'll get an increase in hydrostatic pressure and that increase in hydrostatic pressure the glomerulus will compensate for a lower systemic blood pressure so maybe you're laying down then you're asleep or you're prone or your supine or whatever so you're laying down and um so your blood pressure is going to be less and uh but yet you still want to keep up the same amount of filtration and so what you're going to do is vasodilate and more blood will enter the glomerulus and that will raise hydrostatic pressure and GFR will remain normal okay so with low blood pressure low systemic blood pressure we're gonna vasodilate to increase hydrostatic pressure and to increase GFR I think make sure that it stays where it's supposed to be now what's going to happen if you have an increased blood pressure you'll have more stretch of the smooth muscle it's just like if you stretch on a balloon that balloon wants to contract back to its normal normal size again so the smooth muscle cells will contract the vessels will constrict allows less blood into the glomerulus and compensates for a greater systemic blood pressure so if blood pressure is high we want if I have a high blood pressure then we want to create a low um hydrostatic pressure by reducing glomerular blood flow so um blood flow into the glomerulus did I put um oh increases let's put that right here increases blood flow I didn't put that to raise hydrostatic pressure of the glomerulus okay there you go and then again your GFR remain normal and so this is something that is going to happen automatically nobody has to tell anybody what to do anything I don't need a reflex arc to happen I don't need hormonal secretion to happen I don't need anything this is just the little afferent arterial is just is just Contracting and relaxing Contracting relaxing just okay let me show you because this is what I do with my on-campus kids this is what your afferent arterial is doing all day long every day it's just okay you're running up the stairs oh I got a vasoconstrict there's too much stress I got a vasoconstrict I'm laying down I got a vasodilate more blood comes in I'm getting up out of my desk I'm going to vasoconstrict I'm going to sit in my desk I'm going to vasodilate this is what you're this way this is what your afferent arterial is doing all day long every day it's just adjusting because of the amount of blood that's coming into um into the affair and arterial and causing it to stretch okay so just remember your little Pinchy um blood vessel there okay so this picture is going to show you exactly what happened so here is normal systemic blood pressure normal Affair and arterial diameter normal GFR Okay so GFR is normal all right so now what if my blood pressure is too high okay so this is if my systemic blood pressure is too high I would just be shooting oops this is GFR I would just be shooting that filtrate through there and not have enough time to reabsorb so I can't have that happen so what I want to do is vasoconstrict the afferent arterial so notice that it said the narrowed arterial Lumen allows less blood into the glomerulus to offset and increase in systemic blood pressure like we just said okay now here is um uh the other thing that we want to do we want to decrease filtration surface area so notice how the the Glo the capillaries are are just in filling the space of the glomerular capsule in this in this middle situation right here with normal systemic blood pressure if I have high blood pressure what I'm going to do also is contract those mesangial cells so the cells that are in the glomerulus and so it's going to pull in and we're going to read reduce the surface area for filtration um we just tighten up the ball of yarn so that there's less pieces of yarn where the blood can come or the filtrate can come out okay and then and then we just usually just leave the efferent arterial alone okay so um so that's what we're going to do if my systemic blood pressure is too high if my systemic blood pressure is too low then my GFR is too low so this would be in the case of high High GFR okay so what I want to do to lower it here is if I have too low of GFR I'm not filtering enough I'm not getting rid of the wastes like I should so I'm going to vasodilate and the widened arterial Lumen allows more blood into the glomerulus to set off a decrease in systemic blood pressure then I'm going to relax the mesangial cells and then that will allow more surface area for filtration and I will increase my GFR okay so number one thing we're going to do and it's going to be doing it all day long every day constantly because your your systemic blood pressure is always changing and so your myogenic response will always be active all right now what about tubular glomerular feedback okay so what we're going to do is this is a um backup to the myogenic mechanism in response to increased blood pressure okay or decrease blood pressure either one okay well I'm going to put the decrease one in here too because they don't have that I don't know why okay so if glomerular blood pressure is increased so what we're going to see is more sodium chloride in the tubular fluid that will be detected by the macula densa cells and so they will release a vasoconstrictor so the macula densa will signal oh I don't know why this doesn't have the decrease well I'll write it all in for you make sure that you put this in your notes because you need to know the decreased one as well so the macula densa will um further basal constrict the afferent arterial let's go to we're gonna have to go way back I'm sorry I need to put um this picture in there wow I'm Gonna Let You Down jeez friends okay oh my gosh so this is who's gonna be working is my juxtaglomerular apparatus and so this is who's going to be um working with tubulo will marry your feedback well veruler feedback okay so what's gonna happen is that my in I have an increase in uh systemic blood pressure so I've got a lot of blood coming in here and my GFR is too high so GFR too high uh so how am I gonna know besides the fact that if the stretch is too much so I'm going to push out on here and then my smooth muscle cells in here are just gonna um contract and I'm gonna vasoconstrict but maybe that's not enough maybe my GFR is too still too high how am I going to know that well my macula densa right here so these cells right here as I've said before are chemo receptors all right so these are like um back in the 70s or 80s when I was growing up they probably in the 70s they had this commercial on for Fruit of the Loom underwear and um they always had in the package a little slip that said inspect um something approved by inspector 21. so there was this inspector this quality assurance inspector that had checked all of the Fruit of the Loom underwear and so we always wanted to know who inspector 21 is and so that was always kind of like a running gag in the commercials um so yeah once you once you have finished your product we still have to check it for Quality so we still have to have somebody at the end of the conveyor belt making sure that the underwear you just made was right or if we go back to the I Love Lucy and the Drake and Josh examples that I used we want to check the box of chocolates or we want to watch check the container of sushi and we want to make sure are they placed in there properly do I have the right number if the conveyor belt's going too fast maybe I don't have enough um uh chocolates in my box and if the conveyor belts going too slow I'm not making enough box of chocolates boxes of chocolates so that's the job of my macula densa so it is an inspector because we're at the end of where we're absorbing from so we've already absorbed everything we're going to absorb from the distal convoluted I mean the proximal convoluted tubule and the loop of henle so now we've come to the distal convoluted tubule this is the only spot I have left the only place I have left to fix what's wrong to make sure that my filtrate is produced at 125 milliliters per minute with the right concentration so my macula densa cells check they inspect to see what the sodium chloride content is so if the GFR is too high I will have a high sodium chloride content because what happened was I didn't get to reabsorb it like I should so what am I going to do I'm going to vasoconstrict so I'm going to send a vasoconstrictor to the afferent arterial to the afferent arterial so that's what I'm going to do if my blood pressure is too high my systemic blood pressure is too high now what am I going to do if the systemic blood pressure is too low so I need two get rid of all of that so now I just have a little bit going in here because I'm laying down or whatever I'm doing so now there isn't stretch on the walls so my um uh my afferent arterial is going to dilate so let's see um GFR too slow then how am I going to know my macula densa is going to look and see I have two little sodium chloride in here which means I'm not filtering enough not filtering enough and so then what am I going to do well I'm going to stop I'm not going to secrete a vasoconstrictor so no vasoconstrictor and instead I'm going to stimulate my granular cells to release renin we get into the renin angio mechanism and Angiotensin mechanism in the next video then we'll talk all about how do we correct that when our GFR is too slow because of low systemic blood pressure okay so let's go back to that slide which I really apologize that should have been right there all right Okay so if um lumerular blood pressure decreased then the amount of sodium chloride in tube you will fluid also decreases and then so again we'll detect detected by macular densa and we will stimulate JG or granular cells to release renin okay and so we'll get into that in just a little bit all right now how effective oh let's go back here one more thing all right so if um if glomerular blood pressure is increased we're going to get a GFR of greater than about 140 milliliters per minute that's when we're that's when our macula dense is going to go oh hey you got too much sodium chloride in here and we gotta shut things down okay now what about if glomerular blood pressure is decreased then my GFR is going to fall below 90. milliliters per minute and that's when I need to kick in and do something about it so there's a range um at which my um autoregulatory mechanisms work real good so my myogenic mechanism and my tubular feedback are gonna kick in at a range between 80 and 180 millimeters of mercury this is systemic blood pressure okay so if my systemic blood pressure is between 80 and 180 ML meters per Mark millimeters of mercury then I'm gonna do auto regulation but what if my body so what if my systemic blood pressure drops below 80. so um I'm hypotensive for whatever reason I'm hypotensive okay I'm going to maximally dilate my materials okay to try to raise it but there will be a decrease in blood glomerular blood pressure and GFR and if it's really low I just won't even eliminate waste in the urine because I'm not going to filter no filtering and there's a reason why we want to do that and we'll get into that when we talk about um if our systemic blood pressure is less than 80 what's our body going to do about that extrinsically now if my blood pressure is a bit of 180 what I got to do is just shut down those arterials as much as I can maximal constriction going on and I will still get an increase in glomerular blood pressure and GFR and too much urine form so I will lose water and sodium chloride and I don't want that okay so I've got to shut things down outside of my body so like um like I said if you are between 80 and 180 Auto regulatory mechanisms will manage your urine production if I have a blood pressure lower than 80 systemic blood pressure lower 80 lower than 80 I won't make enough urine and if my blood pressure is higher then I'll have too much urine and that can be problematic if we let that go on for too long so how do I do that what am I going to do in this range right here and then what I'm going to do in this range right here so that's what we're going to take a look at right now okay um oh and then one other thing um which one of these do you think you're more in do you think you're in a situation where your blood pressure is too high or your blood pressure is too low so think about that answer it out loud to yourself and then let's see if you're right so let's think about what are you in which division of the ANS are you in most of the time are you sympathetic or are you parasympathetic if you said parasympathetic and you said that your blood pressure was usually low on the low end you are right so what does that mean well if we go back to when we were talking about blood pressure okay blood pressure is equal to cardiac output times peripheral resistance well if parasympathetic is acting on cardiac output what do we know cardiac output is going to do it's going to do that and if sympathetic is not acting we are going to dilate let's not put dilate we're going to put less vasoconstriction right because if your non-insympathetic stimulation you don't have that epinephrine and that more norepinephrine traveling through your body that's going to bind to those Alpha One adrenergic receptors and cause vasoconstriction in your vascular smooth muscle right so I'm going to get less of that so this will be down and this will be down so most of your day you're going to spend more in a too low blood pressure situation um unless your chronic hypertensive so this would be chronic hypertension usually We're Not Gonna this is not too bad of a problem but this is this can be a problem as I say can be problematic so what are we going to do about it well let's see so now we're going to use nervous system and hormonal control so these are extrinsic controls these are going to affect these affect the whole body as well as the kidney so I'm going to be working on other things as well not just acting on the kidney now I will be acting on the kidney but other things will be happening as well so um extrinsic controls our physiological processes to change GFR so we're going to try to really bring it up from where we were before less than 90 um even way less than 90 or to bring it way down from 140 or 150 milliliters per minute Auto regulation is just maintaining that GFR between 80 and 180 milliliters oops milliliters no milligrams per oh my heavens millimeters of mercury sorry friends it's late I'm tired all right so let's say that [Music] um I have um what am I gonna do I if I'm exercising what's my blood pressure gonna be it's high so how do I decrease my GFR if my if I'm in sympathetic stimulation okay so this is going to happen during exercise or emergency so what I want to do is shut off urine production because if I'm exercising and I'm making lots of urine then I'm going to lose lots of water I'm already probably losing a lot of water through sweat anyway so I need to um slow down urine production so I want to decrease urine production if I'm in sympathetic stimulation all right so what am I going to do I am going to decrease my GFR through vasoconstriction of the affairnin efferent arterial so I'm reducing the blood that's entering the glomerulus now sympathetic stimulation also um so these guys oh which ones do they have um I'm gonna pause this while I while I look really quick oh no that's the wrong thing hang on I gotta stop doing this okay I'm pausing my recording really and I'm back okay so it was made at once just like in your heart okay so beta ones let's go back to my picture I just didn't want to tell you wrong all right so um what's gonna happen is that uh beta 1 whoops okay whoopsie sorry about that okay so beta 1 adrenergic receptors on the JG cells will release renin which is going to result in Angiotensin II production and contractions essential cells so we'll get less filtration surface area and we're going to get vasoconstriction so we're trying to preserve what fluid that we have and then oh like there are contractions of essential cells decreases surface cervical mirrorless decreasing the GFR body therefore conserves water under stressful conditions okay but we're also going to to um increase our blood pressure okay so in a little bit we're going to turn this around and we're going to look at how do we increase systemic blood pressure also through the release of renin so okay so here we are stressor emergency sympathetic sympathetic stimulation of kidneys we're going to get both basal constriction of the afferent arterial and then we're going to get the release of renin by the JG cells and then we're going to get Angiotensin II and we're going to get contraction of the mesangel cells and then the result down here so we have vasoconstriction the afferent arterial decreased blood flow decreased filtration surface area through the contraction substantial cells decrease GFR decreased filtrate basal constriction the affin arterial decreases blood flow and contraction resangial cells decreases filtration surface area GFR decreased filtrate decrease more fluid retained in the blood which maintains blood volume now this is going to be a stress or an emergency so maybe I'm going to have low blood pressure um or excessive fluid loss or excessive fluid loss or shock because I'm going into sympathetic stimulation okay then we can increase GFR because I if I um well through atrial natural peptide all right so remember A and P is the hormone that's released from your cardiac muscle cells in the Atria when your Atria get too stretched because your Atria just do not like to be stretched because this is too much blood volume so what we want to do is get rid of plasma so we want to get rid of water so how are we going to do that and what else what kinds of things do we need to activate to increase that so if we're going to relax the afferent arterial we're going to increase hydrostatic pressure and we're going to increase net filtration pressure whoops that filtration pressure which will increase GFR so now I'm filtering faster I'm going to inhibit the release of renin okay because that's going to contract my mesangel cells and that's going to cause ultimately cause vasoconstriction I don't want that so I'm going to relax my mesangel cells which is going to increase my filtration membrane surface area allowing a greater GFR and now if I have a greater GFR I'm going to make more urine volume which is going to decrease blood volume and decrease blood pressure because that's the goal of what we want to do with A and P one decrease blood pressure because you know what your heart's like that's too much blood coming in there I don't like this and so here is what's happening um there so um increase GFR through A and P increased blood pressure volume atrial wall stretches and P released and then we'll get both vasodilation of the afferent arterial and relaxation cells and then vasodilation increases blood flow and more filtration and increased GFR infiltrate increased and more fluid eliminated in the urine all right so um I'm gonna skip we're going to pause here for a minute and then um uh and then I'll be back in a minute okay well it looks like you're off the hook because I have the rest of um glomerular filtration let me get rid of me go back to my screen sharing um the rest of GFR maintenance that we're going to do whoops that we're going to do we're actually oops gonna do in the um water and electrolyte balance section of this and when we talk about more of what Angiotensin 2 does so we're going to leave this video right here and the next video will begin with the reabsorption and secretion of material so how do we transport material into and out of the Nephron so that's all for this video