finally folks we are at my favorite part of the cardiovascular Network lectures talking about the control of blood flow out to the system now I know you probably think we've talked about that plenty but we really haven't we've talked about arteries and veins capillaries their structures how fluid movement may be able to take take place across their membranes or not but now we need to understand how do arteries know to bring more fluid over to a particular capillary good how does a capillary bed let arteries and veins know we're overflowing here we need to move fluid away from here there is a set of governing bodies or areas that control this blood flow and we need to discuss those we're going to start as you can see here from the slide we have two parts of this we're going to start with part one try to get us oriented with some things and then we'll move into the second part and and hopefully give you a better understanding of how blood flow is controlled around the body let's get started if we're going to talk about control of blood flow around the body you need to understand that our cardiovascular network works in many ways like I guess you could say our our political system we have local control or we have local politicians and in governing individuals who are supposed to be taking care of just what's happening in our area just what's happening here on this campus if you if we can talk about the college itself and then we have folks that are overseeing them at on a larger scale I guess you could say so we have City officials then we have govern uh State officials that are looking over certain aspects and then we have national uh leaders that are trying to all govern and take care of the system and at each one of these levels there is a particular um job that each one is supposed to be handling all right and focusing on the same thing with the cardiovascular Network and so how again do capillaries let the arteries and veins know we need more fluid or we need less fluid there is a two-way conversation kind of going on here and yes you'll see at the end there is a specific uh job overall that it's trying to take care of and we'll get to that when we get to the end of these lectures so let's get started with talking about this control of blood flow we need to first talk about what's called local control and this local control means a very small area small set of capillaries talking to the immediate arterials and arteries that are feeding them the nutrition or the fluids the nutrients the oxygen that that particular area may need or that particular very small area may need so yes our capillaries can actually talk to the arterials how do they do that well the easiest way to kind of start this this discussion is the scientists have been able to see that these capillaries and the cells around those capillaries will literally send messages to the arterials to dilate or constrict altering fluid movement into particular areas now this local control has a couple of of features to it we have acute control meaning short-term control where particular molecules are released from the cells around a particular area that can activate the smooth muscle cells that are associated with the capillary beds and the arterials in that area this can change fluid movement in an area dramatically I have listed here Sevenfold changes that can actually occur we also have what's called long-term control meaning it's not just for what's happening just in that moment but if this continues to happen should we kind of change the overall plan here that's what long-term control about is about and so another set of molecules being released that will also that will alter I guess you could say the development of a particular tissue so think about you and your muscles working out that if you continue to work out those muscles time and time again we should probably increase blood flow to that area while increasing blood flow just by changing the diameter of some of the vessels may not be enough we may need to make more vessels angiogenesis and so some of this long-term control requires building more pipes out to those tissues to bring more oxygen to that area so acute or short term types of changes and long-term types of changes now we also may have particular bits of information coming from other parts of the body so that means local control well probably it should probably be superseded by something from some other group saying guess what there's a huge amount of material coming down and we need we need to make sure that you guys are ready well that's where we jump into control by particular hormones these hormones and in some cases neurotransmitters will be acting as kind of of signals from other parts of the body to tell a local group of vessels you're going to have to alter yourself you're going to have to change everybody got that okay well let's let's focus first on local control and some of the features that may be associated with local control one aspect of all of this that it seems to be pretty clear is that capillary beds are very very sensitive to concentrations of oxygen and this probably makes sense to you if we are requiring oxygen for oxidative phosphorylation let's say in muscle tissue making sure that we have enough oxygen in a particular area is very important very very important so being sensitive to low O2 levels is a big feature we have a couple of ways that the actual capillary networks kind of manage this one of them is called the vasodilator Theory with the vasodilator Theory one of the products that sells in a particular area May secrete or increase in concentration is adenosine adenosine now you should know what adenosine is especially its relationship to ATP adenosine triphosphate if tissues in a particular area of the body are working hard working extra hard they're going to be using a huge amount of ATP meaning breaking it down from ATP to ADP when you do that you start to free up or you make you generating a larger concentration of free adenosine well that free adenosine that is released or is sitting in that tissue signals smooth muscle cells that are associated with small capillary beds and arterials to dilate meaning there's a lot of activity going on we need to increase blood flow to this particular area and that's the signal adenosine bring in more oxygen bring in more ATP now we can take care of whatever we're doing again this is more of an acute type of Regulation there's also this Con this situation where actual smooth muscle cells that are forming some of these little sphincters and ringlets around the arterioles well they need oxygen too so if a tissue is really active and it's using up all the oxygen that means these little smooth muscle ringlets that are sitting around arterioles are not going to have oxygen to initiate contraction or to keep contraction going which means they're going to eventually just dilate they're going to go flaccid when they go flaccid that's going to open up a blood vessel allowing more fluid to come in bringing more oxygen we start to contract again in this image this is a capillary kind of network or a small capillary Network and this vessel appear along the top here we're going to label it a met arterial or a small arterial and there's those smooth muscle ringlets that we talked about in a previous lecture and those smooth muscle ringlets I told you were kind of strategically placed so that well if this one's constricting it's going to prevent fluid from moving in this direction force it going in another Direction well these structures here that look like fried eggs well these are actually cells in the area if these cells are working very hard and using up all the oxygen in a particular area well that smooth muscle ringlet it needs oxygen for its contraction process if it doesn't have oxygen that means it's not going to be able to contract it's going to dilate relax fluid is going to move into the area bringing oxygen oxygen comes out to the tissue so they they can be used and the oxygen can be used by the sphincter well that means it's going to constrict as soon as it gets some oxygen itself regulating I don't have enough oxygen more fluid comes in I have enough oxygen I'm going to constrict a little bit and regulate It Off does that make sense folks so these little ringlets are sensitive to oxygen sensitive to oxygen concentrations that make sense another way to kind of illustrate this is in this little diagram here and this first one up here at the top hopefully this is an arterial first of all this is a capillary these are the tissue cells in this in this particular area blood flow to these capillaries is going to provide them with a enough material so that that can be exchanged into the intracellular space here the cells can use what they need they can use the oxygen which is here in purple the green is CO2 given off by the cells if the cells are working in a normal capacity this exchange is pretty equal we're bringing in enough oxygen and we're taking away the CO2 everything is happy however if these cells start to work overtime they're going to be burning up more oxygen as they burn up more oxygen that increases the amount of CO2 in the area that's CO2 level increasing signals the arterial the muscle cells associated with the arterial that we need to we need to change things those muscle cells will actually dilate blood flow increases coming into coming through that arterial into the capillaries bring more oxygen get rid of CO2 we've regulate it this is a local control a local regulation of CO2 and oxygen signaling the vessels so that we can bring this material to these cells in this image we have kind of a flow chart to show you just what we were talking about a few minutes ago so if we start up here metabolic rate if it increases metabolic rate meaning those cells are working harder they're going to increase the amount of o2 that they use if they increase the amount of o2 the amount of o2 in the tissue is going to drop is going to drop smooth muscle cells are very sensitive to that if O2 level drops they relax causing vasodilation meaning the resistance is down meaning more blood flow is going to increase into that area as blood flow increases O2 is delivered to the area tissue concentration of o2 increases and that feeds back onto the system to alter those smooth muscle cells and alter the system itself regulating itself regulating does that make sense folks good good let's move over to one other component here let's look at high blood pressure high blood pressure okay now I'll let you know folks our bodies are not necessarily used to dealing with high pressures over our Evolution our body's biggest problem has been low pressure remember I told you we're a big water balloon I sent this way back when and our body is looking to maintain fluid volume remember when we talked started talking about the cardiovascular Network maintaining volume well again as we've evolved our biggest problem is leaking getting punctured our skin getting punctured sweating all that losing fluids we have multiple mechanisms to try to take care of low pressure low volumes high pressure we don't have a lot of mechanisms do we have some yes and so let's talk about a couple of those here these shouldn't make sense to you because we're going to plan a theme that we just we just talked about here a few minutes ago with high blood pressure we're going to look at what's called the oxygen demand Theory metabolic oxygen demand Theory what does this mean well high blood pressure brings in excess oxygen make sense brings in a lot of fluid to a particular because it's being forced because of a high blood pressure which caught which will cause contraction of that capillary bed smooth muscle causing constriction to put you know of these to the tissues that means it's trying to regulate them protect those vessels remember I said capillaries can't deal with high pressure so in a way this is a protective mechanism unfortunately high blood pressure mechanisms like this well if we cause those capillary smooth muscle ringlets to constrict to protect the capillaries that means pressure or fluid is going to back up in the larger vessels and that's going to cause pressure to go even higher bad sign for us not a great mechanism in our body but it's something that our body has had to try to try to put together you know on the short term on the short term there's another theory called the myogenic theory the myogenic theory and this you also know a little bit about do you remember us talking about the alignment of actin and myosin filaments the myogenic theory the stretch of the capillary smooth muscle when they get stretched that puts them in a better actin and myosin alignment it causes them to be able when they do contract to come track back with greater force causing basil constricted causing vasoconstriction so with this myogenic response again if we start up here in the corner perfusion pressure or the amount of blood coming into an area increases stretch of arterial smooth muscle we're going to get a greater constriction greater resistance and we reduce flow reduce flow well that's going to be that's going to be kind of altered here by this increased flow of fluid trying to get in it's finally going to start to back up at some point decreased perfusion into a particular area no contraction because the smooth muscle roulets don't have oxygen constriction drops off resistant to increase the flow we have a way of kind of controlling it so you can see this should be working in two directions unfortunately because of other high pressure mechanisms it doesn't work very very well CO2 we've talked about before as well in these two flow charts here and I like using flowchart for many years because it's linear for the most part you can see how things are kind of working up here again metabolic rate increases we increase CO2 production CO2 production causes smooth muscle ringlets to actually dilate to actually dilate they will dilate resistances down increase blood flow increase removal of CO2 tissue concentrations of CO2 drop that's the feedback and that this should self-regulate this should self-regulate over here blood flow blood flow into a particular area drops off CO2 concentrations increase and we have the process all over again all over again now folks I need you to go over these mechanisms here and bring them up in lab let's talk about them this is going to be very very important to you and it will be on the midterm so let's talk see you soon