hi this is dr. cat fleece at central New Mexico Community College we continue our discussion on heart physiology with video K which focuses on the graph that compares the different pressures in different parts of the heart even the aorta volumes heart sounds and even EKG let's start by focusing on this image that comes out of your book and that's a an image that doesn't have as as much detail on it as the next image whenever we see this kind of these kinds of graphs combined bear in mind that we're really focusing on the left chambers of the heart in other words the thick left ventricle with its left atrium the right side of the heart would not have us pronounced a graphs as we see here let's start by identifying what each graph represents as well as the axes so on the y-axis here we have pressure in millimeters of mercury and then we have in the orange here the pressure in the left atrium in the green here we see the drastic change in pressure of our left ventricle and here in the red we see the change in pressure in the aorta of course if this were the right side of the heart this blood vessel would have to be the pulmonary trunk and the pulmonary arteries near the bottom were also showing heart sounds with the first heart sound or the love followed by the second heart sound or the death let's just ignore this third heart sound that your book added I don't see any reason for us to discuss that well if we know where our love and duct occur then we already know where our a V valves closed and where our semilunar valves closed because the love represents the closing of the AV valves and the dub represents the closing of this semilunar valves so that's re one thing for us to point out the other thing to remind ourselves off is that blood will always follow it's pressure gradient and if the pressure in between two chambers are between a chamber and an artery are the same our blood is not going anywhere so let's start at this point in the graph this is where the atria are and the ventricles are beginning to collect some blood the heart is completely relaxed and blood is trickling into the chambers and then we see right here a bit of a bump in the pressure of the atrium which is when the atria or atrium contracts and squeezes the blood into the ventricle and that makes sense then that we right here see that the AV valves closed because as the blood begins to fill up the ventricles the blood pushes up against the AV valves closing them this is also then the time period when the ventricles start to build up pressure in their ventricular systole as we see here and the pressure continues to rise and continues to rise and now the pressure is equal to the pressure in the aorta but then the pressure in the ventricles exceeds that of the aorta and that is what allows the blood to enter into the aorta and open the semilunar valves I should have said it allows the blood to open the semilunar valves such that it can enter the aorta and as blood enters the aorta we're going to see a bit of a rise of pressure in that a Horta just a mere presence of that blood gives it a rise in its own pressure but once the Blood starts to flow into the aorta the pressure begins to drop somewhat but especially since the pressure within the ventricles begins to drop and here we see that the pressure within the ventricles is now lower than that in the aorta and the blood is literally going to flow backwards in that a aorta pushing against the semilunar valves closing them so right about here where the pressures are about equal the valves will close the semilunar valves as the blood bumps up against the valves we're going to see that it creates a slight pressure for a short period in the aorta creating a little bump and the knot just before that bump we often refer to as the dicrotic notch we saw that term spelled out on a previous slide so the dicrotic notch is the little dip in the pressure of the aorta as the blood literally slams up against the semilunar valves that have just closed so we see a bump here which is the rising pressure which was preceded by a bit of a dip as we see the the pressure of the blood dropping now as the pressure continues to drop in the ventricles eventually the pressure in the ventricles will be the same as in the atria and therefore the AV valves will easily open and blood will begin to trickle into both the atria and the ventricles so it's important for you to recognize where the valves closed which is easy if you have the heart sounds showing here but you also need to figure out when the valves open and for that you need to have an idea or you need to be able to interpret the graphs as when the graph of the atrium crosses that of the ventricles we're going to ultimately see that one of the graphs is going to increase in pressure which therefore gives us an indication of where the blood is going we see that in particular here where the pressure of the ventricle continues to rise it exceeds that of the aorta such that the semilunar valves open and the blood is ejected as the ventricles relax eventually the pressure in the ventricles is so low that the semilunar valves will close as the blood flow back flows backwards in the aorta and that creates this little bump here in the pressure of the aorta where the blood literally hits the valves and so that slightly elevated bump or slightly elevated pressure is preceded by a little notch we call the dicrotic notch here we see a graph that's even more informative does this from Wikipedia and you can see the reference listed here near the bottom left there are also several videos on my playlist that discussed this particular graph you can once again see our heart sounds here again don't worry too much about the third heart sound just focus on the first and second heart sound but we also see the EKG shown here so we're relating the EKG to the closing and opening of the valves as well as the different phases of the cardiac cycle depending on where the blood is going we've also added a volume graph here which illustrates the rise and fall in the amount of blood in the ventricles and of course if the pressure in our ventricles which is in the blue here is high you would expect for the volume of blood to be low right if the pressure is highest that's when most of the blood is ejected into the aorta we're going to end up with the least amount of blood in the heart okay so this top graph should look quite familiar we have in the blue we have the ventricular pressure the gray bottom line is the pressure in the atrium and then we also have the change in pressure in the aorta you can even see our dicrotic notch here etc etc one thing that's been added here is the detailed phases of the cardiac cycle including systole and diastole and systole for instance down here but notice especially our isovolumetric phases as well as the ejection phase so let's see if it makes sense where these phases have been added remember I saw volumetric and here they call it isovolumic phases either way are the phases where all valves are closed and and it's a very brief face the isovolumetric phase is going to volumetric contraction phase is going to have to occur right before we see ejection of the blood into the aorta so right here is where the pressure of the ventricle equals the pressure of the aorta the blood is not quite moving yet but when the pressure in the ventricle starts to rise you can expect or you can assume that blood is entering the aorta which is why we see the rise in the pressure of the aorta so this we refer to as the ejection phase with phase which continues until the pressure of the ventricle and the aorta are equal again after that we're going to see the very brief isovolumetric relaxation phase each one of these isovolumetric phases whether it's the ice volumetric contraction phase or the isovolumetric relaxation phase is going to stop the moment any valve opens because isovolumetric phases are defined by the closing of all four valves so right here we see the opening of the aortic valve and that indicates the end of our isovolumetric contraction which makes sense because here we see that blood is ejected into the aorta because of the pressure changes that are occurring on the other hand here we see the opening of the AV valves which tells us that that must be the end of the ISO volumetric relaxation phase which is this brief period here during which we've which starts with the pressure of the ventricle being equal to the pressure of the aorta and after which the ventricular pressure continues to decrease to continues to decreased until it gets so low that it's equal to the pressure of the atrium and that allows for the AV valves to open so the two isovolumetric phases are quite short now we learn to relate the heart sounds to this pretty complex diagram I didn't talk much about the volume except for pointing out that the volume is going to have an opposite or I should say there's going to be less volume and the ventricles when the pressure is high and vice versa but let's take a look now at the EKG and let's focus for a moment on the QRS complex let's say the QRS complex during that time our ventricles depolarize and so what halfway we should see that they begin to contract and dete if we start someone halfway throughout the QRS complex notice here that our ventricles must be contracting as the pressure change indicates and at the same time briefly after contraction begins to occur we should see that the volume of blood in the heart begins to drop indicating that it's leaving the heart so you can also relate the EKG to the pressure grafts as well as the volume graph so be sure your practice with all of this so this wraps up our discussion of the cardiac cycle heart sounds EKG we're ready now to move on to cardio dynamics