 Hello everyone my name is Dr. Kamal and today I'm going to be breaking down cardio for you. Cardio is one of the most high yield subjects on the exam being the number one killer in the United States is cardiovascular disease. So I know a lot of students have difficulty with cardio. My aim is to basically break it down and make it easier to understand. So if you can have a greater understanding of what the heart is doing through the different cardiac cycles then this will make the questions easier to answer. So when it comes to the heart a sort of frame of reference you want to use is the cardiac cycle. So the cardiac cycle helps shows us what's going on when it comes to pressures involved in the heart and also what happens when it comes to opening and closing of the valves. So to break down the opening and closing of the valves we do have a very good mnemonic called Coco-Mam. So basically it's close open close open and then mitral aortic aortic and then mitral again. So what happens is your heart works almost like an engine in which it needs to open certain valves and close certain valves to help promote the blood to get officially in the heart and out of the heart into the body. So when it comes to understanding the cardiac cycle you always want to start with S1 because S1 is the first heart sound and it's the start of systole which is you know the systolic ejection phase. So we want to start with S1 so when it comes to the Coco-Mam this corresponds to the close. So S1 starts with mitral closing. So now we have the isovolumetric contraction phase. So this means isovolumetric. So the volume isn't changing so we have the volume here at the bottom of the graph. So the volume isn't changing but the heart is contracting. So the heart is basically contracting up to build enough pressure for it to overcome the pressure in the aorta. So in this makes sense the way the blood leaves the heart is it leaves the left ventricle, the aortic valve opens and then blood gets pushed from the left ventricle into the aorta. But the pressure that the heart needs to overcome is the pressure in the aorta itself. So if you can imagine our resting sort of mean arterial pressure if systolic is 120 and diastolic is 80 it has to be at least greater than that for blood to actually leave in the heart leave the heart because otherwise if we open the aortic valve instead of blood going from the left ventricle blood is actually going to go left ventricle into the aorta it's actually going to go from the aorta into the left ventricle. So we want always blood to go forward flowing and out of the heart. So the way the heart is going to do this is it's going to go through isovolumetric contraction and then at the point where the pressure is actually greater than the aortic pressure than the aortic valve will open. So that's what we see here. So this is labeled A so as in the aortic and now it will open. So always think MAAM, COCO. So COCO. So now the aortic valve opens and the aortic valve opens allowing that blood from the left ventricle to get into the aorta. So now we have a phase called systolic ejection. So now that the aortic valve is open now the blood can leave the heart and get into the heart of the aorta. So this is called the systolic ejection for a phase. So once you know the left ventricle has done its thing it's sort of pumped out most of the blood. Now we get the aortic valve that actually closes. So remember our mnemonic close open close open MAAM. So now the aortic valve is going to close. So now this is basically signifies the end of systolic. So now the heart basically starts relaxing. So we call this isovolumetric relaxation. So again isovolumetric the volume isn't changing and the heart is relaxing. So all of that muscle that you know contracted in the left ventricle is now relaxing so in order to get ready for filling. So the pressure is dropping rather quickly. So now we have we've finished our isovolumetric relaxation and now we get into our filling phase. So now the mitral again is going to open. So in order for blood to get into the left ventricle the mitral valve has to be open because remember the mitral valve is what connects the left atrium to the left ventricle. So in order for the left ventricle to fill up and get ready for another systolic ejection phase we need that mitral to open up. So the mitral will open and then the left atrium will contract and push all the blood into the left ventricle and fill it up so that now the left ventricle can again push the blood out. So that's what's signified here. So we have our mitral that is opening and that's indicating that this is the filling phase. So this is where we also see our S3 and S4 sounds. So remember the S1 and S2 are the normal heart sounds and then S3 and S4 we'll talk about in a later video as well but these are the sounds that are more associated with pathology of the heart. They can be normal in certain situations especially S3 can be seen in children and pregnant females but more of we do want to sort of associate this with some sort of investigation. We need to see why then we're having an S3 and S4. So S4 we can also see in left ventricular hypertrophy. So that's an overview of the cardiac cycle. We would definitely like you to share this video also like it subscribe to the channel. We're regularly adding additional medical questions content and then you can also use a special promo code right below and that will give you a discount as well.