CARDIAC CYCLE Explained

CARDIAC CYCLE Explained


Alright guys, so let see whether I can explain this within five minutes so I’m going to explain about the cardiac cycle which involves the left side of the heart specifically the left ventricle left atrium and also aorta so.. basically there are four main phases of cardiac cycle ventricular filling isovolumetric contraction ventricular ejection and isovolumetric relaxation like I said, cardiac cycle, involve the left ventricle so there are two main parameters that I’m going to explain here the first one is the pressure which involve the intra atrial pressure intraventricular pressure and also intra aortic pressure as well as the intraventricular volume in ml so I’ve divided this graph into spaces which represents its own cardiac phases the ventricular filling, the isovolumetric contraction ejection and also isovolumetric relaxation and the filling again and then the space here represent the ventricular diastole followed by systole and followed by diastole. remember this is the ventricular diastole and systole and the small area before the ventricular systole is actually, the atrial systole alright. so.. I explain the left ventricular volume change first the maximum I put here is 120 and the lowest it can go is 50 so if you minus 120 minus 50 is actually you get the stroke volume which is 70 mls alright. so during ventricular filling there is a slow rise in the left ventricular volume and then during the atrial systole a lot of a.. much of the blood inside the left atrium is pushed into the left ventricle so there is a peak high and then during the isovolumetric contraction as the name suggest isovolumetric means the left ventricular volume remains the same and then during the ejection, most of the blood in the left ventricle is pushed outside from the ventricle so the volume will be reduced and this remains the same until the end of the isovolumetric relaxation and then during the ventricular filling it starts to rise again that’s it about the left ventricular volume let’s explain about the change in pressure for the left atrium first so I marked here 10mmHg up to 120 mmgHg so for the left atrium during the ventricular filling, there is flling of blood inside the left atrium as well. so together, there is a slight raise in the left atrium until during the atrial systole where the pressure rises and then during the isovolumetric contraction there is a drop in pressure but there is a slight notch here the notch here because of the closure of the mitral valve so, that’s why there’s a slight rise in the left atrial pressure and then during the ventricular ejection so what happen in the left atrium is actually there’s filling of blood because after the atrial systole, the atrial starts to relax during this atrial relaxation, which coincide with the ventricular ejection the blood starts filling the left atrium so the pressure slowly rises alright. until the left mitral valve open where the pressure drops and during ventricular filling as the earlier suggest it coincide with the atrial filling the pressure slowly rises alright. let’s see what happen to the pressure change in the left ventricle so, it follows the left atrial pressure initially but as you can see the left ventricular pressure is slightly lower than left atrial pressure this is made possible because the blood has to flow from the left atrium to the left ventricle so there must be a different in pressure means that the pressure in the left atrium must be slightly higher than the left ventricle so that the blood will flow from the left atrium to the left ventricle otherwise it will flow the other way round and then during the atrial systole, there’s a because the blood is pushed into the left ventricle so the pressure rises slightly and then during the isovolumetric contraction the volume remain the same but the pressure inside the left ventricle markedly rise until during the ejection the pressure is increased to maximum upto 120mmHg and start to fall down during the isovolumetric relaxation and then it follows the pressure in the left atrium and let see what happen to the pressure inside the aorta the aorta…. as you can see the aorta is outside the heart the pressure is actually reflects our blood pressure so during diastole the pressure should be arround the diastolic blood pressure which is arround 80mmHg and then it starts drop until the ventricle starts to eject out the blood when the ventricle eject out the blood so this blood goes into the aorta and the pressure inside the aorta raised markedly untill it reach the systolic blood pressure and then start to drop down untill during isovolumetric relaxation and then there’s a slight notch here this notch is because of closure of the left aortic valve during isovolumetric relaxation the blood starts to flow backward towards the heart during that time the aortic valves close because of this closure there’s slight backflow in the aorta itself so this raised the pressure slightly so you can see a notch here and then the pressure in the aorta drop slowly until it reach the diastole alright guys.. that’s all about it thanks