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Kinesiology & Health Science
KINE 3012
Gillian Wu

Feb 27 , 2012 Lecture Monday Risks associated with high intensity excericse Periodic elevation in systolic mean arterial pressure that occurs with a single repetition of high intensity excericse -Valvsalva Maneuore pressure is directly transferred to the arteries iwthin the thorax. Risk Factors associated --See the posted images on moodle. Immiediate risk, Catatrophic failure refer to as aneurysms (the wall of the artery rupture) Pic on the left shows the ripped aorta. Blood penetrates wall of aorta. Wall becomes stretch out and becomes weaker since the blood has penetrated in it.No longer strucutural strong, therefore aorta balloons out, the weaker the wall becomes and it can lead to RUPTURE. This rupture is deadly, since this is aorta. Aneurysm of aorta (not likely to occur in young individuals, unless genetic predispotion of having no stronger aortic walls (Marfan Syndrome: which is genetic defect in one of the protein that helps build elastin and lamale(encircle the aorta. Without the protein aorta will most likely to rupture since its not very strong. One of the location of Aneurysm more commin in aged individuals is in the abdoiminal region of Aorta . More common to occur when u get older over 60 , mostly in males than females. It comes down to having disruption in the structure of and disregulation in the amount of elastin that is being distrubted throughout the wall of produced. You can having nothing produced or too much being degraded(protelysed) That leaves wall of aorta much more susceptible to having tears. If you start to develop aneyruym like this , first treatment is done with the blood pressure (meaning its reduced). They wait to see if the wall can be repaired itself in low pressure. Another risk is 1. Myocardial Infarction (Heart attack) Left ventricle has to work against the pressure in the aorta, in order to achieve stroke volume. LV has to create pressure that exceeds aortic pressure in order to have blood being ejected. If you’re MAP, is really high 200mmHg, that means LV has to exceed 200mmHg if it’s going to eject blood. LV can do it if it contracts much more vigioursouly, much more intense contraction, myocardial cells will use more oxygen in order to generate ATP, that’s needed to sustain the actin-myosin cross bridging. If LV does meet higher pressure demand the myocardial cells will need more oxygen to keep doing this, but if it doesn’t that means we WOULD NOT HAVE STROKE VOLUME, SINCE THERE WILL BE NO PRESSURE GRADIENT and BLOOD WILL REMAIN IN THE LEFT VENTRICLE ( we will have much reduced CARDIC OUTPUT (CO) And as a result of Less CO , the myocardial cells will receive much more oxygen. Where does the oxygen come from that feeds the myocardial cells? It’s not coming from the blood that is sitting inside the ventricles, that blood is simply being pumped from one location to another. The only way myocardial cells receiving the nutrients they need is from the CORONARY CIRCULATION (blood vessels that branch of aorta and circle the heart and penetrate through the walls of myocardium to deliver the nutrients and oxygen directly to the myocardial cells) Reducing Cardiac Output you reducing the blood that is going to circulate through the coronary circulation and provide the oxygen to the myocardial cells. So in either situation, either LV is meeting higher pressure but utilizing more oxygen OR you are not meeting the pressure and there is less oxygen being delivered. There is a situation that is likely to occur where the oxygen demand by the myocardial cells is not being met by the oxygen being delivered. If the myocardial cells do not meet the required oxygen that means they will not be able to synthesize enough ATP to maintain their function. The myocardial don’t store ATP they contiously use ATP. Since they are active.. When they can’t synthesize new ATP? Contraction occurs since cross-bridge cycling won’t be able to continue. Other thing is the ability to maintain negative mem potential is lost. Cells become dysfunctional as a result of that and they will not be able to excited. Starred myocytes : not being able to contract anymore *More likely to occur(myocardial infarction) in older individuals than younger people since they are performing high intensity exercises since blood vessels and heart are quite resilient. One other thing that makes it more likely to have heart attack is if you couple the situation where you have very high arterial pressure which your heart is working against , if you couple that with problems in your arteries (problems in the coronary arteries) Most common problem is (coronary artery disease) which leads to formation of atherosclerosis plaques also called atherosclerosis. -Plaque is forming on in the inner surface of the artery -It is the accumulation of both l of lipids, immune cells, smooth muscle cells, collagen. -Plaque can grow and develop into quite a large region within the artery -Structural impediment, small lumen space that has to get blood flowing through it -When you have sever atherosclerosis, blood does not go to the regions that are downstream of the plaque since its very high resistant location to get past. -Less blood is capable of passing down into the smaller blood vessel and exchange oxygen with the heart. -The other risk associated with atherosclerosis, the plaque region down there in the picture can develop Thrombus (platelets are globing on to surface of plaque since they are attracted to the collagen that’s there). --this enlargement could block the entire artery and other potential danger is that the thrombus is not very stable and as blood pushes against it, it is very likely that it could break off and then its going to travel in the blood downstream into smaller blood vessel where it could totally block the blood vessels (embolus is the blockage of smaller blood vessel) If there is no blood getting past this point, and any cells that are downstream of this, are going to be starved of oxygen, real risk that can occur in heart, if it occurs it is going to lead to regions that become oxygen starved that could precipitate a heart attack. Same process occurs in other locations in the body and you can have plaques and thrombus forming in carteoid artery and if those thrombus break lose they will go to blood vessels in the brain leading to a STROKE. Other locations where it’s common to have atherosclerositic plaque are in the femeral and iliac artery going into the leg and that can impair blood supply to your lower leg muscles. --Focus on the consequences of the heart--- Coronary Arteries- Areas at Risk of Ischemia Coronary arteries are branching off aorta, A is the coronary artery (left) ; supplies left ventricle B is the coronary artery (right) ; supplies Right ventricle Initially start on the outer surface of the heart, and as they branch into smaller arteries and then arterioles they are penetrating and sitting in the walls of ventricle. Because of their location they are susceptible to something that puts them aside from all other arteries in your body. Its due to their location within Wall of Myocardium). Wall of myocardium is every minute undergoing multiple periods of strong contraction followed by relaxation. The cardiac cycle puts stress on the coronary arteries. Coronary Artery Blood Flow graph (top line is aortic pressure purple(gives the idea of the interval systolic and diastolic interval). Aortic pressure is the driving force for moving blood through arterial circulation; you would expect that flow should follow the pattern that you see with the aortic pressure. Flow should be highest when the aortic pressure is highest, coz that’s where the gradient of pressure from the arterial to the venous side will be greatest Red Line is the measure of blood flow through the coronary artery. Left coronary artery that is supplying the left ventricle we don’t see a complete pattern , we don’t see higher flow when there is higher pressure. During Diastole beings it rebounds, and slowly follows down. During Systole we have strong reduction, in the beginning the flow goes to 0 throughout systole it remains low, Aroun
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