An imbalance in this predisposes the heart muscle to ischemia, which means reduced blood flow. The tissue death as a result of ischemia occurs because of two reasons, reduced oxygen supply and the decreased delivery of nutrients, both of which are brought in by the flow of blood though the heart muscle. The area deprived of blood supply is said to have suffered ischemic injury. The ischemic injury, if severe enough to cause the complete block of oxygen and nutrients causes death of the heart tissue, which is termed as Myocardial Infarction. Above 90% cases of myocardial infarction occur as a result of coronary artery blockage, thus the disease is also referred to as coronary artery disease. Most commonly myocardial infarction occurs from atherosclerotic plaques which block the blood supply to the heart. John survived the heart attack because of certain reasons. In many cases it is seen that the body is not able to respond the stress that it has been levied upon because of which the person dies but in the case of John it can be seen that he survived the attack. His physiological response was enhanced because of his age which have helped him to develop collateral channels. Collateral channels are the ones developed by the body which work only when the main arteries have been blocked. The atherosclerotic plaques may have forced open the collateral channels in the heart of John which helped him to normalize his blood level. The muscles which became ischemic because of the blood supply were
able to grasp enough blood so that the heart could pump the blood to other tissues. One of the main physiological response which helped John to survive the attack was the reperfusion of the heart muscles which were involved in the infarction. It is also possible that the plaques were dissolved after their lysis with the help of platelets (Kumar et al 2005) (b) What role did the immune system play, if any? The immune system did possibly play a role in the survival of John. Myocardial infarction is influenced by the development of plaques along with vasospasm. After the heart attack the white blood cells moved into the area where the blood flow was restricted to form a thrombus. This thrombus thus stopped the blood from flowing to the cardiac muscles which must have destroyed them. The platelet aggregation would have been thus stopped by other white blood cells which would have helped in the lysis of the plaque (Guyton & Hall 2011). (c) How has John's blood flow been affected by his heart attack? After the heart attack John’s blood flow to the tissues has been decreased because of several reasons. The myocardial infarction must have left some effects on the heart of John because of which his cardiac muscles were destroyed. This destruction would lower the ventricular function which would thus cause the heart to function less than its normal. It is thus observed that the systemic circulation of John would be reduced in response to the heart attack (Ganong 2005; Kumar et al 2005). References Hall, J. E., & Guyton, A. C. (2011). Guyton and Hall textbook of medical physiology. Philadelphia, Pa: Saunders/Elsevier. Kumar, V., Abbas, A. K., Fausto, N., Robbins, S. L., & Cotran, R. S. (2005). Robbins and Cotran pathologic basis of disease. Philadelphia: Elsevier Saunders. Ganong, W. F. (2005).