Term
| define arteriosclerosis and atherosclerosis. |
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Definition
arteriosclerosis - hardening of the arteries
atherosclerosis - plaque buildup in the arteries |
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Term
| what prevents complete ischemia from an occlusion in the coronary circulation? |
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Definition
| there is a lot of collateralization among the arteries |
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Term
| list the three layers of the myocardium. |
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Definition
| subendocardial, subepicardial, and middle layers |
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Term
| describe how high left ventricular pressure affects blood supply through the coronary arteries. |
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Definition
| coronary arteries are perfused by the same pressure as the aorta (120/80) but the left ventricular myocardium pressure is much greater (150) due to contraction. This means that the LV is not perfused during systole, but instead during diastole, the RV is not affected by this however because its pressure is much lower |
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Term
| where is the greatest intramyocardial pressure located and what implications does this have? |
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Definition
| in the subendocardial layer nearest the endocardium, this means that the majority of MI's are seen in the LV subendocardial layers due to difficulty perfusing blood to this region. |
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Term
| describe the differences between LCA and RCA perfusion during heart contraction. |
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Definition
RCA pressure mimics that of the aorta in which the highest perfusion pressure is during systole, whereas the LCA due to high pressure in the LV dips during isovolumic contraction and sees its highest perfusion pressure during isovolumic relaxation and diastole
the LCA also sees dramatic vasodilation due to metabolite buildup during systole that also increases perfusion pressure |
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Term
| what is the most important coronary artery vasodilator and when is it released? |
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Definition
| adenosine, during contraction |
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Term
| describe the role of the ANS on coronary artery circulation. |
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Definition
| the ANS does not play a significant role in controlling perfusion due to the much larger affect from the metabolites being produced, however in a diseased heart in which tissue is desensitized to metabolites the ANS can override the metabolic response and cause an MI during periods of stress |
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Term
| describe the O2 supply/demand balance conundrum of a bad heart. |
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Definition
| the LV pressure is thought of as the demand for O2, and the diastolic pressure is thought of as the supply of O2 since the LV is perfused during diastole. in order to avoid overworking the heart, you want to keep systolic pressure low and diastolic pressure high such as with a counter pulsation device |
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Term
| what is the circle of willis and what function does it peform? |
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Definition
| it is a ring of arteries located at the base of the brain that supplies the cerebral circulation, it also provides collateralization in the instance of a blockage |
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Term
| why is a constant cerebral blood flow important and how is it maintained? |
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Definition
| because it can be damaged by too high and too low of blood due to increased pressure and edema or not enough oxygen, the flow is held constant mainly by the myogenic reflex in which an increase in pressure leads to vasoconstriction and a decrease leads to vasodilation |
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Term
| how does the cerebral circulation adjust to chronic changes in blood flow? |
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Definition
| via autoregulation it move its set point to accomodate the new blood flow based on MAP |
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Term
| how does the brain monitor oxygen levels and what role doe they play in cerebral circulation? |
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Definition
| indirectly by measuring CO2 levels, because O2 levels do not change much throughout the body it is not a large controller of cerebral flow |
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Term
| what is the CNS ischemic reflex and the cushing's phenomenon? |
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Definition
| if the O2 levels in the brain decrease dramatically than blood pressure is elevated dramatically to increase cerebral flow, however baroreceptors in turn slow down the HR in response to the elevated BP |
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Term
| describe the difference between local and global cerebral artery flow. |
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Definition
| the overall global flow is held constant due to myogenic reflexes, however local regions of the brain receive more blood during periods of stimulation due to increased metabolite production |
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