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13 Cards in this Set
- Front
- Back
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major coronary vessels effect on resistance
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major vessels offer low-resistance
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branching of coronary arteries
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-major vessels
-branch to form- MICROVASCULAR RESISTANCE VESSELS (regulate coronary blood flow) -give rise to dense network of capillaries (each myocyte is associated with several capillaries ensuring short diffusion distances) |
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drainage of coronary veins
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-into right atrium via coronary sinus
-directly into chambers via anteror cardiac veins and Thebesian veins |
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regions of the heart most susceptible to ischaemic injury. why?
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SUBENDOCARDIAL REGIONS - suffer the greatest effect of reduced flow during systole
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what is the most important pressure in perfusing coronary vessels?
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aortic pressure during diastole
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what happens to coronary perfusion in tachycardia, how is it compensated for? why doesn't this work so well in diseased arteries?
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-shorter diastolic time
-coronary arteries dilate in response to local metabolic mechanisms (eg. adenosine) -diseased arteries have reduced vasodilator reserve |
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coronary flow primarily regulated by...
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tissue metabolism
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sympathetic activation affect on coronary flow
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-TRANSIENT alpha 1 receptor mediated vasoconstriction (few alpha 1 receptors on cardiac muscle)
-beta 1 receptor increase of HR and CONTRACTILITY - leading to increase of metabolites and VASODILATION, increase flow |
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parasympathetic activation affect on coronary flow
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-ACh causes modest vasodilation
-decreased HR, and if significant decrease in myocardial oxygen demand ocal metabolic mechanisms cause vasoconstriction and reduce flow |
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drop in what ratio causes symptoms of coronary artery disease?
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oxygen supply:demand
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how stenosed does a coronary artery need to be to cause significant effect on resting blood flow?
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60-70%
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atherosclerosis causes damage to endothelium, how does this affect constriction/dilation of coronary vessels?
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-can cause vasospasm
-impairs vasodilation (and therefore vasodilator reserve capacity) |
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effects of fall in oxygen supply:demand ratio
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-hypoxic myocardium
-pain -impaired mechanical function -precipitate arrythmias |
