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35 Cards in this Set
- Front
- Back
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What is the most notable vasodialating metabolite reflecting the hearts cardiac metabolic demand?
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Adenosine
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During what cardiac cycle period does the coronary vasculature experience occlusion causing reactive hyperemia?
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systole, makes sense becuase blood flows into the coronary vessels during diastole
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How does the length of occlusion of a coronary vessel affect the flow during diastole?
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It increases the peak flow as well as the duration of that enhanced flow to allow for flushing of vasodialator metabolites
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Which coronary vessel experiences the highest degree of reactive hyperemia?
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Left coronary vessels
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How does sympathetic stimulation to the heart cause vasodialation?
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B1 stimulation increases metabolic demand and vasodialation metabolites which overcomes the effect of basal NE vasoconstriction via a1
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If parasympathetic stimulation via M3 receptors results in vasodialation why is coronary flow decreased?
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Becuase it slows heart rate and metabolic demand which decreases vasodialation metabolites which have more effect in heart
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What effect is more important in the heart, ANS stimulation or local metabolite concentrations?
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Metabolite concentrations override the effects of Neural input in the heart
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What are the autoregulation ranges for cerebral and cardiac vessels?
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50-60 to 150-160mmHg
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What are the most important vasodialator metabolites in the brain?
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CO2 and H+
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What limits the effects of many types of CIRCULATING vasodialator metabolites?
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Blood brain barrier
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If parasympathetic stimulation via M3 receptors results in vasodialation why is coronary flow decreased?
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Becuase it slows heart rate and metabolic demand which decreases vasodialation metabolites which have more effect in heart
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What effect is more important in the heart, ANS stimulation or local metabolite concentrations?
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Metabolite concentrations override the effects of Neural input in the heart
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What are the autoregulation ranges for cerebral and cardiac vessels?
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50-60 to 150-160mmHg
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What are the most important vasodialator metabolites in the brain?
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CO2 and H+
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What limits the effects of many types of vasodialator metabolites?
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Blood brain barrier
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Why doesn't O2 play as large a role in blood flow determination in the brain as CO2?
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Because low O2 only begins to affect the brain at very low O2 partial pressures. Normal levels around 100 mmHg but no effect till about 50 mmHg
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What metabolites primarily effect vasodialation in the brain?
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Adenosine, K+, NO
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If H+ can't cross the BBB how does pH drop in conditions of hypoxia?
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CO2 can cross and gets Hydrated forming carbonic acid which lowers the pH
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Describe the cushing reflex
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Increased intracranial pressure due to a CSF block will compress brain stem leading to ischemia. Body response is sympathetic vasoconstriction to raise TPR and hence MAP to favor blood flow into brain with high intracranial pressure. Barosensors also stimulate bradycardia. Remember MAP=COxTPR
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How is the CNS Ischemic response carried out?
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If BP drops below autoregulation limit of 50-60mmHg the medullary vasomotor center become ischemic and in response increases sympathetic tone to increase cranial flow. Sort of like Cushing but for low pressure
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At rest what receptors activity predominates in skeletal muscle?
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Neural control predominates at rest sympathetic a1 from NE(vasoconstriction)
There are also B2 receptors but they are only activated by epinephrine from the adrenal medualla during fight response |
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HOw is vasodilation at rest achieved in skeletal muscle?
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By with drawl of sympathetic stimulation=passive vasodilation
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What does the graph on slide 32 of lec 36-37 tell us about level of control at resting levels of sympathetic tone in skeletal muscle?
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At lower levels of sympathetic tone, small changes in the sympathetic input create large changes in Resistance of skeletal muscle allow high degree of control over flow at rest
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How do the methods of blood flow control change in skeletal muscle during exercise?
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Vasodilation of vessels due to local metabolites and B2 stimulation due to epinephrine has a large role in vasodilation
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What metabolites affect the vasodilation of exercising skeletal muscle?
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lactate, K+, and adenosine
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When it is stated that local metabolites are affecting vasodilation what intrinsic factors of flow regulation are implied?
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active\reactive hyperemia and autoregulation
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How does the muscle pump enhance blood flow?
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Intermittent contraction lowers venous pressure which increase pressure gradient favoring higher flow rate
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If epinephrine excites B2 and causes vasodilation at low levels why does your blood pressure go up during exercise?
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Because epinephrine at high concentrations will also excite a1\a2 causing vasoconstricition and increasing MAP
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How can vasopressin and angiotensin affect blood flow?
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These can also constrict vessels decreasing flow and increasing MAP
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What are the major function for controlling blood flow to the skin?
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Heat loss control and blood pressure regulation( skin can act as a reservoir to serve in times of hypovolemia)
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What are arteriovenous anastamosis of the skin and what is their function in blood flow control?
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They are shunts that provide direct route for blood from arteries to venous plexuses in the skin
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How are Ateriovenous anastamoses controlled?
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Not responsive to metabolites just sympathetic control. AVA's open with decreased sympathetic tone when the body is heated or skin exposed to prolonged cold
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What sympathetic receptors are located in the skin?
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symp. adrenergic a1-vasoconstriction AND symp. cholinergic receptors to sweat glands
NO B2 vasodilators |
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How is vasodilation caused in the skin?
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Sympathetic cholinergic receptors to sweat glands stimulate the release of bradykinin which causes active vasodilation instead of usual passive vasodilation due to withdrawl of sympathetic tone
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Skin has all the intrinsic methods of blood flow control except active hyperemia, why?
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Skin is not a highly metabolically active tissue and has high level of blood flow
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