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14 Cards in this Set
- Front
- Back
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What factors control cerebral blood flow? |
Intracranial pressure Mean arterial pressure Mean venous pressure Autoregulation (local constrict/dilate cerebral arterioles) Blood viscosity |
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What is autoregulation? |
Autoregulation is the process by which cerebral blood flow is maintained at a constant level = 54ml/100mg/min despite wide variations in perfusion pressure MAP = 50 - 150mmHg |
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What is the monroe-kellie doctrine |
Blood volume (75ml) + CSF (75ml) + Brain tissue (1400g) in the cranium at any one time remains relatively constant due to the rigid structure Therefore raised ICP, cerebral vessels compressed leading to reduced cerebral blood flow |
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What substances are important for brain metabolism |
O2 Glucose Glutamate |
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Describe the autoregulation of tissue blood flow |
Ability of tissues to maintain constant blood flow despite wide variations in perfusion pressure, via alterations in vascular resistance |
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What are the proposed mechanisms involved in autoregulation? |
Myogenic: intrinsic contractile response of smooth muscle to stretch Metabolic: active metabolites cause vasodilation accumulation assoc w/ decreased blood flow decreased pO2, pH, increased pCO2, T, K, lactate, NO |
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What local factors can cause vasoconstriction/vasodilation |
Vasodilation: decreased pO2, pH, increased pCO2, T, lactate, NO, adenosine Vasoconstriction: decreased T, autoregulation |
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Describe how blood flow is regulated at the level of the endothelium? |
Vasodilators: prostacyclins, NO, kinin Vasoconstrictors: endothelin, thromboxane, serotonin |
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What other general effects do endothelins have on the CVS system? |
+ inotrope + chronotrope Rise in ANP/renin/aldosterone Decreased GFR + renal blood flow |
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Describe the ABO blood types and their inheritance |
O - no Ag (universal donor), AntiA and AntiB Ab A - antiB Ab B - Anti A Ab AB - both Ag, no Ab (universal recipient) |
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Why is group O blood used as a universal donor? |
Because it has no Ag, both AntiA and AntiB Ab |
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How does the Rh system differ? |
Rh -ve, Rh +ve baby, immune system will recognise Rh +ve cells and produce Ab against Rh +ve blood cells If conceives a second Rh +ve baby, Ab can destroy fetal RBC, risk of haemolytic disease of newborn |
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Please draw a diagram of the changes in systolic and diastolic pressure as blood flows through the systemic circulation |
aorta/art press systole/diastole 120/80 falls as arterioles, cap, venules, veins + IVC Med and large arteries resistance to flow is low, thus pressure falls slightly Pressure falls more rapidly in small arteries + arterioles as PVR higher Pulse pressure 5mmHg at end of arterioles |
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How does the total cross sectional area of vessels change throughout the systemic circulation? |
Largest total cross sectional area in capillaries and venules |
