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27 Cards in this Set
- Front
- Back
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Compare the brain vasculature with the rest of the body's vasculature in terms of redudancies.
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Brain vasculature has the most redundancies
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What joins the 2 carotids and the 2 vertebrals together in the brain vasculature?
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Circle of Willis
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What type of substances are diffusible through the blood brain barrier?
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Lipid soluble
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Give normal values for brain blood flow (perfusion and % of C.O.).
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750-900 ml/min which is about 15 % of cardiac output
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Besides numerous arterial and venous anastomeses what is the other unique feature of the brain's vasculature?
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It has the blood-brain barrier
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True/False: Blood flow to the brain is maintained fairly constant between perfusion pressures of 50-150 mmHg.
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TRUE
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Describe how the cerebrospinal fluid impacts the downstream pressure and consequently perfusion pressure.
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Normally, the venous pressure is used as the downstream pressure for calculating perfusion. If csf pressure is greater than venous pressure than, effectively, the csf pressure should be considered the downstream pressure (b/c the pressure collapses the cerebral veins).
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True/False: Unlike the muscles, the brain's vasculature is not sensitive to Carbon dioxide
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False! The brain's vasculature IS uniquely sensitive to carbon dioxide
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If carbon dioxide's partial pressure is doubled what will be the effect on the brain?
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The brain blood flow will also double
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What is the lowest partial pressure at which blood flow will continue to fall in the presence of carbon dioxide?
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20 mmHg carbon dioxide
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True/False: high blood carbon dioxide (hypercapnia) can disrupt brain blood flow autoregulation.
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TRUE
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What happens to blood flow when the saturation of hemoglobin falls below 90%?
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Blood flow increases
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True/False: When hemoglobin is nearly saturated, changes in oxygen have a profound effect on blood flow.
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False, they have minimal effect on blood flow
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Like high carbon dioxide, low blood oxygen (hypoxia) can ______ brain blood flow autoregulation.
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disrupt
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What is the effect of hydrogen ions released by brain tissue on the cerebral vasculature?
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Causes vasodilation.
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What effect doe the pH of the blood have on brain blood flow?
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Very little because hydrogen ions do not cross the blood brain barrier to reach vascular smooth muscle (recall only lipid soluble do)
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List two other vasodilators found in the extracellular fluid can influence flow similarly (increase results in increase in blood flow).
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Potassium ion and adenosine
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True/False: A small increase in potassium ions (extracellular) can rapidly increase blood flow and vice versa.
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TRUE
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What happens when potassium in the CSF reaches 20 mEq/L?
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Constriction (pathologic circumstance)
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How do potassium ions and adenosine found in the blood affect blood flow?
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They don't because they cannot cross the blood brain barrier
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Besides the major cerebral vasoactive metabolites (adenosine and potassium ions) list two other vasodilators.
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Nitric oxide and prostaglandins
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What is the effect of NO produced by the endothelium and brain tissue on the cerebral blood vessels?
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Dilates them
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What is the effect of prostaglandins produced by the endothelium on cerebral brain vasculature?
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Dilates them
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True/False: Normally the neural control of cerebral vasculature is minor
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TRUE
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What type of nerves (sympathetic/parasympathetic) are found in abundance on pial and circle of Willis vessels.
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Andrenergic (sympathetic)
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Give another name for adrenergic nervous system.
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Sympathetic nervous system
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What type of nerves (sympathetic/parasympathetic) are found on the pial vessels only and no function has been found?
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Cholinergic (parasympathetic)
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