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14 Cards in this Set
- Front
- Back
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Define: Property of a tissue to modulate is own blood flow independent of neural influences.
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Local Control
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Give two theories of autoregulation.
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Myogenic theory and metabolic theory
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What theory? Autoregulation is an intrinsic property of a blood vessel. When the vessel is stretched by pressure it tends to contract and compensate for the increased pressure.
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Myogenic theory
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What theory? There are vasodilator metabolites produced by the tissue that regulate vascular resistance to assure blood flow is adequate for metabolic demand.
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Metabolic theory
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What are the two hypotheses of the myogenic theory?
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Ionic hypothesis and endothelium hypothesis
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What does the ionic hypothesis of the Myogenic theory of autoregulation state?
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Stretch on a vessel alters ion channels changing the flux across the membrane and ultimately calcium flux to constrict when the pressure is high and dilate when the pressure is low.
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What does the endothelium hypothesis of the myogenic theory of autoregulation state?
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Endothelium senss changes in pressure or wall stress and releases substances to elicit the appropriate response (both dilator and constrictor substances)
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Define: An organ or tissue's ability to maintain constant blood flow in the face of a change in perfusion pressure.
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Autoregulation (of blood flow)
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What are the two assumptions inherent in the definition of autoregulation?
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1. metabolic demand is constant 2. No neural influence occurs
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Define: Higher blood flow is seen when the functional activity (metabolic work) of a tissue or organ is increased.
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Active hyperemia (or functional hyperemia or increased blood flow)
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What assumption is required per the definition of active hyperemi (blood flow increase when metabolic work increase)?
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Blood pressure is constant
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Define: Blood flow increases after a period of blood flow restriction to "pay back" the Oxygen deficit.
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Reactive hyperemia
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List six major vasoactive metabolites (vasodilator).
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Adenosine, Oxygen (lack of causes vasodilation), Potassium (Initially, inhibits smooth muscle contraction), Hydrogen ion, Carbon Dioxide, Osmolarity (increased osmolarity can cause limited dilation in some tissues.
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How negative feedback works to facilitate local blood control in terms of metabolites?
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The presence of metabolites increases vasodilation; and vasodilation increases blood flow to the tissues which washes out the metabolites.
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