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14 Cards in this Set

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Define: Property of a tissue to modulate is own blood flow independent of neural influences.
Local Control
Give two theories of autoregulation.
Myogenic theory and metabolic theory
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.
Myogenic theory
What theory? There are vasodilator metabolites produced by the tissue that regulate vascular resistance to assure blood flow is adequate for metabolic demand.
Metabolic theory
What are the two hypotheses of the myogenic theory?
Ionic hypothesis and endothelium hypothesis
What does the ionic hypothesis of the Myogenic theory of autoregulation state?
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.
What does the endothelium hypothesis of the myogenic theory of autoregulation state?
Endothelium senss changes in pressure or wall stress and releases substances to elicit the appropriate response (both dilator and constrictor substances)
Define: An organ or tissue's ability to maintain constant blood flow in the face of a change in perfusion pressure.
Autoregulation (of blood flow)
What are the two assumptions inherent in the definition of autoregulation?
1. metabolic demand is constant 2. No neural influence occurs
Define: Higher blood flow is seen when the functional activity (metabolic work) of a tissue or organ is increased.
Active hyperemia (or functional hyperemia or increased blood flow)
What assumption is required per the definition of active hyperemi (blood flow increase when metabolic work increase)?
Blood pressure is constant
Define: Blood flow increases after a period of blood flow restriction to "pay back" the Oxygen deficit.
Reactive hyperemia
List six major vasoactive metabolites (vasodilator).
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.
How negative feedback works to facilitate local blood control in terms of metabolites?
The presence of metabolites increases vasodilation; and vasodilation increases blood flow to the tissues which washes out the metabolites.