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Canada (511,194)
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KNES 260 (23)


8 Pages

Course Code
KNES 260
Ronald Reed Ferber

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HEMODYNAMICS: PRESSURE, FLOW AND RESISTANCE Epinephrine released from adrenal medulla: • primarily acts on beta-2 type adrenergic receptors – found mostly in heart and skeletal muscle. • Activation of beta 2 receptors results in vasodilation. Beta-2 adrenergic receptor activation: o Epinephrine is a hormone o Epinephrine creates an increase in blood supply o Depending on where, Epinephrine can cause vasodilation (in heart and skeletal muscles) and vasoconstriction (digestive tract) Vasodilation Relaxation of vascular  smooth muscle Active Hyperemia: a local reflex o Increase in blood flow to a tissue in  response to increase metabolites (CO   2 and lactic acid) in the interstitial fluid  of that tissue. o Depletion of O  al2o causes active  hyperemia o Norepinephrine=neurotransmitter o Epinephrine=hormone (blood  circulation) Lactic Acid increses  Do not need to know constricts Other local dilators: 1. nitric oxide (NO)- (gas) produced by endothelial cells of a vessel  diffuses into vascular smooth muscle  Relaxation  Vasodilation 2. Histamine – produced by mast cell in the immune system in response to an allergen or tissue damagevasodilation increase blood flow to tissue  tissue swelling Microcirculation and exchange across capillary walls: o Metarteriole is a shunt. o Precapillary sphincters open in  response to local factors like increase  in CO 2and lactic acid and increase in  O 2 • Most capillary beds (about 90%) in muscle tissue are closed under resting conditions: • Blood is shunted through metarterioles to venules when the pre-capillary sphincters are closed Pre-capillary sphincters open in response to: local factors o Red blood cells must squeeze through capillaries one at a time o This is good because it allows enough time for gas exchange to occur Capillaries: where the exchange of nutrients and waste products of metabolism and oxygen and carbon dioxide occurs Features: o Capillaries are one endothelial cell thick o No vascular smooth muscle. Movement across the capillary: 1. Simple diffusion – movement of solute down a concentration gradient between blood plasma and interstitial fluid. 2. Bul
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