KINS 1224 Lecture Notes - Lecture 9: Vasomotor Center, Laminar Flow, Hemorheology
21 Feb 2017
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Determinants of bp: resistance, cardiac output, blood volume. Resistance: friction encountered by blood through vessels. Generally from smaller vessels and arterioles: sources. Blood viscosity: defined as (cid:862)thi(cid:272)kness(cid:863) of (cid:271)lood, directly proportional to resistance. Increased viscosity increases resistance: inversely proportional to flow. Blood vessel length: distance blood must travel. Increased distance increases friction: directly proportional to resistance. Increased length of vessel increases resistance: inversely proportional to flow. Laminar flow: blood in middle goes faster because no friction: resistance to flow caries inversely with fourth power of radius. Poiseuille"s law: flow, q = change in bp x pi x r4 / 8(viscosity x length, resistance = 8(viscosity x length)/ pi x r4, resistance. Regulation of pressure and flow: local control. Ability of tissue to regulate own flow. Baroreflex: negative feedback mechanism, inhibits sns. Decrease ph, decrease o2, increase co2: primary role. Medullary ischemic reflex: autonomic response to drop in brain perfusion, cardiac and vasomotor centers. Widespread vasoconstriction: input from higher brain center.
