Introduction to Human Physiology--AP 151 Lecture Outline--CARDIOVASCULAR PHYSIOLOGY I. Physical Laws Governing Blood Flow, Blood Volume, Blood Pressure, and Resistance A. Blood Flow – the volume of blood flowing through a vessel, or organ, or the entire circulation in a given period of time (ml/min). 1. If entire circulation, then blood flow = cardiac output 2. Fluid flow is directly related to a pressure gradient (∆P = P1 – P2); F ∝ ΔP 3. Flow is laminar through long, smooth-walled tubes. 4. Flow is turbulent through vessel constrictions, or over rough surfaces. B. Blood Pressure – the force blood exerts against the blood vessel walls; expressed in mm Hg C. Resistance – the opposition to flow 1. Blood flow encounters friction from vessel walls and blood cell collisions 2. Most friction encountered in peripheral circulation; therefore, aka Peripheral resistance 3. Increased resistance ------> decreased blood flow a. Flow ∝ 1/R :(i.e., Flow is inversely proportional to resistance)  As resistance increases, flow decreases  As resistance decreases, flow increases 4. Three (3) parameters determine resistance for fluid flowing through a vessel a. Vessel length (L) – longer vessels have greater resistance than shorter vessels b. Fluid viscosity ( n ) – thicker fluids have greater resistance than thinner fluids c. Vessel radius (r) – changes more often than length or viscosity  As radius increases, resistance decreases  As radius decreases, re ...
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