BIO 203 Lecture 15

BIO 203 Lecture 15 - BIO 203 Lecture 15 March 15th 2007...

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BIO 203 Lecture 15 March 15 th 2007 Peripheral resistance – resistance to blood flow closer to arterioles, central is closer to heart SA node atrium contraction AV node fibers and bundle of Hiss Perkinje fibers ventricular muscles Blood flow is opposed by the resistance of the system 3 factors – length of vascular system, blood vessel radius (arterioles), viscosity of blood (% of whole blood occupied by RBC) ^ Resistance to blood flow (cardiac output), ^ mean arterial blood pressure, cardiac output remains constant Resistance = ( 8 length of tube x viscosity) / (pi x r^4) o Length of tube, constant, except in obesity o Obesity – length of vascular system lengthened, forcing heart to work harder o Viscosity – hematocrit, normally constant o Radius – radius of tube – arteriolar radius, decrease radius by half, increase resistance sixteen fold, most significant is it is raised to the 4 th power o Vasoconstrictor – decrease radius, Norepinephrine release generates vasoconstriction o Normally, they are slightly vasoconstricted o Peripheral nervous system ACh sympathetic neuron release Norepinephrine
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This note was uploaded on 04/08/2008 for the course BIO 328 taught by Professor Cabot during the Spring '07 term at SUNY Stony Brook.

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BIO 203 Lecture 15 - BIO 203 Lecture 15 March 15th 2007...

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