ECE_3820_lecture_20_2011

ECE_3820_lecture_20_2011 - Today (11/08), lecture #20 The...

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Unformatted text preview: Today (11/08), lecture #20 The heart! Thursday (11/10), Exam #2 Bring your calculator. Material to study: A) All lecture notes (lectures 12-20). Study the slides and the notes that were written on the board. B) All concepts addressed in homework sets 4, 5, and 6. HW Set #6 : The answers are available on Blackboard. Hint for Problem 5 of Hw Set #5 k g j y y x a i xy x a k z P j y P i x P P ) ( 2 ) ( 2 3 2 2 2 3 2 + + = + + = dt dV z V y V x V x P g x x x x x = + + + 2 2 2 2 2 2 dt dV z V y V x V y P g y y y y y = + + + 2 2 2 2 2 2 dt dV z V y V x V z P g z z z z z = + + + 2 2 2 2 2 2 Use the Navier-Stokes equations for Cartesian coordinates z V V y V V x V V t V dt V d z y x + + + = And the derivative of the velocity field To write the pressure gradient field Blood Pressure A) Pulse pressure: the difference between systolic and diastolic pressure. B) Changes associated with systole: Aorta is stretched by blood leaving left ventricle (energy is stored). Blood moves toward periphery because peripheral pressure is lower than aortic pressure. C) Changes associated with diastole: The aorta recoils, which generates pressure by volume reduction. D) The pulse pressure is zero in the small arterioles. Windkessel Effect : large arteries (aorta) act as an elastic (and temporary) reservoir of blood. Large arteries behave as a low-pass filter: high frequency components are filtered out, resulting in steady (nonpulsatile) flow in the capillaries. 1) During rapid cardiac ejection, inertia and resistance forces make it difficult for the ejected volume to quickly push the blood already present in the aorta. 2) As a result, most of the stroke volume is accommodated by stretching the elastic wall and increasing the volume of the proximal aorta. (kinetic energy is stored as elastic energy) 3) This aortic stretch (potential energy) maintains aortic pressure during diastole and thereby permits continuous forward flow of blood. 4% 4% 4% 16% 64% Pressure Volume Arterioles Capillaries Veins Arteries Aorta Pulmonary arteries Veins are low pressure blood storage reservoirs! storage reservoirs!...
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ECE_3820_lecture_20_2011 - Today (11/08), lecture #20 The...

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