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Unformatted text preview: the Factors Determining the Workload of the Heart Preload Volume of blood it pumps out Amount of blood pumped with each beat, based on venous return to the heart and stretch of muscle Afterload The pressure it must generate to pump the blood out of the heart and into the aorta Flow and force in the vessels
Flow and force in the vessels If you change anything in
the lumen of a vessel you
disturb laminar flow. Laminar blood flow
Laminar blood flow Layering of blood components in the center of the bloodstream
Reduces frictional forces and prevents clotting factors from coming in contact with the vessel wall Turbulent flow
Turbulent flow Disordered flow
The blood moves crosswise and lengthwise in blood vessels Laplace’s Law
Laplace’s Law Describes the relation between wall tension, transmural pressure, and radius (of vessel) States that wall tension becomes greater as the radius increases
Wall tension is also affected by wall thickness; it increases as the wall becomes thinner and decreases as the wall becomes Laplace Law Applied
Laplace Law Applied An aneurism is w
wall of the vesse
it. The Laplace law relates pressure (P), tension (T), and radius in a cylindrical blood vessel. The pressure expanding the vessel is equal to the wall tension divided by the vessel radius. (From Rhoades R. A., Tanner G. A. . Medical physiology [Figure 163B, p. 627]. Laplace Law Laplace Law Applied Effect of the radius of a cylinder on tension. In a balloon, the tension in the wall is proportional to the radius because the pressure is the same everywhere inside the balloon. The tension is lower in the portion of the balloon with the smaller radius. (From Rhoades R. A., Tanner G. A. . Medical physiology Figure 163B [p. 627]. Boston: Little, Brown.) Problems
Problems Cardiovascular Tutorial Cardiovascular Tutorial http://www.cvphysiology.com/Tutorials/tutorials.htm QUESTIONS?
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This document was uploaded on 03/05/2014 for the course NURS 115 at Liberty University Duplicate.
- Spring '12