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This 6 page Class Notes was uploaded by Jess Graff on Tuesday March 1, 2016. The Class Notes belongs to BMS 508 at University of New Hampshire taught by Mary Katherine Lockwood, PhD in Spring 2016. Since its upload, it has received 14 views. For similar materials see Human Anatomy and Physiology II in Biological Sciences at University of New Hampshire.
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Date Created: 03/01/16
BMS 508.03 2/26/16 Chapter 20 (cont) Blood Vessels and Circulation (cont) Pressure and Resistance (cont) • An Overview of Cardiovascular Pressures • Vessel diameters • Total cross-sectional areas • Pressures • Velocity of blood flow • Arterial Blood Pressure • Systolic pressure • Peak arterial pressure during ventricular systole • Diastolic pressure • Minimum arterial pressure during diastole • Pulse pressure • Difference between systolic pressure and diastolic pressure • Mean arterial pressure (MAP) • MAP = diastolic pressure + 1/3 pulse pressure • Abnormal Blood Pressure • Normal = 120/80 • Hypertension • Abnormally high blood pressure • Greater than 140/90 • Hypotension • Abnormally low blood pressure • Elastic Rebound • Arterial walls • Stretch during systole • Rebound (recoil to original shape) during diastole • Keep blood moving during diastole • Pressures in Small Arteries and Arterioles • Pressure and distance • MAP and pulse pressure decrease with distance from heart • Blood pressure decreases with friction • Pulse pressure decreases due to elastic rebound • Venous Pressure and Venous Return • Determines the amount of blood arriving at right atrium each minute • Low effective pressure in venous system • Low venous resistance is assisted by: • Muscular compression of peripheral veins • Compression of skeletal muscles pushes blood toward heart (one-way valves) • The respiratory pump • Thoracic cavity action • Inhaling decreases thoracic pressure • Exhaling raises thoracic pressure • Capillary Pressures and Capillary Exchange • Vital to homeostasis • Moves materials across capillary walls by: • Diffusion • Filtration • Reabsorption • Diffusion • Movement of ions or molecules • From high concentration • To lower concentration • Along the concentration gradient • Diffusion Routes • Water, ions, and small molecules such as glucose • Diffuse between adjacent endothelial cells or through fenestrated capillaries • Some ions (Na , K , Ca , Cl ) − • Diffuse through channels in plasma membranes • Large, water-soluble compounds • Pass through fenestrated capillaries • Lipids and lipid-soluble materials such as O and CO 2 2 • Diffuse through endothelial plasma membranes • Plasma proteins • Cross endothelial lining in sinusoids • Filtration • Driven by hydrostatic pressure • Water and small solutes forced through capillary wall • Leaves larger solutes in bloodstream • Reabsorption • The result of osmotic pressure (OP) • Blood colloid osmotic pressure (BCOP) • Equals pressure required to prevent osmosis • Caused by suspended blood proteins that are too large to cross capillary walls • Interplay between Filtration and Reabsorption • Ensures that plasma and interstitial fluid are in constant communication and mutual exchange • Accelerates distribution of: • Nutrients, hormones, and dissolved gases throughout tissues • Assists in the transport of: • Insoluble lipids and tissue proteins that cannot enter bloodstream by crossing capillary walls • Has a flushing action that carries bacterial toxins and other chemical stimuli to: • Lymphatic tissues and organs responsible for providing immunity to disease • Net hydrostatic pressure • Forces water out of solution • Net osmotic pressure • Forces water into solution • Both control filtration and reabsorption through capillaries • Factors that Contribute to Net Hydrostatic Pressure • Capillary hydrostatic pressure (CHP) • Interstitial fluid hydrostatic pressure (IHP) • Net capillary hydrostatic pressure tends to push water and solutes: • Out of capillaries • Into interstitial fluid • Net Capillary Colloid Osmotic Pressure • The difference between: • Blood colloid osmotic pressure (BCOP) and • Interstitial fluid colloid osmotic pressure (ICOP) • Pulls water and solutes: • Into a capillary from interstitial fluid • Net Filtration Pressure (NFP) • The difference between: • Net hydrostatic pressure • Net osmotic pressure NFP = (CHP – IHP) – (BCOP – ICOP) • Capillary Exchange • At arterial end of capillary: • Fluid moves out of capillary • Into interstitial fluid • At venous end of capillary: • Fluid moves into capillary • Out of interstitial fluid • Transition point between filtration and reabsorption • Is closer to venous end than arterial end • Capillaries filter more than they reabsorb • Excess fluid enters lymphatic vessels • Capillary Dynamics • Hemorrhaging • Reduces CHP and NFP • Increases reabsorption of interstitial fluid (recall of fluids) • Dehydration • Increases BCOP • Accelerates reabsorption • Increase in CHP or BCOP declines • Fluid moves out of blood • Builds up in peripheral tissues (edema)