The Cardiovascular System: Blood Vessels, Blood Flow and Blood Pressure

Flow and a Pressure Gradient Figure 14.1 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Driving Force for Blood Flow Figure 14.2 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Pressures of the Pulmonary and Systemic Circuit Figure 14.3 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Effect of Resistance on Flow Figure 14.4 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

The Effect of Arteriole Radius on Blood Flow Regulation of radius of arterioles (and small arteries) Vasoconstriction Decrease radius  increase resistance Vasodilation Increase radius  decrease resistance Pulmonary circuit less resistance than systemic Lower pressure gradient required for blood flow Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Total Peripheral Resistance Combined resistance of all blood vessels within the systemic circuit Resistance across a network of blood vessels depends on resistance of all vessels Flow through network varies with resistance Vasoconstriction in network  increase resistance  decrease flow Vasodilation in network  decrease resistance  increase flow Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Relating Pressure Gradients and Resistance in the Systemic Circulation Flow = P /R Flow = cardiac output = CO  P = mean arterial pressure = MAP R = total peripheral resistance = TPR CO = MAP / TPR Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Types of Blood Vessels Figure 14.5 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Blood Vessel Characteristics Figure 14.6 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Arteries as Pressure Reservoirs Figure 14.7a Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Arteries as Pressure Reservoirs Figure 14.7b Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Compliance Toolbox 14.1 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Blood Pressure Measurement Systolic pressure (beginning of sounds) Diastolic pressure (end of sounds) Blood flow: Sound: No flow No sound Turbulent flow Turbulent flow in compressed artery makes audible vibrations (Korotkoff sounds) Korotkoff sounds Laminar flow Cuff pressure between 70 and 110 mm Hg Laminar flow in noncompressed artery makes no sounds below 70 mm Hg No blood flow above Pressure in the cuff Stethoscope Cuff 130 110 90 70 50 Time Figure 14.8 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Blood Pressure in Vessels Figure 14.9 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Radius Changes in Arterioles Figure 14.10 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Arteriole Radius and Blood Flow Flow varies due to differences in resistance Figure 14.11b Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Active Hyperemia Increased blood flow Delivers more O2 Removes more CO2 Figure 14.12d Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Increased blood flow in response to a previous reduction in blood flow Reactive Hyperemia Increased blood flow in response to a previous reduction in blood flow Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Characteristics of Reactive Hyperemia Blockage of blood flow to tissue Metabolites increase and oxygen decreases Vasodilation Release blockage Increased blood flow due to low resistance Metabolites removed, oxygen delivered Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Active vs. Reactive Hyperemia Local arteriolar smooth muscle O2 consumption CO2 production O2 Delivery CO2 Removal Vasodilation Blood flow O2 concentration CO2 concentration Resistance Metabolic rate Tissue Negative feedback Active Hyperemia (a) Figure 14.13a Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Active vs. Reactive Hyperemia Blood flow Resistance Reactive Hyperemia Tissue Local arteriolar smooth muscle O2 concentration CO2 concentration Vasodilation O2 Delivery CO2 Removal Negative feedback (b) Figure 14.13b Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

The Myogenic Response Figure 14.14 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Blood Flow Patterns Figure 14.15a–b Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Extrinsic Control of Arteriole Radius and Mean Arterial Pressure Flow = P/R CO = MAP / TPR MAP = CO x TPR Mean arterial pressure depends on TPR TPR depends on radius of arterioles Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Table 14.2 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Vessel Area and Velocity of Blood Capillaries Have greatest total cross-sectional area Have slowest velocity of blood flow, enhances exchange Figure 14.16 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Types of Capillaries Continuous capillaries Fenestrated capillaries Most common Small gaps between endothelial cells Allows small water soluble molecules to move through Fenestrated capillaries Large gaps between endothelial cells forming pores or fenestrations Allow proteins and in some cases blood cells to move through Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Continuous Capillary Figure 14.17a Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Fenestrated Capillary Figure 14.17b Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Microcirculation Figure 14.18 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Capillary Exchange Figure 14.19 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Starling Forces Across Capillaries Figure 14.20 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Vessel: Pressure / Volume Relation Figure 14.21 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Blood Distribution Figure 14.22 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Importance of Central Venous Pressure Pressure gradient between central veins and atria drives blood back to heart Venous pressure – atrial pressure = 5 – 10 mm Hg A decrease in venous pressure decreases driving force for venous return Decrease in venous return  decreases end- diastolic volume  decreases stroke volume  decreases cardiac output  decreases blood flow to organs Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.

Factors of Venous Pressure Figure 14.24 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings.