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Chapter 15b

Chapter 15b. Blood Flow and the Control of Blood Pressure. Arteriolar Resistance. Arteriolar resistance is influenced by both local and systemic control mechanisms Local control Sympathetic reflexes Hormones. Arteriolar Resistance. Table 15-2. Arteriolar Resistance.

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Chapter 15b

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  1. Chapter 15b Blood Flow and the Control of Blood Pressure

  2. Arteriolar Resistance • Arteriolar resistance is influenced by both local and systemic control mechanisms • Local control • Sympathetic reflexes • Hormones

  3. Arteriolar Resistance Table 15-2

  4. Arteriolar Resistance • Myogenic autoregulation • Paracrines • Active hyperemia • Reactive hyperemia • Sympathetic control • SNS: norepinephrine • Adrenal medulla: epinephrine

  5. Hyperemia is a Locally Mediated Increase in Blood Flow Figure 15-11a

  6. Hyperemia is a Locally Mediated Increase in Blood Flow Figure 15-11b

  7. Norepinephrine • Tonic control of arteriolar diameter Figure 15-12

  8. Distribution of Blood • Distribution of blood in the body at rest Figure 15-14

  9. Blood Flow • Blood flow through individual blood vessels is determined by vessel’s resistance to flow Figure 15-15a

  10. Blood Flow • Flow  1/resistance Figure 15-15b

  11. Precapillary Sphincters Figure 15-16a

  12. Precapillary Sphincters Figure 15-16b

  13. Capillaries: Exchange • Plasma and cells exchange materials across thin capillary wall • Capillary density is related to metabolic activity of cells • Capillaries have the thinnest walls • Single layer of flattened endothelial cells • Supported by basal lamina • Bone marrow, liver and spleen do not have typical capillaries but sinusoids

  14. Two Types of Capillaries Nucleus Endothelial cells Endothelial celljunctions Basementmembrane Transcytosisvesicles (a) Continuous capillaries have leaky junctions. Figure 15-17a

  15. Two Types of Capillaries Fenestratedpores Basementmembrane (cut) Transcytosis vesicles Fenestrationsor pores Endothelial celljunction junction Basementmembrane (b) Fenestrated capillaries have large pores. Figure 15-17b

  16. Velocity of Blood Flow • Velocity of flow depends on total cross-sectional area of the vessels Figure 15-18

  17. Capillary Exchange • Exchange between plasma and interstitial fluid occurs by paracellular pathway or endothelial transport • Small dissolved solutes and gasses move by diffusion • Larger solutes and proteins move by vesicular transport • In most capillaries, large proteins are transported by transcytosis

  18. Capillary Exchange • Bulk flow • Mass movement as a result of hydrostatic or osmotic pressure gradients • Absorption: fluid movement into capillaries • Net absorption at venous end • Filtration: fluid movement out of capillaries • Caused by hydrostatic pressure • Net filtration at arterial end

  19. Fluid Exchange at a Capillary • Hydrostatic pressure and osmotic pressure regulate bulk flow Figure 15-19a

  20. Autoregulation and Capillary Dynamics PLAY Interactive Physiology® Animation:Cardiovascular System: Autoregulation and Capillary Dynamics

  21. Lymphatic System • Returning fluid and proteins to circulatory system • Picking up fat absorbed and transferring it to circulatory system • Serving as filter for pathogens

  22. Fluid Exchange at a Capillary Venule Arteriole Netfiltration Netabsorption Lymphvessels (b) Relationship between capillaries and lymph vessels Figure 15-19b

  23. Lymphatic System Thoracic (left lymph) duct Lymphatics ofupper limb Cervicallymph nodes Right lymph duct Thymus Axillary lymph nodes Thoracic duct Lymphatics ofmammary gland Lumbarlymph nodes Spleen Pelviclymph nodes Inguinallymph nodes Lymphaticsof lower limb Blind-end lymphcapillaries in the tissuesremove fluid and filteredproteins. Lymph fluid empties into the venous circulation. Figure 15-20

  24. Edema • Two causes • Inadequate drainage of lymph • Filtration far greater than absorption • Disruption of balance between filtration and absorption • Increase in hydrostatic pressure • Decrease in plasma protein concentration • Increase in interstitial proteins

  25. Blood Pressure • Components of the baroreceptor reflex KEY Stimulus Sensory receptor Medullarycardiovascularcontrol center Integrating center Efferent path Effector Change inbloodpressure Parasympatheticneurons Carotid and aorticbaroreceptors Sympatheticneurons SA node Ventricles Veins Arterioles Figure 15-22

  26. Blood Pressure KEY Stimulus Sensory receptor Integrating center Efferent path Effector Change inbloodpressure Figure 15-22 (1 of 10)

  27. Blood Pressure KEY Stimulus Sensory receptor Integrating center Efferent path Effector Change inbloodpressure Carotid and aorticbaroreceptors Figure 15-22 (2 of 10)

  28. Blood Pressure KEY Stimulus Sensory receptor Medullarycardiovascularcontrol center Integrating center Efferent path Effector Change inbloodpressure Carotid and aorticbaroreceptors Figure 15-22 (3 of 10)

  29. Blood Pressure KEY Stimulus Sensory receptor Medullarycardiovascularcontrol center Integrating center Efferent path Effector Change inbloodpressure Parasympatheticneurons Carotid and aorticbaroreceptors Figure 15-22 (4 of 10)

  30. Blood Pressure KEY Stimulus Sensory receptor Medullarycardiovascularcontrol center Integrating center Efferent path Effector Change inbloodpressure Parasympatheticneurons Carotid and aorticbaroreceptors Sympatheticneurons Figure 15-22 (5 of 10)

  31. Blood Pressure KEY Stimulus Sensory receptor Medullarycardiovascularcontrol center Integrating center Efferent path Effector Change inbloodpressure Parasympatheticneurons Carotid and aorticbaroreceptors Sympatheticneurons SA node Figure 15-22 (6 of 10)

  32. Blood Pressure KEY Stimulus Sensory receptor Medullarycardiovascularcontrol center Integrating center Efferent path Effector Change inbloodpressure Parasympatheticneurons Carotid and aorticbaroreceptors Sympatheticneurons SA node Figure 15-22 (7 of 10)

  33. Blood Pressure KEY Stimulus Sensory receptor Medullarycardiovascularcontrol center Integrating center Efferent path Effector Change inbloodpressure Parasympatheticneurons Carotid and aorticbaroreceptors Sympatheticneurons SA node Ventricles Figure 15-22 (8 of 10)

  34. Blood Pressure KEY Stimulus Sensory receptor Medullarycardiovascularcontrol center Integrating center Efferent path Effector Change inbloodpressure Parasympatheticneurons Carotid and aorticbaroreceptors Sympatheticneurons SA node Ventricles Arterioles Figure 15-22 (9 of 10)

  35. Blood Pressure KEY Stimulus Sensory receptor Medullarycardiovascularcontrol center Integrating center Efferent path Effector Change inbloodpressure Parasympatheticneurons Carotid and aorticbaroreceptors Sympatheticneurons SA node Ventricles Veins Arterioles Figure 15-22 (10 of 10)

  36. Blood Pressure • The baroreceptor reflex: the response to increased blood pressure Figure 15-23

  37. Blood Pressure • The baroreceptor reflex: the response to orthostatic hypotension Figure 15-24

  38. Blood Pressure Regulation PLAY Interactive Physiology® Animation:Cardiovascular System: Blood Pressure Regulation

  39. CVD: Risk Factors • Not controllable • Sex • Age • Family history • Controllable • Smoking • Obesity • Sedentary lifestyle • Untreated hypertension

  40. CVD: Risk Factors • Uncontrollable genetic but modifiable lifestyle • Blood lipids • Leads to atherosclerosis • HDL-C versus LDL-C • Diabetes mellitus • Metabolic disorder contributes to development of atherosclerosis

  41. LDL and Plaque • The development of atherosclerotic plaques Endothelial cells Elastic connective tissue Smooth muscle cells (a) Normal arterial wall LDL cholesterol accumulates Macrophages Smooth muscle cells (b) Fatty streak A lipid core accumulates Fibrous scar tissue Smooth muscle cells Calcifications are depositedwithin the plaque. (c) Stable fibrous plaque Platelets Macrophages (d) Vulnerable plaque Figure 15-25

  42. LDL and Plaque Endothelial cells Elastic connective tissue Smooth muscle cells (a) Normal arterial wall Figure 15-25a

  43. LDL and Plaque LDL cholesterol accumulates Macrophages Smooth muscle cells (b) Fatty streak Figure 15-25b

  44. LDL and Plaque A lipid core accumulates Fibrous scar tissue Smooth muscle cells Calcifications are depositedwithin the plaque. (c) Stable fibrous plaque Figure 15-25c

  45. LDL and Plaque Platelets Macrophages (d) Vulnerable plaque Figure 15-25d

  46. Hypertension • The risk of developing cardiovascular disease doubles with each 20/10 mm Hg increase in blood pressure • Essential hypertension has no clear cause other than hereditary Figure 15-26

  47. Hypertension • Carotid and aortic baroreceptors adapt • Risk factor for atherosclerosis • Heart muscle hypertrophies • Pulmonary edema • Congestive heart failure • Treatment • Calcium channel blockers, diuretics, beta-blocking drugs, and ACE inhibitors

  48. Summary • Blood vessels • Vascular smooth muscle, metarterioles, venules, and angiogenesis • Measuring blood pressure • Systolic pressure, diastolic pressure, pulse pressure, MAP, and Korotkoff sounds • Resistance in the arterioles • Myogenic autoregulation, active hyperemia, and reactive hyperemia

  49. Summary • Distribution of blood • Capillary exchange • Continuous capillaries, fenestrated capillaries, bulk flow, filtration, absorption, and colloid osmotic pressure • Lymphatic system • Blood pressure regulation • Baroreceptors, baroreceptor reflex, and cardiovascular control center • Cardiovascular disease

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