Chapter 15b Blood Flow and the Control of Blood Pressure.
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Transcript of Chapter 15b Blood Flow and the Control of Blood Pressure.
![Page 1: Chapter 15b Blood Flow and the Control of Blood Pressure.](https://reader036.fdocuments.us/reader036/viewer/2022081504/551c25c6550346b24f8b5e2b/html5/thumbnails/1.jpg)
Chapter 15b
Blood Flow and the Control of Blood
Pressure
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Arteriolar Resistance
• Arteriolar resistance is influenced by both local and systemic control mechanisms• Local control• Sympathetic reflexes• Hormones
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Arteriolar Resistance
Table 15-2
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Arteriolar Resistance
• Myogenic autoregulation• Paracrines• Active hyperemia• Reactive hyperemia
• Sympathetic control• SNS: norepinephrine• Adrenal medulla: epinephrine
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Hyperemia is a Locally Mediated Increase in Blood Flow
Figure 15-11a
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Hyperemia is a Locally Mediated Increase in Blood Flow
Figure 15-11b
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Norepinephrine
• Tonic control of arteriolar diameter
Figure 15-12
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Distribution of Blood
• Distribution of blood in the body at rest
Figure 15-14
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Blood Flow
• Blood flow through individual blood vessels is determined by vessel’s resistance to flow
Figure 15-15a
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Blood Flow
• Flow 1/resistance
Figure 15-15b
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Precapillary Sphincters
Figure 15-16a
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Precapillary Sphincters
Figure 15-16b
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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
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Two Types of Capillaries
Figure 15-17a
Basementmembrane
Endothelial celljunctions
Transcytosisvesicles
Endothelial cells
Nucleus
(a) Continuous capillaries have leaky junctions.
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Two Types of Capillaries
Basementmembrane (cut)
Basementmembrane
Endothelial celljunctionjunction
Transcytosis vesicles
Fenestratedpores
(b) Fenestrated capillaries have large pores.
Fenestrationsor pores
Figure 15-17b
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Velocity of Blood Flow
• Velocity of flow depends on total cross-sectional area of the vessels
Figure 15-18
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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
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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
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Fluid Exchange at a Capillary
• Hydrostatic pressure and osmotic pressure regulate bulk flow
Figure 15-19a
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Autoregulation and Capillary Dynamics
PLAY Interactive Physiology® Animation: Cardiovascular System: Autoregulation and Capillary Dynamics
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Lymphatic System
• Returning fluid and proteins to circulatory system
• Picking up fat absorbed and transferring it to circulatory system
• Serving as filter for pathogens
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Fluid Exchange at a Capillary
Figure 15-19b
Arteriole
Netabsorption
Lymphvessels
Netfiltration
Venule
(b) Relationship between capillaries and lymph vessels
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Lymphatic System
Figure 15-20
Thoracic (left lymph) duct
Axillary lymph nodes
Lymphatics ofmammary gland
Spleen
Pelviclymph nodes
Inguinallymph nodes
Thoracic duct
Thymus
Right lymph duct
Cervicallymph nodes
Blind-end lymphcapillaries in the tissuesremove fluid and filteredproteins.
Lymph fluid empties into the venous circulation.
Lymphatics ofupper limb
Lumbarlymph nodes
Lymphaticsof lower limb
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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
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Blood Pressure
• Components of the baroreceptor reflex
Figure 15-22
Medullarycardiovascularcontrol center
Carotid and aorticbaroreceptors
Change inblood
pressure
Parasympatheticneurons
Sympatheticneurons
Veins
Arterioles
Ventricles
SA node
Integrating center
Stimulus
Efferent path
Effector
Sensory receptor
KEY
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Change inblood
pressure
Integrating center
Stimulus
Efferent path
Effector
Sensory receptor
KEY
Blood Pressure
Figure 15-22 (1 of 10)
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Carotid and aorticbaroreceptors
Change inblood
pressure
Integrating center
Stimulus
Efferent path
Effector
Sensory receptor
KEY
Blood Pressure
Figure 15-22 (2 of 10)
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Medullarycardiovascularcontrol center
Carotid and aorticbaroreceptors
Change inblood
pressure
Integrating center
Stimulus
Efferent path
Effector
Sensory receptor
KEY
Blood Pressure
Figure 15-22 (3 of 10)
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Medullarycardiovascularcontrol center
Carotid and aorticbaroreceptors
Change inblood
pressure
Parasympatheticneurons
Integrating center
Stimulus
Efferent path
Effector
Sensory receptor
KEY
Blood Pressure
Figure 15-22 (4 of 10)
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Medullarycardiovascularcontrol center
Carotid and aorticbaroreceptors
Change inblood
pressure
Parasympatheticneurons
Sympatheticneurons
Integrating center
Stimulus
Efferent path
Effector
Sensory receptor
KEY
Blood Pressure
Figure 15-22 (5 of 10)
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Medullarycardiovascularcontrol center
Carotid and aorticbaroreceptors
Change inblood
pressure
Parasympatheticneurons
Sympatheticneurons SA node
Integrating center
Stimulus
Efferent path
Effector
Sensory receptor
KEY
Blood Pressure
Figure 15-22 (6 of 10)
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Medullarycardiovascularcontrol center
Carotid and aorticbaroreceptors
Change inblood
pressure
Parasympatheticneurons
Sympatheticneurons SA node
Integrating center
Stimulus
Efferent path
Effector
Sensory receptor
KEY
Blood Pressure
Figure 15-22 (7 of 10)
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Medullarycardiovascularcontrol center
Carotid and aorticbaroreceptors
Change inblood
pressure
Parasympatheticneurons
Sympatheticneurons
Ventricles
SA node
Integrating center
Stimulus
Efferent path
Effector
Sensory receptor
KEY
Blood Pressure
Figure 15-22 (8 of 10)
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Medullarycardiovascularcontrol center
Carotid and aorticbaroreceptors
Change inblood
pressure
Parasympatheticneurons
Sympatheticneurons
Arterioles
Ventricles
SA node
Integrating center
Stimulus
Efferent path
Effector
Sensory receptor
KEY
Blood Pressure
Figure 15-22 (9 of 10)
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Medullarycardiovascularcontrol center
Carotid and aorticbaroreceptors
Change inblood
pressure
Parasympatheticneurons
Sympatheticneurons
Veins
Arterioles
Ventricles
SA node
Integrating center
Stimulus
Efferent path
Effector
Sensory receptor
KEY
Blood Pressure
Figure 15-22 (10 of 10)
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Blood Pressure
• The baroreceptor reflex: the response to increased blood pressure
Figure 15-23
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Blood Pressure
• The baroreceptor reflex: the response to orthostatic hypotension
Figure 15-24
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Blood Pressure Regulation
PLAY Interactive Physiology® Animation: Cardiovascular System: Blood Pressure Regulation
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CVD: Risk Factors
• Not controllable• Sex• Age• Family history
• Controllable• Smoking• Obesity• Sedentary lifestyle• Untreated hypertension
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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
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LDL and Plaque
• The development of atherosclerotic plaques
Figure 15-25
(a) Normal arterial wall
(b) Fatty streak
(c) Stable fibrous plaque
(d) Vulnerable plaque
Endothelial cells Elastic connective tissue Smooth muscle cells
Macrophages
Smooth muscle cells
A lipid core accumulatesFibrous scar tissue
Smooth muscle cells
Calcifications are depositedwithin the plaque.
Platelets
Macrophages
LDL cholesterol accumulates
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LDL and Plaque
Figure 15-25a
(a) Normal arterial wall
Endothelial cells
Elastic connective tissue
Smooth muscle cells
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LDL and Plaque
Figure 15-25b
(b) Fatty streak
Macrophages
Smooth muscle cells
LDL cholesterol accumulates
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LDL and Plaque
Figure 15-25c
(c) Stable fibrous plaque
A lipid core accumulates
Fibrous scar tissue
Smooth muscle cells
Calcifications are depositedwithin the plaque.
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LDL and Plaque
Figure 15-25d
(d) Vulnerable plaque
Platelets
Macrophages
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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
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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
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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
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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