blood flow and the control of blood pressure
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Blood Flow and the Control of Blood Pressure. 15. Overview: Cardiovascular System. Arteries take blood away from the heart and veins return it. Arteries connect to arterioles, that connect to capillaries, that connect to venules, that connect to veins - PowerPoint PPT PresentationTRANSCRIPT
POWERPOINT® LECTURE SLIDE PRESENTATIONby LYNN CIALDELLA, MA, MBA, The University of Texas at AustinAdditional Text by J Padilla Exclusively for physiology at ECC
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
HUMAN PHYSIOLOGYAN INTEGRATED APPROACH FOURTH EDITION
DEE UNGLAUB SILVERTHORN
UNIT 3UNIT 3
PART A
15 Blood Flow and the Control of Blood Pressure
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Overview: Cardiovascular System
Figure 14-1
Arteries take blood away from the heart and veins return it.
Arteries connect to arterioles, that connect to capillaries, that connect to venules, that connect to veins
Two portal systems shown here have two sets of capillaries connected
Arteries take blood away from the heart and veins return it.
Arteries connect to arterioles, that connect to capillaries, that connect to venules, that connect to veins
Two portal systems shown here have two sets of capillaries connected
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Functional Model of the Cardiovascular System
Figure 15-1
Systemic Arteries maintain pressure during ventricular relaxation by changing vessel diameter
Arteries and veins are for travel and capillaries for exchange
Systemic Arteries maintain pressure during ventricular relaxation by changing vessel diameter
Arteries and veins are for travel and capillaries for exchange
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 15-2
Blood Vessel Structure
Blood vessels vary in diameter and wall thickness.
Veins have a larger diameter and thinner walls than arteries.
Capillaries are thin enough to allow for diffusion and narrow to restrict RBC to flow in single file
Blood vessels vary in diameter and wall thickness.
Veins have a larger diameter and thinner walls than arteries.
Capillaries are thin enough to allow for diffusion and narrow to restrict RBC to flow in single file
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 15-3
Metarterioles
Capillaries lack smooth muscle and elastic tissue reinforcement which facilitates exchange
The walls are thin enough to allow WBC and plasma to scape. Plasma that leaves the capillaries and bathes the tissues will be called lymph and will be collected by lymphatic capillaries.
The walls are thin enough to allow WBC and plasma to scape. Plasma that leaves the capillaries and bathes the tissues will be called lymph and will be collected by lymphatic capillaries.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 15-15a
Precapillary Sphincters
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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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Continous Capillary Fenestrated Capillary
Sinusoidal Capillary
Two Types of CapillariesTwo Types of Capillaries
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Angiogenesis
New blood vessel development- after birth, happens to accommodate tissue growth like when one gains weight
Necessary for normal development- growth needed during childhood
Wound healing and uterine lining growth- blood vessel formation needed in adulhood
Controlled by cytokines- chemical signal that induce mitosis Mitogens: VEGF and FGF- vascular endothelial growth factor
and fibroblast growth factor
Inhibit: angiostatin and endostatin- these natural occuring chemicals are being used to treat cancer and coronary disease
Coronary heart disease Collateral circulation- natural formation of additional blood
vessels to supplement flow of blocked vessels
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 15-17
Velocity of Blood Flow
Velocity of flow depends on total cross-sectional area of the vessels. The greater the total cross-sectional area the slower the velocity. Velocity is slowest at the capillaries. Although the diameter of a capillary is smaller than any other vessel its total cross-sectional area is greater than any other.
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Review of Blood Flow
Flow is inversely proportional to resistance. Resistance is influenced by vessel diameter. The larger the diameter the slower the speed as long as the flow rate is constant.
Flow is inversely proportional to resistance. Resistance is influenced by vessel diameter. The larger the diameter the slower the speed as long as the flow rate is constant.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 14-3a
Pressure Differences in Static and Flowing Fluids
Pressure falls over distance as energy is lost because of friction. In circulation the further away the blood is from the heart the lower the pressure. Pressure is lower is veins than in arteries
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 14-4
Fluid Flow through a Tube
Flow ∆P
Pressure gradient cause a fluid to flow . Blood vessels create pressure gradients by altering diameter size
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The Role of Radius in Determining Resistance to Flow
A small change in diameter can use a great change in resistance and flow. Thus blood vessels can dramatically alter blood flow when they vasoconstrict or vasodialate
A small change in diameter can use a great change in resistance and flow. Thus blood vessels can dramatically alter blood flow when they vasoconstrict or vasodialate
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 14-6
Fluid Rate Versus Velocity of Flow
The velocity of flow is influenced by cross-sectional area. Although a large cross-sectional area may allow more fluid to pass at one time, it also causes it to slow down. Don’t think of cross-sectional area as the diameter of the blood vessel.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 15-5
Pressure throughout the Systemic CirculationBlood pressure is highest in the arteries and decreases continuously as it flows through the circulatory system.
Systolic pressure is exerted on vessel walls when the heart contracts
Diastolic pressure is pressure during heart relaxation.
Pulse pressure measures strength of pressure wave systolic P – diastolic P
Mean arterial pressure measures driving pressure diastole P + 1/3 pulse pressure.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 15-4a
Elastic Recoil in Arteries
(a) Ventricular contraction
Ventricle contracts.
Aorta and arteries expand and store pressure in elastic walls.
Semilunar valve opens.
Arterioles1
1 2
2
3
3
This process explains how pressure is transferred to blood vessels when the heart contracts
This process explains how pressure is transferred to blood vessels when the heart contracts
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Elastic Recoil in Arteries
(b) Ventricular relaxation
Isovolumic ventricularrelaxation occurs.
Elastic recoil of arteries sends blood forward into rest of circulatory system.
Semilunar valve shuts, preventing flow back into ventricle.
1
2
3
3
21
This process explains how pressure is maintained in blood vessels while the heart relaxes
This process explains how pressure is maintained in blood vessels while the heart relaxes
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 15-7
Measurement of Arterial Blood PressurePulse Pressure = systolic P – diastolic PValves ensure one-way flow in veinsMAP = diastolic P + 1/3(systolic P – diastolic P)
Pulse Pressure = systolic P – diastolic PValves ensure one-way flow in veinsMAP = diastolic P + 1/3(systolic P – diastolic P)
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Pressure Change Pressure created by contracting muscles of the heart and blood
vessels is transferred to blood Driving pressure is created by the ventricle. Thus usually
blood pressure reading focus on left ventricular systole and diastole and arterial pressure not venous pressure.
If blood vessels constrict, blood pressure increases because the diameter decreases and the muscle exerts more pressure on the blood.
If blood vessels dilate, blood pressure decreases because the opposite happens.
Blood volume changes are major factors for blood pressure in CVS. Drinking a lot of fluid increases blood volume, blood loss and dehydration decreases blood volume. The kidneys try to regulate blood volume via fluid loss or retention. The CV system cause changes in diameter to help compensate when posible.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 15-9
Blood Pressure
Blood pressure control involves both the cardiovascular system and the renal system
Increase or decrease in blood volume is compensated by CV and kidney changes
Increase or decrease in blood volume is compensated by CV and kidney changes
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Stroke Volume and Cardiac Output Stroke volume
Amount of blood expelled by one ventricle during a contraction EDV – ESV = stroke volume
Force of contraction Stroke volume increases of decreases based on contraction force Affected by length of muscle fiber and contractility of heart
Frank-Starling law Stroke volume increase as EDV increases
EDV determined by venous return Skeletal muscle pump Respiratory pump Sympathetic innervation
Cardiac output Volume of blood pumped by one ventricle in a given period of time CO = HR SV (heart rate times stroke volume) Average = 5 L/min
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Factors that Affect Cardiac Output
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Blood Pressure
Mean arterial pressure is a function of cardiac output and resistance in the arterioles= the volume produced by the heart times vessel radius (vasodilation/vasoconstriction)
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Arteriolar Resistance (vasoconstriction) Sympathetic reflexes- control blood distribution as needed to maintian
homeostasis such as body temperature Local control of arteriolar resistance- based on metabolism of tissue and tissue
needs for blood flow, can override CNS control in heart and muscle Hormones- those that bind to kidney cells and control salt and water levels. Myogenic autoregulation- increased blood flow causes increase pressure that
stretches the walls. The smooth muscle responds by contracting thus increasing resistance and reducing flow. Therefore, no neural input is needed
Paracrines –secreted by endothelium, allows for local control Active hyperemia- increase blood flow accompanies increased metabolic
activity. As more paracrines accumulate, they call for more blood. Reactive hyperemia- increase blood flow after a state of abnormally low
metabolic rate due local hypoxia. Nitric oxide is made for vasodilation Sympathetic control
SNS: norepinephrine; tonic release maintains myogenic tone, increase release causes vasoconstriction
Adrenal medulla: epinephrine: heart, liver, and skeletal muscle vasodilate
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Hyperemia
Figure 15-11a
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Norepinephrine
Tonic control of arteriolar diameter
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Factors that Influence Mean Arterial Pressure
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 15-21
Blood Pressure
Medullary cardiovascular
control center
Carotid and aorticbaroreceptors
Change in blood
pressure
Integrating center
Stimulus
Efferent pathway
Effector
Sensor/receptor
KEY
Components of the baroreceptor reflexComponents of the baroreceptor reflex
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 15-21 (5 of 10)
Blood Pressure
Medullary cardiovascular
control center
Carotid and aorticbaroreceptors
Change in blood
pressure
Parasympatheticneurons
Sympatheticneurons
Integrating center
Stimulus
Efferent pathway
Effector
Sensor/receptor
KEY
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 15-21 (8 of 10)
Blood Pressure
Medullary cardiovascular
control center
Carotid and aorticbaroreceptors
Change in blood
pressure
Parasympatheticneurons
Sympatheticneurons
Ventricles
SA node
Integrating center
Stimulus
Efferent pathway
Effector
Sensor/receptor
KEY
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 15-21 (10 of 10)
Blood Pressure
Medullary cardiovascular
control center
Carotid and aorticbaroreceptors
Change in blood
pressure
Parasympatheticneurons
Sympatheticneurons
Veins
Arterioles
Ventricles
SA node
Integrating center
Stimulus
Efferent pathway
Effector
Sensor/receptor
KEY
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 15-22
Blood Pressure
The baroreceptor reflex: the response to increased blood pressure
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 15-23
Blood Pressure
The baroreceptor reflex: the response to orthostatic hypotension
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Distribution of Blood
Distribution of blood in the body at rest
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Cardiovascular disease (CVD): Risk Factors Risk factors that are not controllable
Gender Age Family History
Risk factors that are controllable Smoking Obesity Sedentary lifestyle Untreated hypertension
Uncontrollable genetic but modifiable lifestyle Blood lipids
Leads to atherosclerosis HDL-C versus LDL-C
Diabetes mellitus Metabolic disorder contributes to development of atherosclerosis
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 15-24
LDL and Plaque
The development of atherosclerotic plaques
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 15-25
Hypertension
Graph shows the relationship between blood pressure and the risk of developing cardiovascular disease
Essential hypertension has no clear cause other than hereditary
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