© 2012 pearson education, inc. figure 21-8 an overview of cardiovascular physiology cardiac output...
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© 2012 Pearson Education, Inc.
Figure 21-8 An Overview of Cardiovascular Physiology
Cardiac Output
Venous Return
Regulation(Neural and Hormonal)
VenousPressure
Arterial BloodPressure
PeripheralResistance
Capillary Pressure
Capillary exchange
Interstitial fluid
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Pressure and Resistance
• Total capillary blood flow
• Equals cardiac output
• Is determined by
• pressure and resistance in the cardiovascular
system
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Pressure and Resistance
• An Overview of Cardiovascular Pressures
• 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
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Figure 21-10a Relationships among Vessel Diameter, Cross-Sectional Area, Blood Pressure, and Blood Velocity within the Systemic Circuit
Vesseldiameter
(cm)
Vessel diameter
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Figure 21-10b Relationships among Vessel Diameter, Cross-Sectional Area, Blood Pressure, and Blood Velocity within the Systemic Circuit
Total cross-sectional area of vessels
Cross-sectional
area(cm2)
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Figure 21-10c Relationships among Vessel Diameter, Cross-Sectional Area, Blood Pressure, and Blood Velocity within the Systemic Circuit
Average blood pressure
Averageblood
pressure(mm Hg)
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Figure 21-10d Relationships among Vessel Diameter, Cross-Sectional Area, Blood Pressure, and Blood Velocity within the Systemic Circuit
Velocity of blood flow
Velocityof blood
flow(cm/sec)
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Figure 21-11 Pressures within the Systemic Circuit
Systolic
Pulsepressure
Diastolic
mm Hg
Mean arterialpressure
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Pressure and Resistance
• Capillary Pressures and Capillary Exchange
• Vital to homeostasis
• Moves materials across capillary walls by
• Diffusion
• Filtration
• Reabsorption
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Pressure and Resistance
• Diffusion
• Movement of ions or molecules
• From high concentration
• To lower concentration
• Along the concentration gradient
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Pressure and Resistance
• Diffusion Routes
• Water, ions, and small molecules such as glucose
• Diffuse between adjacent endothelial cells
• Or through fenestrated capillaries
• Some ions (Na+, K+, Ca2+, Cl-)
• Diffuse through channels in plasma membranes
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Pressure and Resistance
• Diffusion Routes
• Large, water-soluble compounds
• Pass through fenestrated capillaries
• Lipids and lipid-soluble materials such as O2 and
CO2
• Diffuse through endothelial plasma membranes
• Plasma proteins
• Cross endothelial lining in sinusoids
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Pressure and Resistance
• Filtration
• Driven by hydrostatic pressure
• Water and small solutes forced through capillary wall
• Leaves larger solutes in bloodstream
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Pressure and Resistance
• Reabsorption
• The result of osmosis
• Blood colloid osmotic pressure
• Equals pressure required to prevent osmosis
• Caused by suspended blood proteins that are too large to
cross capillary walls
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Figure 21-12 Capillary Filtration
Capillaryhydrostatic
pressure(CHP) Amino acid
Blood protein
Glucose
Ions
Interstitialfluid
Hydrogenbond
Watermolecule
Small solutes
Endothelialcell 2
Endothelialcell 1
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Pressure and Resistance
• 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
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Pressure and Resistance
• Interplay between Filtration and Reabsorption
• Hydrostatic pressure
• Forces water out of solution
• Osmotic pressure
• Forces water into solution
• Both control filtration and reabsorption through
capillaries
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Pressure and Resistance
• Net Hydrostatic Pressure
• Is the difference between
• Capillary hydrostatic pressure (CHP)
• And interstitial fluid hydrostatic pressure (IHP)
• Pushes water and solutes
• Out of capillaries
• Into interstitial fluid
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Pressure and Resistance
• Net Colloid Osmotic Pressure
• Is 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
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Pressure and Resistance
• Net Filtration Pressure (NFP)
• The difference between
• Net hydrostatic pressure
• And net osmotic pressure
NFP = (CHP – IHP) – (BCOP – ICOP)
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Figure 21-13 Forces Acting across Capillary Walls
KEY
Arteriole
Filtration
CHP (Capillaryhydrostatic pressure)
Venule
BCOP (Blood colloidosmotic pressure)
NFP (Net filtrationpressure)
24 L/day 20.4 L/dayNo net fluidmovement
Reabsorption
35mmHg
25mmHg
25mmHg
25mmHg
25mmHg
18mmHg
NFP 10 mm Hg NFP 0 NFP 7 mm Hg
CHP BCOPFluid forced
out of capillary
CHP BCOPNo net
movementof fluid
BCOP CHPFluid movesinto capillary
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Figure 21-14 Short-Term and Long-Term Cardiovascular Responses
Autoregulation
Local vasodilatorsreleased
HOMEOSTASISRESTORED
HOMEOSTASIS DISTURBED
HOMEOSTASIS
Local decreasein resistanceand increase inblood flow
Inadequatelocal bloodpressure andblood flow
Normalblood pressure
and volume
• Physical stress (trauma, high temperature)• Chemical changes (decreased O2 or pH, increased CO2 or prostaglandins)• Increased tissue activity
Autoregulation is dueto opening and closing precapillary sphinctersdue to local release ofvasodilator or vasoconstrictorchemicals from the tissue.
Start
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Figure 21-14 Short-Term and Long-Term Cardiovascular Responses
Central Regulation
Stimulation ofreceptors sensitiveto changes insystemic bloodpressure orchemistry
Endocrine mechanisms
HOMEOSTASISRESTORED
Neuralmechanisms
Activation ofcardiovascularcenters
Stimulationof endocrineresponse
Long-term increasein blood volumeand blood pressure
Short-term elevation of blood pressure bysympatheticstimulation of theheart and peripheralvasoconstriction
Central regulation involves neuroendocrine mechanisms that control the total systemic circulation. This regulation involves both the cardiovascular centers and the vasomotor centers.
If autoregulation is ineffective
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Figure 21-15 Baroreceptor Reflexes of the Carotid and Aortic Sinuses
Responses to IncreasedBaroreceptor Stimulation
Baroreceptorsstimulated
HOMEOSTASISDISTURBED
Rising bloodpressure
Cardioinhibitorycenters stimulated
Cardioacceleratorycenters inhibited
Vasomotor centersinhibited
Decreasedcardiacoutput
Vasodilationoccurs
HOMEOSTASISRESTORED
Blood pressuredeclines
HOMEOSTASIS
Normal rangeof bloodpressure
Start
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Figure 21-15 Baroreceptor Reflexes of the Carotid and Aortic Sinuses
HOMEOSTASIS
Normal rangeof bloodpressure
HOMEOSTASISDISTURBED
HOMEOSTASISRESTORED
Falling bloodpressure
Blood pressurerises
Baroreceptorsinhibited
Vasoconstrictionoccurs
Increasedcardiacoutput
Vasomotor centersstimulated
Cardioacceleratorycenters stimulated
Cardioinhibitorycenters inhibited
Responses to DecreasedBaroreceptor Stimulation
Start
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Figure 21-16 The Chemoreceptor Reflexes
Increasing CO2 levels,
decreasing pHand O2 levels
Respiratory centers inthe medulla oblongatastimulated
Respiratory rateincreases
Increased cardiacoutput and bloodpressure
Cardioacceleratorycenters stimulated
Cardioinhibitorycenters inhibited
Respiratory Response
CardiovascularResponses
Effects onCardiovascular Centers
Vasomotor centersstimulated
Vasoconstrictionoccurs
Normal pH, O2,
and CO2 levels in
blood and CSF
HOMEOSTASIS
Elevated CO2 levels,
decreased pH and O2
levels in blood and CSF
HOMEOSTASISDISTURBED
Start
Decreased CO2 levels,
increased pH and O2
levels in blood and CSF
HOMEOSTASISRESTORED
Reflex Response
Chemoreceptorsstimulated
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Figure 21-17a The Hormonal Regulation of Blood Pressure and Blood Volume
HOMEOSTASIS
Factors that compensate fordecreased blood pressure andvolume
Increased red bloodcell formation
Thirst stimulated
Antidiuretic hormonereleased
Angiotensin II Effects
Combined Short-Termand Long-Term Effects
Endocrine Responseof Kidneys
Renin release leadsto angiotensin IIactivation
Erythropoietin (EPO)is released
Increased cardiacoutput andperipheralvasoconstriction
Sympathetic activationand release of adrenalhormones E and NE
Long-term
Short-term
Increasedbloodpressure
Increasedbloodvolume
Decreasing bloodpressure and
volume
StartBlood pressureand volume fall
HOMEOSTASISDISTURBED HOMEOSTASIS
RESTORED
Normal bloodpressure and
volume
Blood pressureand volume rise
Aldosterone secreted
Angiotensin II
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Figure 21-17b The Hormonal Regulation of Blood Pressure and Blood Volume
HOMEOSTASIS
Factors that compensate forincreased blood pressure andvolume
Increasing bloodpressure and
volume
HOMEOSTASISRESTORED
Declining bloodpressure and
volume
Normalblood pressure
and volume
HOMEOSTASISDISTURBED
Rising bloodpressure and
volume
Natriureticpeptides releasedby the heart
Increased water loss inurine
Reduced thirst
Inhibition of ADH,aldosterone, epinephrine,and norepinephrinerelease
Peripheral vasodilation
Reduced bloodvolume
CombinedEffects
Increased Na loss inurine
Responses to ANPand BNP
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Table 21-2 Changes in Blood Distribution during Exercise
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21-4 Cardiovascular Adaptation
Table 21-3 Effects of Training on Cardiovascular Performance
Subject Heart Weight (g)
Stroke Volume (mL)
Heart Rate (BPM)
Cardiac Output (L/min)
Blood Pressure (systolic/ diastolic)
Nonathlete (rest) 300 60 83 5.0 120/80
Nonathlete (maximum)
104 192 19.9 187/75
Trained athlete (rest)
500 100 53 5.3 120/80
Trained athlete (maximum)
167 182 30.4 200/90*
*Diastolic pressures of athletes during maximum activity have not been accurately measured.
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Figure 21-18 Cardiovascular Responses to Hemorrhaging and Blood Loss
Normal bloodpressure and
volume
Extensive bleedingreduces bloodpressure andvolume
HOMEOSTASISDISTURBED
Responsescoordinated by theendocrine system
Responsesdirected by thenervous system
Falling bloodpressure and
volume
Long-Term Hormonal Response
ADH, angiotensin II, aldosterone,and EPO released
Blood pressureand volume rise
HOMEOSTASISRESTORED
Cardiovascular Responses
Peripheralvasoconstriction;mobilization ofvenous reserve
Increasedcardiacoutput
Elevationof bloodvolume
Stimulation ofbaroreceptors andchemoreceptorsPain, stress,
anxiety, fear
Higher Centers
Stimulation ofcardiovascularcenters
Generalsympatheticactivation
HOMEOSTASIS