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Figure 21-8 An Overview of Cardiovascular Physiology

Figure 21-8 An Overview of Cardiovascular Physiology. Cardiac Output. Venous Return. Arterial Blood Pressure. Regulation (Neural and Hormonal). Venous Pressure. Peripheral Resistance. Capillary Pressure. Capillary exchange. Interstitial fluid. Pressure and Resistance.

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Figure 21-8 An Overview of Cardiovascular Physiology

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  1. Figure 21-8 An Overview of Cardiovascular Physiology Cardiac Output Venous Return Arterial BloodPressure Regulation(Neural and Hormonal) VenousPressure PeripheralResistance Capillary Pressure Capillary exchange Interstitial fluid

  2. Pressure and Resistance • Total capillary blood flow • Equals cardiac output • Is determined by • pressure and resistance in the cardiovascular system

  3. 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

  4. Figure 21-10a Relationships among Vessel Diameter, Cross-Sectional Area, Blood Pressure, and Blood Velocity within the Systemic Circuit Vesseldiameter (cm) Vessel diameter

  5. Figure 21-10b Relationships among Vessel Diameter, Cross-Sectional Area, Blood Pressure, and Blood Velocity within the Systemic Circuit Cross-sectionalarea(cm2) Total cross-sectional area of vessels

  6. Figure 21-10c Relationships among Vessel Diameter, Cross-Sectional Area, Blood Pressure, and Blood Velocity within the Systemic Circuit Averagebloodpressure(mm Hg) Average blood pressure

  7. Figure 21-10d Relationships among Vessel Diameter, Cross-Sectional Area, Blood Pressure, and Blood Velocity within the Systemic Circuit Velocityof bloodflow(cm/sec) Velocity of blood flow

  8. Figure 21-11 Pressures within the Systemic Circuit Systolic Pulsepressure Mean arterialpressure Diastolic mm Hg

  9. Pressure and Resistance • Capillary Pressures and Capillary Exchange • Vital to homeostasis • Moves materials across capillary walls by • Diffusion • Filtration • Reabsorption

  10. Pressure and Resistance • Diffusion • Movement of ions or molecules • From high concentration • To lower concentration • Along the concentration gradient

  11. 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

  12. 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

  13. Pressure and Resistance • Filtration • Driven by hydrostatic pressure • Water and small solutes forced through capillary wall • Leaves larger solutes in bloodstream

  14. 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

  15. Figure 21-12 Capillary Filtration Capillaryhydrostaticpressure(CHP) Amino acid Blood protein Glucose Ions Interstitialfluid Small solutes Hydrogenbond Watermolecule Endothelialcell 2 Endothelialcell 1

  16. 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

  17. 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

  18. 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

  19. 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

  20. Pressure and Resistance • Net Filtration Pressure (NFP) • The difference between • Net hydrostatic pressure • And net osmotic pressure NFP = (CHP – IHP) – (BCOP – ICOP)

  21. Figure 21-13 Forces Acting across Capillary Walls KEY CHP (Capillaryhydrostatic pressure) BCOP (Blood colloidosmotic pressure) Arteriole NFP (Net filtrationpressure) Venule Filtration Reabsorption No net fluidmovement 20.4 L/day 24 L/day 18mmHg 25mmHg 35mmHg 25mmHg 25mmHg 25mmHg NFP  0 NFP 7 mm Hg NFP 10 mm Hg CHP  BCOPFluid forced out of capillary CHP  BCOPNo netmovementof fluid BCOP  CHPFluid moves into capillary

  22. Figure 21-14 Short-Term and Long-Term Cardiovascular Responses Autoregulation Autoregulation is due to opening and closing precapillary sphincters due to local release of vasodilator or vasoconstrictor chemicals from the tissue. HOMEOSTASISRESTORED Local decreasein resistanceand increase inblood flow HOMEOSTASIS Normalblood pressureand volume Local vasodilatorsreleased Inadequatelocal bloodpressure andblood flow HOMEOSTASIS DISTURBED • Physical stress (trauma, high temperature)• Chemical changes (decreased O2 or pH, increased CO2 or prostaglandins)• Increased tissue activity Start

  23. Figure 21-14 Short-Term and Long-Term Cardiovascular Responses Central Regulation Central regulation involves neuroendocrine mechanisms that control the total systemic circulation. This regulation involves both the cardiovascular centers and the vasomotor centers. Short-term elevation of blood pressure bysympatheticstimulation of theheart and peripheralvasoconstriction Stimulation ofreceptors sensitiveto changes insystemic bloodpressure orchemistry Activation ofcardiovascularcenters Neuralmechanisms Stimulationof endocrineresponse Long-term increasein blood volumeand blood pressure Endocrine mechanisms If autoregulation is ineffective HOMEOSTASISRESTORED

  24. Figure 21-15 Baroreceptor Reflexes of the Carotid and Aortic Sinuses Cardioinhibitorycenters stimulated Cardioacceleratorycenters inhibited Decreasedcardiacoutput Responses to IncreasedBaroreceptor Stimulation Vasomotor centersinhibited Baroreceptorsstimulated Vasodilationoccurs HOMEOSTASISRESTORED HOMEOSTASISDISTURBED Blood pressuredeclines Rising bloodpressure Start HOMEOSTASIS Normal rangeof bloodpressure

  25. Figure 21-15 Baroreceptor Reflexes of the Carotid and Aortic Sinuses HOMEOSTASIS Normal rangeof bloodpressure Start HOMEOSTASISRESTORED HOMEOSTASISDISTURBED Falling bloodpressure Blood pressurerises Vasoconstrictionoccurs Baroreceptorsinhibited Vasomotor centersstimulated Increasedcardiacoutput Responses to DecreasedBaroreceptor Stimulation Cardioacceleratorycenters stimulated Cardioinhibitorycenters inhibited

  26. Figure 21-16 The Chemoreceptor Reflexes Respiratory Response Respiratory centers inthe medulla oblongatastimulated Respiratory rateincreases Increasing CO2 levels,decreasing pHand O2 levels CardiovascularResponses Effects onCardiovascular Centers Cardioacceleratorycenters stimulated Reflex Response Increased cardiacoutput and bloodpressure Chemoreceptorsstimulated Cardioinhibitorycenters inhibited Vasomotor centersstimulated Vasoconstrictionoccurs HOMEOSTASISRESTORED HOMEOSTASISDISTURBED Start Elevated CO2 levels,decreased pH and O2levels in blood and CSF Decreased CO2 levels,increased pH and O2levels in blood and CSF HOMEOSTASIS Normal pH, O2,and CO2 levels inblood and CSF

  27. Figure 21-17a The Hormonal Regulation of Blood Pressure and Blood Volume HOMEOSTASIS Normal bloodpressure andvolume HOMEOSTASISDISTURBED HOMEOSTASISRESTORED Start Blood pressureand volume fall Blood pressureand volume rise Decreasing bloodpressure andvolume Short-term Long-term Combined Short-Termand Long-Term Effects Sympathetic activationand release of adrenalhormones E and NE Increasedbloodpressure Increasedbloodvolume Endocrine Responseof Kidneys Increased cardiacoutput andperipheralvasoconstriction Renin release leadsto angiotensin IIactivation Angiotensin II Effects Erythropoietin (EPO)is released Angiotensin II Antidiuretic hormonereleased Aldosterone secreted Factors that compensate fordecreased blood pressure andvolume Thirst stimulated Increased red bloodcell formation

  28. Figure 21-17b The Hormonal Regulation of Blood Pressure and Blood Volume Responses to ANPand BNP Increased Na loss inurine Increased water loss inurine CombinedEffects Reduced thirst Natriureticpeptides releasedby the heart Inhibition of ADH,aldosterone, epinephrine,and norepinephrinerelease Reduced bloodvolume Peripheral vasodilation HOMEOSTASISRESTORED HOMEOSTASISDISTURBED Declining bloodpressure andvolume Rising bloodpressure andvolume HOMEOSTASIS Increasing bloodpressure andvolume Normalblood pressureand volume Factors that compensate forincreased blood pressure andvolume

  29. Table 21-2 Changes in Blood Distribution during Exercise

  30. 21-4 Cardiovascular Adaptation *Diastolic pressures of athletes during maximum activity have not been accurately measured.

  31. Figure 21-18 Cardiovascular Responses to Hemorrhaging and Blood Loss HOMEOSTASIS Normal bloodpressure andvolume HOMEOSTASISRESTORED HOMEOSTASISDISTURBED Blood pressureand volume rise Extensive bleedingreduces bloodpressure andvolume Elevationof bloodvolume Falling bloodpressure andvolume Responsescoordinated by theendocrine system Responsesdirected by thenervous system Cardiovascular Responses Long-Term Hormonal Response ADH, angiotensin II, aldosterone,and EPO released Increasedcardiacoutput Peripheralvasoconstriction;mobilization ofvenous reserve Stimulation ofbaroreceptors andchemoreceptors Pain, stress,anxiety, fear Higher Centers Generalsympatheticactivation Stimulation ofcardiovascularcenters

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