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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 © 2012 Pearson Education, Inc. Pressure and Resistance • Total capillary blood flow • Equals cardiac output • Is determined by • pressure and resistance in the cardiovascular system © 2012 Pearson Education, Inc. 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 © 2012 Pearson Education, Inc. Figure 21-10a Relationships among Vessel Diameter, Cross-Sectional Area, Blood Pressure, and Blood Velocity within the Systemic Circuit Vessel diameter (cm) Vessel diameter © 2012 Pearson Education, Inc. Figure 21-10b Relationships among Vessel Diameter, Cross-Sectional Area, Blood Pressure, and Blood Velocity within the Systemic Circuit Crosssectional area (cm2) Total cross-sectional area of vessels © 2012 Pearson Education, Inc. Figure 21-10c Relationships among Vessel Diameter, Cross-Sectional Area, Blood Pressure, and Blood Velocity within the Systemic Circuit Average blood pressure (mm Hg) Average blood pressure © 2012 Pearson Education, Inc. Figure 21-10d Relationships among Vessel Diameter, Cross-Sectional Area, Blood Pressure, and Blood Velocity within the Systemic Circuit Velocity of blood flow (cm/sec) Velocity of blood flow © 2012 Pearson Education, Inc. Figure 21-11 Pressures within the Systemic Circuit Systolic Pulse pressure Mean arterial pressure Diastolic mm Hg © 2012 Pearson Education, Inc. Pressure and Resistance • Capillary Pressures and Capillary Exchange • Vital to homeostasis • Moves materials across capillary walls by • Diffusion • Filtration • Reabsorption © 2012 Pearson Education, Inc. Pressure and Resistance • Diffusion • Movement of ions or molecules • From high concentration • To lower concentration • Along the concentration gradient © 2012 Pearson Education, Inc. 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 © 2012 Pearson Education, Inc. 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 © 2012 Pearson Education, Inc. Pressure and Resistance • Filtration • Driven by hydrostatic pressure • Water and small solutes forced through capillary wall • Leaves larger solutes in bloodstream © 2012 Pearson Education, Inc. 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 © 2012 Pearson Education, Inc. Figure 21-12 Capillary Filtration Capillary hydrostatic pressure (CHP) Amino acid Blood protein Glucose Ions Interstitial fluid Small solutes Hydrogen bond Water molecule Endothelial cell 1 © 2012 Pearson Education, Inc. Endothelial cell 2 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 © 2012 Pearson Education, Inc. 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 © 2012 Pearson Education, Inc. 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 © 2012 Pearson Education, Inc. 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 © 2012 Pearson Education, Inc. Pressure and Resistance • Net Filtration Pressure (NFP) • The difference between • Net hydrostatic pressure • And net osmotic pressure NFP = (CHP – IHP) – (BCOP – ICOP) © 2012 Pearson Education, Inc. Figure 21-13 Forces Acting across Capillary Walls KEY CHP (Capillary hydrostatic pressure) BCOP (Blood colloid osmotic pressure) Arteriole NFP (Net filtration pressure) Filtration 24 L/day 35 mm Hg 25 mm Hg NFP 10 mm Hg CHP BCOP Fluid forced out of capillary © 2012 Pearson Education, Inc. Venule Reabsorption No net fluid movement 25 mm Hg 20.4 L/day 18 25 mm mm Hg Hg 25 mm Hg NFP 0 NFP 7 mm Hg CHP BCOP No net movement of fluid BCOP CHP Fluid moves into capillary 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. HOMEOSTASIS RESTORED Local decrease in resistance and increase in blood flow HOMEOSTASIS Local vasodilators released Inadequate local blood pressure and blood flow HOMEOSTASIS DISTURBED • Physical stress (trauma, high temperature) • Chemical changes (decreased O2 or pH, increased CO2 or prostaglandins) • Increased tissue activity © 2012 Pearson Education, Inc. Normal blood pressure and volume Start 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. Neural mechanisms Stimulation of receptors sensitive to changes in systemic blood pressure or chemistry Stimulation of endocrine response Activation of cardiovascular centers Short-term elevation of blood pressure by sympathetic stimulation of the heart and peripheral vasoconstriction Long-term increase in blood volume and blood pressure Endocrine mechanisms If autoregulation is ineffective HOMEOSTASIS RESTORED © 2012 Pearson Education, Inc. Figure 21-15 Baroreceptor Reflexes of the Carotid and Aortic Sinuses Cardioinhibitory centers stimulated Cardioacceleratory centers inhibited Responses to Increased Baroreceptor Stimulation Decreased cardiac output Vasomotor centers inhibited Baroreceptors stimulated Vasodilation occurs HOMEOSTASIS DISTURBED HOMEOSTASIS RESTORED Rising blood pressure Blood pressure declines Start HOMEOSTASIS Normal range of blood pressure © 2012 Pearson Education, Inc. Figure 21-15 Baroreceptor Reflexes of the Carotid and Aortic Sinuses HOMEOSTASIS Start Normal range of blood pressure HOMEOSTASIS DISTURBED HOMEOSTASIS RESTORED Falling blood pressure Blood pressure rises Vasoconstriction occurs Baroreceptors inhibited Vasomotor centers stimulated Responses to Decreased Baroreceptor Stimulation Cardioacceleratory centers stimulated Cardioinhibitory centers inhibited © 2012 Pearson Education, Inc. Increased cardiac output Figure 21-16 The Chemoreceptor Reflexes Respiratory centers in the medulla oblongata stimulated Increasing CO2 levels, decreasing pH and O2 levels Effects on Cardiovascular Centers Reflex Response Chemoreceptors stimulated Respiratory Response Respiratory rate increases Cardiovascular Responses Cardioacceleratory centers stimulated Cardioinhibitory centers inhibited Vasomotor centers stimulated Start Vasoconstriction occurs HOMEOSTASIS DISTURBED HOMEOSTASIS RESTORED Elevated CO2 levels, decreased pH and O2 levels in blood and CSF Decreased CO2 levels, increased pH and O2 levels in blood and CSF HOMEOSTASIS Normal pH, O2, and CO2 levels in blood and CSF © 2012 Pearson Education, Inc. Increased cardiac output and blood pressure Figure 21-17a The Hormonal Regulation of Blood Pressure and Blood Volume HOMEOSTASIS HOMEOSTASIS DISTURBED Start Decreasing blood pressure and volume Normal blood pressure and volume Blood pressure and volume fall HOMEOSTASIS RESTORED Blood pressure and volume rise Short-term Long-term Sympathetic activation and release of adrenal hormones E and NE Endocrine Response of Kidneys Renin release leads to angiotensin II activation Erythropoietin (EPO) is released Increased cardiac output and peripheral vasoconstriction Angiotensin II Effects Antidiuretic hormone released Aldosterone secreted Factors that compensate for decreased blood pressure and volume © 2012 Pearson Education, Inc. Thirst stimulated Increased red blood cell formation Combined Short-Term and Long-Term Effects Increased blood pressure Increased blood volume Figure 21-17b The Hormonal Regulation of Blood Pressure and Blood Volume Responses to ANP and BNP Increased Na loss in urine Increased water loss in urine Natriuretic peptides released by the heart Reduced thirst Combined Effects Inhibition of ADH, aldosterone, epinephrine, and norepinephrine release Reduced blood volume Peripheral vasodilation HOMEOSTASIS DISTURBED HOMEOSTASIS RESTORED Rising blood pressure and volume Declining blood pressure and volume Increasing blood pressure and volume Factors that compensate for increased blood pressure and volume © 2012 Pearson Education, Inc. HOMEOSTASIS Normal blood pressure and volume Table 21-2 Changes in Blood Distribution during Exercise © 2012 Pearson Education, Inc. 21-4 Cardiovascular Adaptation Table 21-3 Effects of Training on Cardiovascular Performance Subject Heart Weight (g) Stroke Volume (mL) Heart Rate (BPM) Cardiac Blood Pressure Output (systolic/ (L/min) diastolic) Nonathlete (rest) 300 60 83 5.0 120/80 104 192 19.9 187/75 100 53 5.3 120/80 167 182 30.4 200/90* Nonathlete (maximum) Trained athlete (rest) Trained athlete (maximum) 500 *Diastolic pressures of athletes during maximum activity have not been accurately measured. © 2012 Pearson Education, Inc. Figure 21-18 Cardiovascular Responses to Hemorrhaging and Blood Loss HOMEOSTASIS Normal blood pressure and volume HOMEOSTASIS DISTURBED Blood pressure and volume rise Extensive bleeding reduces blood pressure and volume Falling blood pressure and volume Elevation of blood volume Responses coordinated by the endocrine system Responses directed by the nervous system Pain, stress, anxiety, fear Long-Term Hormonal Response Cardiovascular Responses ADH, angiotensin II, aldosterone, and EPO released Peripheral vasoconstriction; mobilization of venous reserve Stimulation of baroreceptors and chemoreceptors Higher Centers Stimulation of cardiovascular centers © 2012 Pearson Education, Inc. HOMEOSTASIS RESTORED General sympathetic activation Increased cardiac output