Blood Vessels and Circulation Chapter 21 C h a p t e r 21 Blood Vessels and Circulation

Pressure and Resistance Total capillary blood flow directly related to cardiac output Is determined by: pressure and resistance in the cardiovascular system Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Pressure and Resistance Figure 21–8 An Overview of Cardiovascular Physiology Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Pressure and Resistance Pressure (P) The heart generates P to overcome resistance (R) Absolute pressure less important than pressure gradient The Pressure Gradient (P) is the difference in P’s Circulatory pressure has pressure gradient It is the difference between: Pressure at the heart Pressure at peripheral capillary beds Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Pressure and Resistance Flow (F) Is proportional to the pressure gradient (P) divided by R F= P / R Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Pressure and Resistance Measuring Pressure Blood pressure (BP) Arterial pressure (mm Hg) Capillary hydrostatic pressure (CHP) Pressure within the capillary beds Venous pressure Pressure in the venous system Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Pressure and Resistance Circulatory Pressure: ∆P across the systemic circuit (about 100 mm Hg) Circulatory pressure must overcome total peripheral R R of entire cardiovascular system Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Pressure and Resistance Total Peripheral “R” affected by 3 factors: Vascular R Due to friction between blood and vessel walls Depends on vessel length and vessel diameter: adult vessel length is constant vessel diameter varies by vasodilation/vasoconstriction... (R increases exponentially as vessel diameter ________) Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Pressure and Resistance Viscosity R caused by molecules and suspended materials in a liquid Whole blood viscosity is about 4 x water Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Pressure and Resistance Turbulence Swirling action that disturbs smooth flow of liquid Occurs in heart chambers and great vessels Atherosclerotic plaques cause abnormal turbulence Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Pressure and Resistance Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Pressure and Resistance Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Pressure and Resistance 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 Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Pressure and Resistance Normal/Average BP= 120/80 Abnormal BP: Hypertension - Abnormally high BP greater than 140/90 Hypotension - Abnormally low BP Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Pressure and Resistance Larger arterial walls have elastic rebound Stretch during systole Recoil to original shape during diastole Keep blood moving during diastole Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Pressure and Resistance Figure 21–9 Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Pressure and Resistance Pressures in Small Arteries and Arterioles affected by distance MAP and pulse pressure decrease with distance from heart Blood pressure decreases as multiple branches arise Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Pressure and Resistance Figure 21–10 Pressures within the Systemic Circuit Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Pressure and Resistance Venous Pressure and Venous Return Low pressure exists in venous system 2 actions improve venous return: Muscular compression of peripheral veins: compression of skeletal muscles pushes blood toward heart (through one-way valves) The respiratory pump in thoracic cavity: inhaling decreases thoracic pressure (draws air/blood toward lungs) exhaling raises thoracic pressure (forces air/blood away from lungs) Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Pressure and Resistance Capillary Pressures and Exchange Vital to homeostasis Moves materials across capillary walls by Diffusion (from concentration gradient) Filtration (from hydrostatic pressure) Reabsorption (from osmosis) Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Pressure and Resistance Figure 21–11 Capillary Filtration Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Pressure and Resistance Interplay between Filtration and Reabsorption: Hydrostatic pressure Forces water out of solution Osmotic pressure Pulls water into solution Both control filtration and reabsorption through capillaries Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Pressure and Resistance Net Hydrostatic Pressure: Is the difference between Capillary hydrostatic pressure (CHP) And Interstitial fluid hydrostatic pressure (IHP) Pushes water and solutes... From __________ to ____________ Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

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… From __________ into ____________ Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Pressure and Resistance Net Filtration Pressure (NFP): The difference between: Net Hydrostatic pressure And Net Osmotic pressure NFP = (CHP – IHP) – (BCOP – ICOP) Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Pressure and Resistance Capillary Exchange At arterial end of capillary Fluid moves from capillary Into interstitial fluid At venous end of capillary Fluid moves into capillary From interstitial fluid Transition point between filtration and reabsorption Is closer to venous end than arterial end So… capillaries usually filter more than they reabsorb Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Pressure and Resistance Figure 21–12 Forces Acting across Capillary Walls Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Pressure and Resistance Water continuously moves out of capillaries and back into the bloodstream (Fluid Recycling ) via the lymphatic system Ensures constant plasma and interstitial fluid communication Accelerates distribution of nutrients, hormones, and dissolved gases through tissues Transports insoluble lipids and tissue proteins that cannot cross capillary walls Flushes bacterial toxins and chemicals to immune system tissues Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Pressure and Resistance Capillary Dynamics Hemorrhaging Reduces CHP and NFP Increase _____________of interstitial fluid (recall of fluids) Dehydration Increases BCOP Increases _____________ of interstitial fluid High BP Elevated CHP Increases _____________ into the interstitial fluid Fluid builds up in peripheral tissues (Edema) Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiovascular Regulation Tissue Perfusion is the blood flow through tissues Carries O2 and nutrients to tissues and organs Carries CO2 and wastes away Is affected by Cardiac output Peripheral resistance Blood Pressure Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiovascular Regulation Cardiovascular regulation changes blood flow to a specific area At an appropriate time In the right area Without changing blood pressure and blood flow to vital organs (Ex: ______________) Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiovascular Regulation Figure 21–13 Short-Term and Long-Term Cardiovascular Responses Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiovascular Regulation Controlling Cardiac Output and Blood Pressure Autoregulation Causes immediate, localized homeostatic adjustments Neural mechanisms Respond quickly to changes at specific sites Endocrine mechanisms Direct long-term changes Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiovascular Regulation Autoregulation of Blood Flow within Tissues- Adjusted by Peripheral Resistance while CO stays the same Can cause local vasoconstriction or vasodialation Triggered by prostaglandins and other “local” factors Local vasoconstrictors can reduce blood flow by: Constricting precapillary sphincters Affecting a single capillary bed Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiovascular Regulation Autoregulation of Blood Flow within Tissues- Local vasodilators can accelerate blood flow at tissue level if: low O2 or high CO2 levels low pH (acids) nitric oxide (NO) levels high high K+ or H+ concentrations chemicals released by inflammation (histamine) elevated local temperature Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiovascular Regulation Neural Mechanisms Cardiovascular (CV) centers of the Medulla Oblongata Cardiac centers: cardioacceleratory center: increases cardiac output cardioinhibitory center: reduces cardiac output Vasomotor center: vasoconstriction controlled by adrenergic nerves (NE) stimulates smooth muscle contraction in arteriole walls vasodilation: controlled by cholinergic nerves (ACh) relaxes smooth muscle Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiovascular Regulation Vasomotor Tone Maintained by constant action of sympathetic vasoconstrictor nerves Keeps your blood pressure high enough to get good capillary exchange! Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiovascular Regulation Reflex Control of Cardiovascular Function Cardiovascular centers monitor arterial blood Baroreceptor reflexes: respond to changes in blood pressure Chemoreceptor reflexes: respond to changes in chemical composition, particularly pH and dissolved gases Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiovascular Regulation Baroreceptor Reflexes Stretch receptors in walls of Carotid sinuses: maintain blood flow to brain Aortic sinuses: monitor start of systemic circuit Right atrium: monitors end of systemic circuit When blood pressure rises, CV centers Decrease cardiac output Cause peripheral vasodilation When blood pressure falls, CV centers Increase cardiac output Cause peripheral vasoconstriction Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiovascular Regulation Figure 21–14 Baroreceptor Reflexes of the Carotid and Aortic Sinuses Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiovascular Regulation CNS Activities and the Cardiovascular Centers Thought processes and emotional states can elevate blood pressure by cardiac stimulation and vasoconstriction Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiovascular Regulation Hormones and Cardiovascular Regulation Hormones have short-term and long-term effects on cardiovascular regulation E and NE from suprarenal medullae stimulate cardiac output and peripheral vasoconstriction Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiovascular Regulation Antidiuretic Hormone (ADH) Released by neurohypophysis (posterior lobe of pituitary) Elevates blood pressure Reduces water loss at kidneys ADH responds to: Low blood volume High plasma osmotic concentration Circulating angiotensin II Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiovascular Regulation Angiotensin II Responds to fall in renal blood pressure Stimulates Aldosterone production ADH production Thirst Cardiac output Peripheral vasoconstriction Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiovascular Regulation Erythropoietin (EPO) Released at kidneys Responds to low blood pressure, low O2 content in blood Stimulates red blood cell production Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiovascular Regulation Natriuretic Peptides Atrial natriuretic peptide (ANP) Produced by cells in right atrium Brain natriuretic peptide (BNP) Produced by ventricular muscle cells Respond to excessive diastolic stretching Will lower blood volume and blood pressure And reduce stress on heart Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiovascular Regulation Figure 21–16a The Hormonal Regulation of BP and BV Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiovascular Regulation Figure 21–16b The Hormonal Regulation of BP and BV Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiovascular Adaptation Blood, heart, and cardiovascular system Work together as unit Respond to physical and physiological changes (for example, exercise, blood loss) Maintains homeostasis Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiovascular Adaptation The Cardiovascular Response to Exercise Light exercise Extensive vasodilation occurs: increasing circulation Venous return increases: with muscle contractions Cardiac output rises: due to rise in venous return (Frank–Starling principle) and atrial stretching Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiovascular Adaptation The Cardiovascular Response to Exercise Heavy exercise Activates sympathetic nervous system Cardiac output increases to maximum: about 4 x resting level Restricts blood flow to “nonessential” organs (e.g., digestive system) Redirects blood flow to skeletal muscles, lungs, and heart, skin Blood supply to brain is unaffected Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiovascular Adaptation Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiovascular Adaptation Exercise, Cardiovascular Fitness, and Health Regular moderate exercise ______ total blood cholesterol levels Intense exercise Can cause severe physiological stress Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiovascular Adaptation Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiovascular Adaptation The Cardiovascular Response to Hemorrhaging Entire cardiovascular system adjusts to Maintain blood pressure Restore blood volume Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiovascular Adaptation Shock Short-term responses compensate after blood losses of up to 20% of total blood volume Failure to restore blood pressure results in shock Organ systems start to fail Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiovascular Adaptation Vascular Supply to Special Regions Blood Flow to the Brain is top priority due to high oxygen demand When peripheral vessels constrict, cerebral vessels dilate, normalizing blood flow to brain Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiovascular Adaptation Stroke Also called cerebrovascular accident (CVA) Blockage or rupture in a cerebral artery Maybe due to aneurism rupture Stops blood flow to brain Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiovascular Adaptation Blood Flow to the Heart Through coronary arteries Oxygen demand increases with activity Rising Lactic acid and low O2 levels Dilate coronary vessels Increase coronary blood flow Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiovascular Adaptation Heart Attack (Myocardial Infarction/MI) A blockage of coronary blood flow Can cause: Angina (chest pain) Tissue damage Heart failure Death Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Cardiovascular Adaptation Blood Flow to the Lungs Regulated by O2 levels in alveoli High O2 content in alveolus Vessels dilate, _______ cap exchange Low O2 content in alveolus Vessels constrict, _______cap exchange Shunts blood to other O2rich alveoli Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Aging and the Cardiovascular System Cardiovascular capabilities decline with increasing age Age-related changes occur in: Blood Heart Blood vessels Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Aging and the Cardiovascular System 3 Age-Related Changes in Blood Decreased hematocrit Peripheral blockage by blood clot (thrombus) Pooling of blood in legs Due to venous valve deterioration Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Aging and the Cardiovascular System 5 Age-Related Changes in the Heart Reduced maximum cardiac output Changes in nodal and conducting cells Reduced elasticity of cardiac (fibrous) skeleton Progressive atherosclerosis Replacement of damaged cardiac muscle cells by scar tissue Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Aging and the Cardiovascular System 3 Age-Related Changes in Blood Vessels Arteries become less elastic Pressure change can cause aneurysm Calcium deposits on vessel walls Can cause stroke or infarction Thrombi can form At atherosclerotic plaques Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings