Chapter 21 cont'd. Chapter 22
Chapter 21 cont'd. Chapter 22 BIOL 224
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This 14 page Class Notes was uploaded by Gail Chernomorets on Sunday October 9, 2016. The Class Notes belongs to BIOL 224 at University of Nevada - Las Vegas taught by Sean Neiswenter in Fall 2016. Since its upload, it has received 24 views. For similar materials see Human Anatomy and Physiology II in Biology at University of Nevada - Las Vegas.
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Date Created: 10/09/16
10/04 & 10/06 Notes Chapter 21 cont’d. Capillary Bed (Capillary Plexus) Interconnected capillary bed allow blood to profuse through a tissue (not just a single tube) Arteriole to dozens of capillaries Precapillary sphincter - regulates flow into the capillary More than one artery = collaterals - feeds a tissue - come together at an arterial anastomosis Function - protection – if one artery becomes blocked, the other will continue to supply the capillary bed Arteriole junction - regulation of blood flow passes through Vasomotion The cycling of contraction and relaxation of capillary sphincters Blood flow in capillary beds constantly changes Controlled locally - environment immediately surrounding that sphincter - changes in the interstitial fluid - concentrated levels Veins Collect blood from capillaries Return to the heart Has all 3 tunicas just thinner Compared to arteries - larger in diameter - thinner walls - lower blood pressure Valves Not in arteries Folds of tunica intima Prevent backflow Compression from muscle Keep blood from going the wrong direction Blood Vessels The distribution of blood Heart, arteries, and capillaries contain 30-35% of blood volume Venous system contains 60-65% - 1/3 of venous blood is in the large venous networks of the liver, bone marrow, and skin Venous Response to Blood Loss Vasomotor center of the medulla oblongata stimulates sympathetic nerves innervating smooth muscle - response to blood loss is similar to response when you exercise 1. Systemic veins constrict (venoconstriction) Constriction of veins and pushes back to heart Reduces amount of blood in venous system which increases the volume within arterial system and capillaries 2. Veins in liver, skin, and lungs constrict and redistribute venous reserve (~20%) Blood flow to brain and other delicate organs can be maintained even after substantial blood loss Bleeding to death, response is increased HR, increased BP, and push blood faster out Pressure and Resistance Cardiovascular regulation maintains adequate blood flow through the capillaries - normally, blood flow equals cardiac output - **capillary blood flow is determined by pressure and resistance 2 processes - flow (F) pressure (P) resistance (R) - FαΔP F = ΔP - Fα 1/R proportional High resistance, low flow - pressure gradient is important - cardiac control centers change CO and R change pressure gradient change capillary blood flow Pressure 1. Blood pressure (BP) Arterial pressure in the systemic circuit 100mm Hg at aorta to 35mm Hg at capillary Mostly aorta or proxy of aorta 2. Capillary hydrostatic pressure (CHP) Force exerted by blood pressure against wall 35mm Hg to 18mm Hg along capillary Blood through capillary bed 3. Venous pressure 18mm Hg to 2mm Hg left atrium barely moving when you get to heart (2mm) leaves capillary venous system Circulatory Pressure The difference in pressure (ΔP) across the systemic circuit (about 100mm Hg) must overcome the total peripheral resistance in order for circulation to occur - need to exceed Resistance of the entire cardiovascular system reflects - combination of 3 things 1. Resistance Overall cardiac system within vessels 2. Viscosity Of blood 3. Turbulence Total Peripheral Resistance Useful in regulating blood flow Vascular resistance - opposes blood flow - friction = most important - depends on length and diameter length: 1:1, unit of length and unit of resistance diameter: 1:16, increase diameter, decrease resistance, increase diameter, move more blood than is in contact with vessels, resistance contact with vessel R increases at higher rate than vessel diameter decreases Viscosity Thickness tackiness Not super important in regulating blood flow but important in blood flow Water Honey Blood is in between Water has a low viscosity whereas honey has a high viscosity - whole blood is about five times more viscous than water Turbulence Swirling action disturbs flow Normal in heart chambers and great vessels Plaques cause abnormal turbulence Generally not normal except in heart chambers Move in one direction, stop, and go in other direction Overview of Cardiovascular Pressures Vessel diameters - aorta (large) to the capillaries vessels diverge and become smaller - capillaries to the vena cava vessels converge and become larger Total cross-sectional area - aorta (large) to the capillaries cross-sectional area increases - capillaries to the vena cava cross-sectional area decreases - blood pressure and velocity are affected by the cross-sectional area and diameter Pressure - aorta (large) to the capillaries resistance increases blood pressure falls venous pressures remain low despite R decrease Velocity of blood flow - aorta (large) to the capillaries blood velocity decreases - capillaries to the vena cava resistance decreases velocity increases Arterial Blood Pressure Systolic pressure - peak arterial pressure during ventricular systole Diastolic pressure - minimum arterial pressure during diastole Pulse pressure - difference between systolic pressure and diastolic pressure - PP = SP – DP ** arteries squirt blood ** veins drain blood **Mean arterial pressure (MAP) - MAP = diastolic pressure - + 1/3 pulse pressure ** be able to figure out on quiz - Normal BP 120/80 (max) Hypertension - is abnormally high BP - greater than 140/90 Hypotension - is abnormally low BP - less than 90/60 Elastic Rebound Arteries - stretch during systole and rebound during diastole - keeps blood moving during diastole Small arteries and arterioles MAP and pulse pressure decrease with distance Blood pressure decreases with resistance Pulse pressure decreases with elastic rebound Venous Pressure and Venous Return The amount of blood to right atrium per minute Venous pressure is low but sufficient because resistance is also low Venous flow is assisted by - muscular compression skeletal muscles and one way valves - respiratory pump inhale and exhale pressure in the thoracic cavity changes pumps inferior vena cava - gravity 1/3 or 1/5 above your heart Capillary Pressures and Capillary Exchange Diffusion, filtration, and reabsorption - most important to exchange Diffusion - movement of molecules from higher to lower concentration slow process 1. water, ions, and small molecules (glucose, AA) between endothelial cells through fenestrated capillaries + + 2+ - 2. many ions (Na , K , Ca , Cl ) through protein channels in endothelial cell plasma membranes allow ion to pass through cell instead of around Filtration Size selective movement Aid movement of fluid across endothelial wall with this process Movement of a fluid across a membrane whose pores restrict solutes based on size Cant fit through membrane - large things now allowed to pass Driven by hydrostatic pressure Capillary filtration - water and small solutes are forced across the capillary wall - larger solutes including proteins stay in blood Pressure of stable water - pressurizing it Force - actively - water, small solute through membrane Reabsorption Opposite – return of fluids to other side of membrane. Into the bloodstream The result of osmotic pressure (OP) - the force of osmotic water movement - dependent on - amount of solutes dissolved on one side compared to the other side Blood colloid osmotic pressure (BCOP) - caused by suspended blood proteins that are too large to cross capillary walls Possible test question: Difference between plasma and interstitial fluids? - plasma Interplay between filtration and reabsorption movement of fluids out of capillaries, through tissues, and back into the bloodstream (via lymphatic system) 1. Ensures that plasma and interstitial fluid are in constant communication and mutual exchange 2. Accelerates distribution of nutrients, hormones, and dissolved gases throughout tissues 3. Assists in the transport of insoluble lipids and tissue proteins that cannot enter bloodstream by crossing capillary walls 4. Has a flushing action that carries bacterial toxins and other chemical stimuli to lymphatic tissues and organs responsible for providing immunity to disease Purpose: Ensure even dispersion of blood and fluids and bad debris gets flushed to lymphatic system Net capillary hydrostatic pressure - tends to push water and solutes out of capillaries and into the interstitial fluid Net capillary colloid osmotic pressure - plasma proteins - tends to pull water and solutes into a capillary from the interstitial fluid Net filtration pressure - (NFP) - the difference between net hydrostatic pressure and net osmotic pressure - NFP = hydrostatic pressure – osmotic pressure - Overall difference between both - Movement continuous, pressure drops (+) value filtering (-) value absorbing Don’t recover all fluid, we filter (~10%) *Capillary Exchange Arterial end of a capillary, fluid moves out of blood NFP is positive = filtration Venous end of capillary, fluid moves into capillary NFP is negative = reabsorption Transition point is closer to venous end Capillaries filter more than they reabsorb - Excess fluid enters lymphatic vessels Any condition affecting hydrostatic or osmotic pressures alters capillary dynamics Hemorrhage, change in BP or blood volume, dehydration - losing blood volume Mechanism allows alteration Homeostatic Regulation Ensures tissue perfusion - movement of blood through tissue Meets demands for oxygen and nutrients Tissue perfusion is affected by - cardiac output - peripheral resistance (can be altered locally) - blood pressure - regulatory centers in medulla oblongata Cardiovascular regulation directs changes in blood flow - at the right time - in the right place - without changing pressure and flow to vital organs Blood flow to brain always the same never changes, if it does, you die Controlling Cardiac Output and Blood Pressure Autoregulation - causes immediate, localized homeostatic adjustments Neural mechanisms - respond quickly to changes at specific sites - neural stimulation - locally; ex. damage to tissue - very quickly Endocrine mechanisms - direct long-term changes Alter blood flow Autoregulation of Blood Flow within Tissues Under normal resting conditions, peripheral resistance is adjusted and cardiac output remains constant Local vasodilators – relaxation of the smooth muscle - precapillary sphincters - Low oxygen, high CO , l2w pH (acids), nitric oxide, high K or H , + inflammatory signals (histamine) leads to inflammation, elevated temperature Local vasoconstrictors – smooth muscle contraction - also release when vessels are damaged Neural Mechanisms Cardiovascular (CV) centers of the medulla oblongata Cardiac centers – regulate CO - cardioacceleratory (norepinephrine) and cardioinhibitory (Ach) Vasomotor centers - vasoconstriction (NE) increase BP very quickly - vasodilation (Ach/NO) decrease BP very quickly Vasoconstrictor nerves – vasomotor tone - 80 fold difference in resistance is possible Reflex Control of Cardiovascular Function Cardiovascular centers monitor arterial blood Baroreceptor reflexes respond to changes in pressure Chemoreceptor reflexes respond to changes in chemical composition, particularly pH and dissolved gases 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) Same monitors as heart can be used When blood pressure rises, CV centers: 1. Decrease cardiac output 2. Cause peripheral vasodilation When blood pressure falls, CV centers: 1. Increase cardiac output 2. Cause peripheral vasoconstriction Very fast, short lived response Chemoreceptor Reflexes Peripheral chemoreceptors in carotid bodies and aortic bodies - monitor blood Additional receptors monitor CSF - control respiratory function - control blood flow to brain - implies there is a large amount of waste in body that you aren’t getting rid of Hormones and Cardiovascular Regulation Hormones have short-term and long-term effects on cardiovascular regulation Can affect vasodilation For example, E and NE from adrenal medullae quickly stimulate cardiac output and peripheral vasoconstriction Antidiuretic Hormones (ADH) - affect BP - released by posterior pituitary in response to decreased blood volume - elevates blood pressure and volume via reduced water loss at kidneys and peripheral vasoconstriction - retains water - dehydration decrease BV Angiotension II - big mechanism - activated in response to fall in renal blood pressure – filter blood through BP - Secretion of + Aldosterone production Na retention in kidneys ADH production water reabsorption in kidneys - Thirst increased fluid intake - Increases cardiac output and peripheral vasoconstriction Erythropoietin (EPO) - moderate response long lasting affect compared to epinephrine - kidneys in response to low blood pressure or low oxygen - stimulates RBC production and vasoconstriction - end response to fix problem Natriuretic Peptides Reduce BP Released by RA as secondary function Cardiac muscle cells produce in response to stretching during diastole Increase sodium excretion at the kidneys Increased urine production Reduce thirst Block ADH, aldosterone, E, NE Stimulate peripheral vasodilation Sodium in urine caused by strain of amino acids Too much BP secretes and does opposite of aldosterone The Cardiovascular Response to Exercise Light exercise - extensive vasodilation, increased venous return drives increased cardiac output as a response - sympathetic stimulation from sinoatrial node Heavy exercise - cardiac output increases to maximum, restricted blood flow to “nonessential” organs to ensure adequate flow to skeletal muscles, lungs, and heart - blood flow excessive and goes to organs to disperse the large increase of blood - blood supply to brain is unaffected - cerebral spinal fluid doesn’t have buffers so when CO incre2se, pH changes - Shut certain systems down for a while so they aren’t entirely active Exercise, Cardiovascular Fitness, and Health Performance significantly improves with training Regular moderate exercise (30 min, 3-4 days) - lowers total blood cholesterol levels, cuts incidence of heart attack in half - only ~8% of adults exercise at recommended levels Intense exercise (iron-man) - Can cause severe physiological stress (heart attack, kidney failure) - Pushing to absolute limit can cause severe damage The Cardiovascular Response to Hemorrhaging Maintain blood pressure and restore blood volume Short-term elevation of blood pressure - counterintuitive increase BP and move more blood - 20% volume compensation - Carotid and aortic reflexes Peripheral vasoconstriction increased Heart rate Constrict BV and increase BP - sympathetic activation fight or flight mobilizes venous reserves (venoconstriction) arteriole vasoconstriction - Hormonal effects (NE&E) – what does it do? Hormonal fight or flight response Long term response of NE and E Long-term restoration of blood volume - recall of fluids from interstitial spaces into bloodstream - Aldosterone and ADH promote fluid retention and reabsorption - Thirst increases - Erythropoietin stimulates RBC production - Not seen on chart: BP decreases at capillary net reabsorption, pull fluid back in and increase blood volume Vascular Supply to Special Regions The brain – steady blood flow always - <2% of the total body weight - 12% of cardiac output (~750 ml/min) always The heart – more blood as activity increases Blood flow in lungs – regulated differently than the rest - High oxygen = dilation To get large concentration gradient Increase blood flow Low CO hi2h O va2odilation - Low oxygen = constriction Vasoconstriction Three General Functional Patterns 1. Peripheral artery and vein distribution is the same on the right and left more/less mirror image; symmetrical except near the heart 2. Same vessel different name in different locations 3. Tissues and organs usually have multiple arteries and veins Anastomoses Usually have a backup Effects of Aging and the Cardiovascular System Age-related changes in blood - Decreased hematocrit (# of RBC), peripheral blockage by blood clot (thrombus) (narrowing of arteries, more often occurs), pooling of blood on legs due to valve deterioration (become weaker) - Less O 2apacity Age-related changes in the heart - reduced maximum cardiac output, changes in conducting cells, reduced elasticity in cardiac skeleton, reduced cardiac circulation (atherosclerosis), accumulation of scar tissue - HR decreases in blood movement Age-related changes in blood vessels - reduced elasticity in vessel walls, accumulation of deposits, blood clot formation around plaques - blood flow movement decreases - causes it to stick and cause clots - more common when older An Introduction to the Lymphatic System and Immunity The lymphatic system includes the cells, tissues, and organs responsible for defending the body - big role - takes fluid from blood and cleans it from tissue and passes through ducts and lymph nodes act as filter - WBC actively cleaning and recognizing (ID) bacteria and pathogens to identify, mount response and remove from the body Environmental hazards - sharps/abrasive, chemicals, extreme temp., UV Pathogens - microscopic organisms that cause disease include viruses, bacteria, fungi, parasites - Each attacks in a specific way - Internal threats like cancer cells Doesn’t recognize that it doesn’t belong Recognize as own and have mechanisms to help with that - have to be able to resist/ defend against these attacks - generally easy to identify what doesn’t belong Immunity = ability to resist infection and disease - two forms, work together and independently - castle analogy 1. Innate (nonspecific) immunity Anatomical barriers General defenses ex. skin General defense Born with it Work against everything the same, no change 2. Adaptive (specific) immunity Alternative to innate Lymphocytes involved Specific pathogens aka immune response Identify pathogens by antigens looking for familiar surfaces on cells T-lymph: actively attack - holes are ways for foreign cells to get in past the skin prevention in them: mechanisms put in place to protect openings “Immune System” All cells and tissues involved in immunity - lymphatic system - components of integumentary, cardiovascular, respiratory, and digestive system Functions of the Lymphatic System Immunity - develop, store, release lymphocytes (WBC use lymph) - filters blood plasma/ interstitial fluid - detect and respond to pathogens Maintain osmotic balance - return capillary filtrate to blood T cells develop in thymus Transport - lipids from digestive system to blood - lacteals small lymphatics “milky white substance” 2% fat The Lymphatic System consists of 1. Lymph Larger amount of fat (minimal) A fluid similar to plasma without proteins Interstitial fluid enters the system 2. Lymphatic vessels (lymphatics) Return filtered fluid to circulation 3. Lymphoid tissues and lymphoid organs Scattered throughout systems 4. Lymphocytes Phagocytes, and other immune system cells WBCs Lymphatic Vessels Not a circuit formal; has a beginning and end Carry lymph Begin with lymphatic capillaries (terminal lymphatics) Similar anatomy to sinusoids - endothelial cells overlap - function as one-way valves - movement of fluid down through the system - cant fit large things (ex. whole cells) Fluids, solutes, pathogens, and cell debris enter but cant return to intercellular space Lymphatic Capillaries differ from blood capillaries 1. Start as pockets rather than tubes 2. Have larger diameters 3. Have thinner walls 4. Flat or irregular outline Low pressure - cross-section irregular in shape Major Lymph-Collecting Vessels 2 major routes to collecting lymph and take to heart right lymphatic duct 1/4 - empties into the right subclavian vein - drains the right side of the body superior to the diaphragm thoracic duct 3/4 - empties into left subclavian vein - large - drains rest of the body Lymphocytes 20-30% of circulating leukocytes 1 trillion in body - combined = more than a kilogram (weight) Most lymphocytes are stored, not circulating Types of Lymphocytes Mature in thymus Originate in bone marrow, leave and enter thymus 1. T cells = thymus- dependent 2. B cells = bone-marrow derives 3. NK cells – natural killer cells Adaptive Immune System T cells Cytotoxic T cells - attack foreign cells or body cells infected by viruses - actively search for cells with antigens they recognize - secrete chemicals and destroy cells Helper T cells - stimulate and activation and function of both T cells and B cells - help adaptive immune system - assist in functions Suppressor T cells - inhibit the activation and function of both T cells and B cells - divide and make more of itself to search for more antigens and these go in and suppress immune response - **Remember antigens
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