QUANTITATIVE ENGR PHYSIOL I
QUANTITATIVE ENGR PHYSIOL I BME 365R
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This 50 page Class Notes was uploaded by Karianne Harber on Sunday September 6, 2015. The Class Notes belongs to BME 365R at University of Texas at Austin taught by Staff in Fall. Since its upload, it has received 40 views. For similar materials see /class/181694/bme-365r-university-of-texas-at-austin in Biomedical Engineering at University of Texas at Austin.
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Date Created: 09/06/15
BME 365 Quantitativ Physiology A Lecture 16 Cardiovascular System Outline Overview of CV System Functions Elements Factors Affecting Blood Flow Cardiac Muscle and the Heart The Heart Cardiac Muscle a Contraction a Action Potentials Heart as a Pump Coordinated Electrical Contraction EKG Factors Affecting Cardiac Output Outline Overview of CV System Functions Elements Factors Affecting Blood Flow Cardiac Muscle and the Heart The Heart Cardiac Muscle a Contraction a Action Potentials Heart as a Pump Coordinated Electrical Contraction EKG Factors Affecting Cardiac Output Overview of CV System Functions Cells need oxygen nutrients Oxygen can diffuse a limited distance Solution evolution of a circulatory system Elements Heart Blood vessels I BIOOCI Clamri Alumsquot mum u m quotMquot Hg M 1 7 camera anatumy uf the mrcmatury system S venhum 2m Ed Outline Overview of CV System Functions Elements Factors Affecting Blood Flow Cardiac Muscle and the Heart The Heart Cardiac Muscle a Contraction a Action Potentials Heart as a Pump Coordinated Electrical Contraction EKG Factors Affecting Cardiac Output Factors Affecting Blood Flow Flow rate FdAWR Resistance to flow R 8Ln7cr4 Velocity of flow I v Fcross sectional area I Terms F flow rate volume of blood passing point in system per unit time Lmin AP pressure gradient R resistance to flow vasoconstrictiondilation n fluid viscosity r vessel radius v velocity of flow The Heart a Four chambers encased in pericardium m Composed of Cardiac muscle myocardium Thin layer of epithelium and connective tissue a Valves ensure one way flow of blood AV valves separate atria and ventricles Semilunar valves separate ventricles and vessels 3 Coronary arteries Supply myocardium with blood Position of Stemum Esemllunar valves First ribcut quot heart Position of AV valves Apexaf Diaphragm hequot The heart is on the ventral side of the thoracic cavity sandwiched between the lungs Superior vlew of transverse plane In B segment removed Superlo p i ht Perlcardlal cavlly ventricle Pericardium lbssels that carry welloxygenated blood are red those with less welloxygenated blood are blue Fig 147 ad The Cardiovascular System Silverthorn 2nd Ed Aorta Pulmonary artery Left atrium Diaphragm The heart is encased within a membranous fluidfilled sac the pericardium ulman 39mnumrnm The venlricles occupy the bulk Le pulmonary olthe s andvelns all anarlu anachlo the based the heart lnlercalated disks Myocardial muscle cell Right pulmonary analIn cuepol left AV blempl valve Gnome lemmee Cuspuhighmv tricuuplrl alva Plpilllry muscles Myocardial musclaoells are branchedhave a single nucleusand are attachedto each otherby specialized iunctions known as intercala led disks ighlvsmrlcle Silverthorn 2quotd Ed Onewayllnwlhnughlhe hear ensured by two not valves Fig 147 eh The Cardiovascular system Transverse sectlon Tncupld Fllmus murame AV lighIAV vulva skeleton or hicuspid cloud Valvalclosgd orlic Aorlll samllunnr aamllunur valveopen valveopsn hrSH Papillary muscles Pulmonary tense nemllunar 39 valvenpen Ld vemricle contracted Mllrnlle AVnr Transverse section blcu3p lvalvg 0PM semllnnur quotmumquot valveclosed vulva closed Trlcuspld valve open Pnllnltlmary nun unar valve closed Lellvemrlcle dllaled Fig 149 Heart Valves Silverthorn 2Hd Ed Blood Pressure My blood pressure 10368 The higher systolic number represents the pressure while the heart is beating The lower diastolic number represents the pressure when the heart is resting between beats Normal blood pressure Varies from minute to minute Varies with changes in posture Should be lt 12080 mm Hg for an adult Prehypertension Blood pressure that stays between 1201398089 Hypertension Blood pressure above 14090 mm Hg How Do We Measure BP 3 Sphygmomanometer Increase cuff pressure until it is higher than systolic pressure Blood flow into arm stops Gradually release pressure When cuff pressure systolic pressure Blood begins to flow again Hear Korotkoff sound associated with turbulent flow through artery When cuff pressure diastolic pressure Artery is no longer compressed No longer hear Korotkoff sound How Do We Measure Blood Pressure Cardiac Muscle a Most cardiac muscle is contractile Striated muscle with contractile fibers organized into sarcomeres Smaller than muscle cells I Have single nucleus 13 of volume is mitochondria Cardiac muscle extracts 7080 of oxygen delivered by blood 2X amount extracted by other tissues 1 1 of myocardial cells are specialized Generate APs spontaneously Called autorhythmic cells or pacemakers Do not have sarcomeres Give heart ability to contract wo outside signal Inmalnbeddisk lac nnad Immulateddlsk Mllochandrla Nuclau Dermal muscle cell Conncillellban F g 14107Cardwac musde S venhom 2 Ed Cardiac Muscle a Intercalated disks Cardiac muscle cells branch and join neighboring cells end to end at these disks Interdigitating membranes tightly linked by desmosomes Allow force created in one cell to be transmitted to adjacent cell Also contain gap junctions Linked transmembrane proteins Allow direct movement of ions from one cell to net cell Electrically couple heart muscle so that waves of depolarization can contract almost simultaneously Contraction in Cardiac Muscle m Occurs via sliding filament movement as in skeletal muscle a An AP is required to initiate contraction AP opens voltage gated calcium channels Calcium enters cell Influx of calcium triggers release of calcium from SR 90 of calcium required for calcium Binds to troponin to start contraction Relaxation occurs when calcium unbinds from troponin Calcium transported back to SR with help of calcium ATPase wxumnm u wmmmu mm uymmm 0 Mr K mwmmm from Idlieenl aquot h wmm o mm ch mm lnu mm mm c mwll nln ullcll m Enuymmmaw o 0 o e a mums 5 9 0 o c ammmmm Mum m 2 mm 2 WWW QM o 0 0 9 mmquot mm WWW m o 2 Inn mm to Italianquot m luluu mmmn mm lmpunln mm F g 14117R0e ofcamum m Cardwac musde Contracuon SHverthom 2 Ed Graded Cardiac Muscle Contraction a Single cardiac muscle fiber can vary amount of force It generates Skeletal muscle is all or none 3 Force generated or active crossbridges Number of active crossbridges is determined by cytosolic calcium concentration Regulated by epinephrine and norepinephrine a For both cardiac and skeletal muscle Force of contraction depends of sarcomere length at beginning of contraction Depends on overlap between thin and thick filaments BUT in cardiac muscle stretching can also allow additional calcium to enter 9 more forceful contraction Tension of maximum 100 80 60 4O 20 Skeletal muscle ardiac muscle 60 70 80 90 Sarcomere length of maximum 100 APs in Cardiac Muscle r Myocardial contractile cells Similar to APs in neurons and skeletal muscle Rapid depol due to Na entry Steep repol due to K leaving Main difference Lengthening of AP due to calcium entry 3 Stable resting potential of 90 mV a Wave of depol comes in from neighboring cells via gap junctions Wu PX Penneabilhyloionx l PKamHFC Membrane pole Ina Time msec Phase Membrane channels Na channels open 9 Na39 channels close cab channels npenfas1 K39 channels clase ca channels close slow K channels open nestlng potential Flg 1414 r Actlon potentlal of a Cardlac Contractlle CeH Sllverthom 2 Ed APs in Cardiac Muscle a AP Opens voltage gated Na channels Na entry 9 rapid depol to 20 mV Doubly gated Na channels close K leaves through open K channels 9 cell begins repol AP flattens into plateau clue to Decreased K permeability as fast K channels close Increase in calcium permeability due to opening of voltage gated calcium channels Calcium channels close and slow K channels open K exits and cell repolarizes Influx of calcium lengthens AP 3 Muscle 15 ms 1 Cardiac cell 200 ms 9 prevents tetanus Skeletal muscle fasttwitch fiber Tat 1quot a SIKe39eta39 quot USC39B39 Action potentials not shown 5 Maximum g Refractory tension period 5 5 A Stimulus for action g g potential 0 C E g 2 E I E A A A A A A A A A o 75 150 Time msec A Time msec Stlmulus Long refractory period in a cardiac muscle prevents tetanus Cardiac muscle fiber A g gt E 5 E E quotE E 5 5 391 o C 0 5 9 o u E 5 o n l o g s E O O O 100 200 250 A Time msec Stimulus Time msec Fig 1415 Refractory period in skeletal and cardiac muscle Silverthorn 2er Ed Autorhythmic Cells a Unstable membrane potential Starts at 60 mV and slowly drifts up I When it reaches threshold AP is fired a Different ion channels I At mV Both K Na channels are open If channels Na influx gt K efflux Slowly depolarizes cell As membrane potential becomes more positive If channels close Calcium channels open many at threshold Influx of calcium depolarizes cell At peak of AP Calcium channels close Slow K channels open Repolarization occurs Pacemaker and action potentials Membrane potential mV 20 11me gt o 20 Threshol 60 4 Pacemaker Action potential potential Ion movements during an action We Various 3quot mama39s and pacemaker potential 40412quot channels 2 channels open Lots of Ca Ca in K out channels open c32 in Some Ca2 channels open ll channels close If channels Net Na in If channels 0P9quot open K channels close Fig 1416 Action potentials in cardiac autorythmic cells Silverthom 2 Ed Timing of Autorhythmic APs Sensitive to Altered ion channel permeability Norepinephrine and epinephrine Increase If and calcium channel permeability Increase rate of AP firing Outline Overview of CV System Functions Elements Factors Affecting Blood Flow Cardiac Muscle and the Heart The Heart Cardiac Muscle a Contraction a Action Potentials Heart as a Pump Coordinated Electrical Contraction EKG Factors Affecting Cardiac Output Heart as a Pump Coordinated electrical conduction The noncontractile autorhythmic cells form an anatomic pattern in the heart SA node Group of cells in top of right atrium Set pace of heart Internodal pathway Connects SA node to AV node AV node Group of cells near floor of right atrium Bundle of HIS Purkinje fibers 5A nodedepolnrlzes Electrical acuvlly goes rapidly lo AV nodevIu quot lmernndal pamw ys Depolarization wave spmads upward quotum lhe apex Fig 1419 Electrical conduction in the hean Silvelthorn 2 d Ed Heart as a Pump SA node initiates wave of atrial contraction Fibrous skeleton of heart at AV junction prevents transmission of APs except to AV node APs from AV node initiate ventricular contraction AV node delay Ventricular contraction always follows atrial contraction SA node Highest rate of spontaneous AP generation Sets heart rate EKG Recording of electrical activity of heart Made from electrodes placed on skin surface Signals weak buy the time they reach skin surface I 100 mV at heart I 1 mV at skin EKG shows sum of electrical potentials generated by all cells of heart at any time mph ques nn mm chm speed I 25 mm MC mmnne ham me at me Penaquot m 1 mm 1 um sq H914 21 rThe e ectrocardwogram Mllllvons o PH Imam ans unmplax m Interval SHvenhom 2 Ed EKG of One Cardiac Cycle P wave Atrial depolarization QRS complex Ventricular depolarization T wave Ventricular repolarization Hg 14 22 r Corre auon between depo a zauon and repo a zauon m the heart and m the ECG SHvenhom 2 Ed Cardiac Cycle 1 Heart at rest Atria filling with blood from veins Ventricles have just completed a contraction As ventricles relax AV valves open Blood flows from atria to ventricles 2 SA node fires Atria contract Push blood into ventricles Cardiac Cycle 3 AV node fires Ventricles begin to contract Forces AV valves closed 1St heart sound Semilunar valves still closed Isovolumic contraction Atria begin to repolarize and fill 4 Ventricles complete contraction Force SL valves open I Blood exits to arteries Cardiac Cycle 5 Ventricles relax SL valves close 2nd heart sound Lame dlaunle bollr sets n1 chamber relaxed Pnuiw vamriculnrlilling luvnlurnlc vemrlcular Alllal ayuole rallxallanl u valllllllcle relax f1mm mama n mm r a la Elam llaws back Into p 61 dlll blond Inln Id 0 aumllunar v vas and 39 venlrlcl s 5 V ED lI end alumna volume The maximum amount of blood In VennIsles occurs at me end a venlrlcular relaxatlon EDV 5155 mL r Esv end system volume nr mlnlmum amount 0 hlo ln venlrleles Esv a 55 mL Venlrlcular elecnun as venmcular pressure rlsee and exceeds pressure In the arteries he semllunar valves open and blood is elected lsovnllmllc vomrlcu ar continental quotrs has quot al vtnlrlculll con nictlull puslm AV valves cloud but due not mar annual plenum to open aamllunlr nlvar Flg 14 25 rThe Cardlac Cycle Sllvenhom 2 Ed Env End am I cvnluma esv Endsyle volume Stroke volume I20 A n m E mum Venll39lculnlelzc on gg gvnlw E closas a zsv 2 a M g c E lluvalumll s Ismmlumm 09mm 5 reluaxlon 5 111 gt E W MlirIvnlw claau EDV D gtA Isovolumlc relaxation Flg 14 26 7 Left venmcular pressurervolume changes durlng one cardlac cycle Sllvenhom 2quotd Ed m um H914 27 7mg Wager magram S venhum 2m Ed Quantifying Cardiac Performance Ventricles EDV end diastolic volume 135 ml ESV end systolic volume 65 ml Stroke volume SVEDVESV Amount of blood pumped by 1 ventricle in 1 contraction Cardiac output COHR x SV Amount of blood pumped per ventricle per unit time I 5Lmin Normal blood volume is N 5L Quantifying Heart Performance a Ejection Fraction EF Fraction of blood pumped out of ventricle relative to total volume at end diastole EF SVEDV Normal value gt 60 Measured using echocardiography a Normal echocardiogram httlowwwulltumcedukumcnedscardlolodvmovlesn llondecholabeledmm a Dilated cardiomyopathy nttpvawulltumcedulltumcpedscardioloclvmoviess ssmoviesdilcardlomvopsssnltth Factors Affecting CO Heart rate Parasympathetic activity decreases HR Sympathetic activity increases HR Stroke volume Depends on force generated by cardiac muscle during contraction Force is affected by a Lengthtension relation As sarcomere lengthens tension during contraction increases Starling s law b Contractility u Controlled by nervous and endocrine systems a Contractility increases as available calcium increases Y Normal mung values e 3 a ll smke v ume mL a 2m Son 400 stretch Indlcnmd by venh39icular enddlasiollc vaIume mL Hg 14 29 SHvenhum 2quotd Ed Stroke vnluma mL gt I Nnrepinephllne i l i i A Venl culnr enddllmllc volume mL H914 27 7mg Wager magram suvenhum 2nd Ed Outline Overview of CV System Functions Elements Factors Affecting Blood Flow Cardiac Muscle and the Heart The Heart Cardiac Muscle a Contraction a Action Potentials Heart as a Pump Coordinated Electrical Contraction EKG Factors Affecting Cardiac Output Poem of the Day Due Dates Tuesday November 2nd Homework 8
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