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Functions of the Heart • Generaqon of Blood Pressure • Rouqng of Blood

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Functions of the Heart • Generaqon of Blood Pressure • Rouqng of Blood Functions of the Heart • Generaon of blood pressure • Rou'ng of blood • Ensuring unidirecon flow of blood • Regula'on of blood supply 1 2 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduc'on or display. CO2 O2 Pulmonary circuit O2-poor, CO2-rich O2-rich, blood CO2-poor blood Systemic circuit CO2 O2 3 4 5 6 7 8 9 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduc'on or display. Le AV (bicuspid) valve Right AV (tricuspid) valve Fibrous skeleton Openings to coronary arteries AorCc valve Pulmonary valve (a) 10 11 12 13 14 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduc'on or display. 10 1 Blood enters right atrium from superior and inferior venae cavae. 2 Blood in right atrium flows through right Aorta Le pulmonary AV valve into right ventricle. 11 artery 3 Contracon of right ventricle forces 5 5 pulmonary valve open. 4 Blood flows through pulmonary valve 9 Pulmonary trunk Superior into pulmonary trunk. vena cava 4 Le pulmonary 6 5 Blood is distributed by right and le veins pulmonary arteries to the lungs, where it Right 6 unloads CO and loads O . pulmonary 2 2 Le atrium veins 1 AorCc valve 6 Blood returns from lungs via pulmonary veins to leE atrium. 3 7 Le AV 7 Blood in le atrium flows through le AV Right (bicuspid) valve 8 valve into leE ventricle. atrium Le ventricle 2 8 Contracon of leE ventricle (simultaneous with Right AV step 3 ) forces aorCc valve open. (tricuspid) valve 9 Blood flows through aorCc valve into Right ascending aorta. ventricle 10 Blood in aorta is distributed to every organ in Inferior 11 vena cava the body, where it unloads O2 and loads CO2. 11 Blood returns to heart via venae cavae. 15 16 17 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduc'on or display. StriaCons Nucleus Intercalated discs (a) Striated myofibril Glycogen Nucleus Mitochondria Intercalated discs (b) Intercellular space Desmosomes Gap juncons (c) a: © Ed Reschke 18 19 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduc'on or display. 1 SA node fires. 2 ExcitaCon spreads through Right atrium 1 2 atrial myocardium. Sinoatrial node (pacemaker) Le 3 AV node fires. atrium 2 Purkinje 3 ExcitaCon spreads down AV Atrioventricular fibers 4 node bundle. Bundle Atrioventricular branches 5 Purkinje fibers distribute bundle 4 5 excitaCon through ventricular myocardium. Purkinje fibers 20 21 22 23 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduc'on or display. R R +1 PQ ST segment segment P wave T wave Millivolts 0 PR Q interval S QT interval QRS interval –1 Atria Ventricles Atria Ventricles contract contract contract contract 24 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduc'on or display. Key Wave of depolarizaCon R Wave of repolarizaCon P P Q S 1 Atria begin depolarizing. 4 Ventricular depolarizaCon complete. R P P T Q S 2 Atrial depolarizaCon complete. 5 Ventricular repolarizaCon begins at apex and progresses superiorly. R R P P T Q Q S 3 Ventricular depolarizaCon begins at apex and 6 Ventricular repolarizaCon complete; heart is progresses superiorly as atria repolarize. ready for the next cycle. 25 26 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduc'on or display. Diastole Systole Diastole 120 AorCc pressure 100 80 AorCc valve AorCc valve Le closes opens 60 ventricular (dicroc notch) pressure AV 40 valve AV Pressure (mm Hg) Le atrial valve closes 20 pressure opens 0 120 End-diastolic volume 90 Ventricular volume (mL) 60 End-systolic volume R R T P P ECG Q Q S S Heart sounds S2 S3 S1 S2 S3 S1 Phase of 1a 1b 1c 2 3 4 1a 1b 1c 2 cardiac cycle 0 .2 .4 .6 .8 .2 .4 Time (sec) Ventricular filling 2 3 4 1a Rapid filling 1c Atrial systole Isovolumetric Ventricular Isovolumetric 1b Diastasis contracCon ejecon relaxaCon 27 28 29 MAP ∝ CO × PR CO = HR × SV € MAP is mean arterial pressure CO is cardiac output € PR is peripheral resistance HR is heart rate SV is stroke Volume 30 31 32 33 34 .
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