Heart physiololgy.pptx

First stage Physiology course UOWA. Nursing college Cardiac physiology ‫د نسيم سمير علي صقر‬. ‫م‬.‫أ‬ 2024 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Heart Anatomy Figure 18.1 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Coverings of the He...

First stage Physiology course UOWA. Nursing college Cardiac physiology ‫د نسيم سمير علي صقر‬. ‫م‬.‫أ‬ 2024 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Heart Anatomy Figure 18.1 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Coverings of the Heart: Physiology  The pericardium:  Protects and anchors the heart  Prevents overfilling of the heart with blood  Allows for the heart to work in a relatively frictionfree environment 3 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Pericardial Layers of the Heart Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings External Heart: Anterior View 5 18.4b Figure Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Gross Anatomy of Heart: Frontal Section 6 18.4e Figure Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Pathway of Blood Through the Heart and Lungs  Right atrium  tricuspid valve  right ventricle  Right ventricle  pulmonary semilunar valve  pulmonary arteries  lungs  Lungs  pulmonary veins  left atrium  Left atrium  bicuspid valve  left ventricle  Left ventricle  aortic semilunar valve  aorta  Aorta  systemic circulation 7 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Pathway of Blood Through the Heart and Lungs 8 18.5 Figure Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Coronary Circulation  Coronary circulation is the functional blood supply to the heart muscle itself  Collateral routes ensure blood delivery to heart even if major vessels are occluded 9 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Heart Valves  Heart valves ensure unidirectional blood flow through the heart  Atrioventricular (AV) valves lie between the atria and the ventricles  AV valves prevent backflow into the atria when ventricles contract  Chordae tendineae anchor AV valves to papillary muscles 10 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Heart Valves  Aortic semilunar valve lies between the left ventricle and the aorta  Pulmonary semilunar valve lies between the right ventricle and pulmonary trunk  Semilunar valves prevent backflow of blood into the ventricles 11 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Heart Valves 1218.8a, b Figure Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Heart Valves 1318.8c, d Figure Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Atrioventricular Valve Function 14 18.9 Figure Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Semilunar Valve Function 15 18.10 Figure Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Anatomy of Heart Muscle  Cardiac muscle is striated, short, fat, branched, and interconnected  The connective tissue endomysium acts as both tendon and insertion  Intercalated discs anchor cardiac cells together and allow free passage of ions  Heart muscle behaves as a functional syncytium PLAY InterActive Physiology®: Cardiovascular System: Anatomy Review: The Heart 16 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Anatomy of Heart Muscle 17 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 18.11 Cardiac Muscle Contraction  Heart muscle:  Is stimulated by nerves and is self-excitable (automaticity)  Contracts as a unit  Has a long (250 ms) absolute refractory period  Cardiac muscle contraction is similar to skeletal muscle contraction 18 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Heart Physiology: Intrinsic Conduction System  Autorhythmic cells:  Initiate action potentials  Have unstable resting potentials called pacemaker potentials  Use calcium influx (rather than sodium) for rising phase of the action potential 19 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings 20 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings 21 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings 22 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Heart Physiology: Sequence of Excitation  Sinoatrial (SA) node generates impulses about 75 times/minute  Atrioventricular (AV) node delays the impulse approximately 0.1 second  Impulse passes from atria to ventricles via the atrioventricular bundle (bundle of His) 23 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Heart Physiology: Sequence of Excitation  AV bundle splits into two pathways in the interventricular septum (bundle branches)  Bundle branches carry the impulse toward the apex of the heart  Purkinje fibers carry the impulse to the heart apex and ventricular walls 24 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Heart Physiology: Sequence of Excitation 25 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 18.14a Heart Excitation Related to ECG 26 18.17 Figure Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Extrinsic Innervation of the Heart  Heart is stimulated by the sympathetic cardioacceleratory center  Heart is inhibited by the parasympathetic cardioinhibitory center 27 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 18.15 Electrocardiography  Electrical activity is recorded by electrocardiogram (ECG)  P wave corresponds to depolarization of SA node  QRS complex corresponds to ventricular depolarization  T wave corresponds to ventricular repolarization  Atrial repolarization record is masked by the larger QRS complex PLAY InterActive Physiology®: Cardiovascular System: Intrinsic Conduction System Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings 28 Electrocardiography 29 18.16 Figure Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Heart Sounds  Heart sounds (lub-dup) are associated with closing of heart valves  First sound occurs as AV valves close and signifies beginning of systole  Second sound occurs when SL valves close at the beginning of ventricular diastole 30 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Cardiac Cycle  Cardiac cycle refers to all events associated with blood flow through the heart  Systole – contraction of heart muscle  Diastole – relaxation of heart muscle 31 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Phases of the Cardiac Cycle  Ventricular filling – mid-to-late diastole  Heart blood pressure is low as blood enters atria and flows into ventricles  AV valves are open, then atrial systole occurs 32 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Phases of the Cardiac Cycle  Ventricular systole  Atria relax  Rising ventricular pressure results in closing of AV valves  Isovolumetric contraction phase  Ventricular ejection phase opens semilunar valves 33 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Phases of the Cardiac Cycle  Isovolumetric relaxation – early diastole  Ventricles relax  Backflow of blood in aorta and pulmonary trunk closes semilunar valves  Dicrotic notch – brief rise in aortic pressure caused by backflow of blood rebounding off semilunar valves PLAY InterActive Physiology®: Cardiovascular System: Cardiac Cycle 34 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Phases of the Cardiac Cycle 35 18.20 Figure Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Cardiac Output (CO) and Reserve  CO is the amount of blood pumped by each ventricle in one minute  CO is the product of heart rate (HR) and stroke volume (SV)  HR is the number of heart beats per minute  SV is the amount of blood pumped out by a ventricle with each beat  Cardiac reserve is the difference between resting and maximal CO 36 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Cardiac Output: Example  CO (ml/min) = HR (75 beats/min) x SV (70 ml/beat)  CO = 5250 ml/min (5.25 L/min) 37 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Regulation of Stroke Volume  SV = end diastolic volume (EDV) minus end systolic volume (ESV)  EDV = amount of blood collected in a ventricle during diastole  ESV = amount of blood remaining in a ventricle after contraction 38 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Factors Affecting Stroke Volume  Preload – amount ventricles are stretched by contained blood  Contractility – cardiac cell contractile force due to factors other than EDV  Afterload – back pressure exerted by blood in the large arteries leaving the heart 39 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Frank-Starling Law of the Heart  Preload, or degree of stretch, of cardiac muscle cells before they contract is the critical factor controlling stroke volume  Slow heartbeat and exercise increase venous return to the heart, increasing SV  Blood loss and extremely rapid heartbeat decrease SV 40 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Preload and Afterload 41 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 18.21 Extrinsic Factors Influencing Stroke Volume  Contractility is the increase in contractile strength, independent of stretch and EDV  Increase in contractility comes from:  Increased sympathetic stimuli  Certain hormones  Ca2+ and some drugs 42 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Extrinsic Factors Influencing Stroke Volume  Agents/factors that decrease contractility include:  Acidosis  Increased extracellular K+  Calcium channel blockers 43 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Contractility and Norepinephrine  Sympathetic stimulation releases norepinephrine and initiates a cyclic AMP secondmessenger system 44 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 18.22 Regulation of Heart Rate: Autonomic Nervous System  Sympathetic nervous system (SNS) stimulation is activated by stress, anxiety, excitement, or exercise  Parasympathetic nervous system (PNS) stimulation is mediated by acetylcholine and opposes the SNS  PNS dominates the autonomic stimulation, slowing heart rate and causing vagal tone 45 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Atrial (Bainbridge) Reflex  Atrial (Bainbridge) reflex – a sympathetic reflex initiated by increased blood in the atria  Causes stimulation of the SA node  Stimulates baroreceptors in the atria, causing increased SNS stimulation 46 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Chemical Regulation of the Heart  The hormones epinephrine and thyroxine increase heart rate  Intra- and extracellular ion concentrations must be maintained for normal heart function PLAY InterActive Physiology®: Cardiovascular System: Cardiac Output 47 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Factors Involved in Regulation of Cardiac Output 48 18.23 Figure Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Examples of Congenital Heart Defects 49 18.25 Figure Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings