SECTON IV CIRCULATION Chapter 9~11

Introduction Definition of circulation Function of circulation Circulatory system is made up of the heart and vessels in which blood is flowing in certain direction, going round and begin again Function of circulation Cardiovascular system transport the blood flow circulating the whole body, maintain the homeostasis Heart---- as a blood pump Vessels---- distributing and collecting the blood flow SECTON VI CIRCULATION Chapter 9~11 2009-09

Introduction Pulmonary circulation Gases exchange in the lungs Systemic circulations Metabolic substances exchange in every well of the body SECTON VI CIRCULATION Chapter 9~11 2009-09

Introduction Non-circulation function The heart and vessels as the endocrine organs Atrial natriuretic peptide (ANP)… Endothelin (ET)… SECTON VI CIRCULATION Chapter 9~11 2009-09

Content of the course CHAP 9 ELECTRICAL PROPERTIES OF THE CARDIAC MUSCLE CHAP 10 THE ELECTROCARDIOGRAM CHAP 11 THE HEART AS A PUMP CHAP 12 DYNAMICS OF BLOOD AND LYMPH FLOW CHAP 13 CARDIOVASCULAR REGULATORY MECHANISMS CHAP 14 CIRCULATION THROUGH SPECIAL REGIONS SECTON VI CIRCULATION Chapter 9~11 2009-09

CHAP 9 ELECTRICAL PROPERTIES OF THE CARDIAC MUSCLE 9.1 INTRODUCTION 9.2 RESTING MEMBRANE POTENTIAL AND ACTION POTENTIAL 9.3 ORIGIN AND SPREAD OF CARDIAC EXCITATION 9.4 EFFECT OF CARDIAC INNERVATION STIMULATION SECTON VI CIRCULATION Chapter 9~11 2009-09

9.1 INTRODUCTION Physiologic properties Conducting system Electrophysiological properties Excitability Autorhythmicity Conductivity Mechanical property Contractility Conducting system SECTON VI CIRCULATION Chapter 9~11 2009-09

9.1 INTRODUCTION Cardiac myocyte Electrical activity of myocardium Contractile myocardium Atrial muscles, ventricular muscles Autorhythmic myocardium S-A node, A-V node, bundle of His and its branches, Purkinje fibers Electrical activity of myocardium SECTON VI CIRCULATION Chapter 9~11 2009-09

9.2 RESTING MEMBRANE POTENTIAL AND ACTION POTENTIAL EK＝61.5·log [K+]o/ [K+]i ＝61.5·log [4]o/ [135]I ＝－90mv SECTON VI CIRCULATION Chapter 9~11 2009-09

9.2 RESTING MEMBRANE POTENTIAL AND ACTION POTENTIAL 9.2.2 The ion currents responsible for the action potential Ventricular action potential Depolarizing phase Phase 0 : INa, IK , ICa(L) Repolarizing phase Phase 1 : Ito Phase 2 : ICa (L) , IK Phase 3 : IK Phase 4 :resting state, active ion exchange SECTON VI CIRCULATION Chapter 9~11 2009-09

9.2 RESTING MEMBRANE POTENTIAL AND ACTION POTENTIAL Factors affecting excitability of myocardium Relationship of resting potential and threshold level Characters of Na+ channel Resting: Active: Inactive: effective refractory period SECTON VI CIRCULATION Chapter 9~11 2009-09

9.2 RESTING MEMBRANE POTENTIAL AND ACTION POTENTIAL 9.2.3 The pacemaker potentials S-A node action potential Auto-depolarizing phase—4: IK, ICa(T), INa(F), Ca2+ sparks Depolarizing phase—0: ICa(L) Repolarizing phase—3: IK Purkinje fibers 4: INa(F), IK SECTON VI CIRCULATION Chapter 9~11 2009-09

9.2 RESTING MEMBRANE POTENTIAL AND ACTION POTENTIAL Factors affecting autorhythmicity of myocardium Maximum diastolic potential Spontaneous depolarization Threshold potential SECTON VI CIRCULATION Chapter 9~11 2009-09

9.3 ORIGIN AND SPREAD OF CARDIAC EXCITATION 9.3.1 Anatomic consideration Spetial conductive system in heart SA node: normal pacemaker Autonomic innervations Right vagus and sympathetic nerve→ SA node Left vagus and sympathetic nerve→ A-V node SECTON VI CIRCULATION Chapter 9~11 2009-09

9.3 ORIGIN AND SPREAD OF CARDIAC EXCITATION Sequence of cardiac excitation Normal pacemaker: S-A node function as the pacemaker for the entire heart Latent or sub ordinary pacemaker Ectopic pacemaker Factors affecting conductivity Speed and amplitude of depolarization Excitability of neighbor cell SECTON VI CIRCULATION Chapter 9~11 2009-09

9.4 EFFECT OF CARDIAC INNERVATIONS STIMULATION 9.4.1 Effect of vagal cardiac nerves stimulation The parasympathetic postganglionic fibers release primarily acetylcholine (ACh), which binds to M2-receptors →G(γ) Inhibiting the heart actions 9.4.2 Effect of sympathetic cardiac nerves stimulation The sympathetic postganglionic fibers release primarily norepinephrine (NE), which binds mainly to 2-receptors →Gs Exciting the heart actions SECTON VI CIRCULATION Chapter 9~11 2009-09

CHAP 10 THE ELECTROCARDIOGRAM 10.1 RECORDING LEADS OF ECG 10.2 NORMAL ECG (EKG) SECTON VI CIRCULATION Chapter 9~11 2009-09

10.1 RECORDING LEADS OF ECG Basic principle Body is a volume conductor The heart is a current source in the center of a volume conductor (Einthoven's triangle) The ECG may be recorded by using an exploring electrod Depolarization moving toward an active electrode in a volume conductor produces a positive deflection, whereas depolarization moving in the opposite direction produces a negative deflection SECTON VI CIRCULATION Chapter 9~11 2009-09

10.1 RECORDING LEADS OF ECG Recording lead Waves of the ECG Bipolar recording Standard limb leads leads I, II, and III Augmented limb leads aVL, aVR, aVF Unipolar recording Precordial leads Waves of the ECG P, Q R S, T (,U) SECTON VI CIRCULATION Chapter 9~11 2009-09

10.2 NORMAL ECG (EKG) Duration of the ECG PR interval: 0.18s Atrial depolarization and conduction through AV node QRS duration: 0.08s Ventricular depolarization and atrial repolarization QT interval: 0.40s Ventricular depolarization plus ventricular repolarization ST interval: 0.32s Ventricular repolarization ST segment SECTON VI CIRCULATION Chapter 9~11 2009-09

CHAP 11 THE HEART AS A PUMP CHAP 11 THE HEART AS A PUMP 11.1 MECHANICAL PROPERTIES OF THE CARDIAC MUSCLE 11.2 MECHANICAL EVENTS OF THE CARDIAC CYCLE 11.3 CARDIAC OUTPUT 11.4 CARDIAC RESERVE SECTON VI CIRCULATION Chapter 9~11 2009-09

11.1 MECHANICAL PROPERTIES OF THE CARDIAC MUSCLE 11.1.1 Contractile response Dependent upon [Ca2+]o [Ca2+]i↑ triggered by Ca2+o No tetanus Contractile response lasts about 1.5 times as long as the action potential Long ERP: phase 0 →3(repolarization -50mv) Contraction in synchronism SECTON VI CIRCULATION Chapter 9~11 2009-09

11.1 MECHANICAL PROPERTIES OF THE CARDIAC MUSCLE 11.1.2 Relation between muscle fiber length and tension Starling‘s law of the heart (Frank-Starling law ) Energy of contraction is proportional to the initial length of the cardiac muscle fiber. The length of the muscle fibers (ie, the extent of the preload) is proportionate to the end-diastolic volume Heterometric regulation: dependent on initial length of myocardium fibers SECTON VI CIRCULATION Chapter 9~11 2009-09

11.1 MECHANICAL PROPERTIES OF THE CARDIAC MUSCLE Contractility— inotropic effect Homometric regulation: independent of initial length Active regulation by the organism SECTON VI CIRCULATION Chapter 9~11 2009-09

11.2 MECHANICAL EVENTS OF THE CARDIAC CYCLE Pumping function is periodicity action Heart rate: 60~100 beats/min Cardiac cycle: 0.8s (~72 beats/min) Systole and diastole Atria systole and diastole Ventricular systole and diastole Whole cardiac diastole SECTON VI CIRCULATION Chapter 9~11 2009-09

11.2 MECHANICAL EVENTS OF THE CARDIAC CYCLE Mechanism events: filling and ejection: driving the blood flow from vein to artery in certain direction Difference pressure between atria, ventricles and arteries Valves status: opened or closed Change of volume in ventricular chambers Direction of blood flow SECTON VI CIRCULATION Chapter 9~11 2009-09

11.2 MECHANICAL EVENTS OF THE CARDIAC CYCLE 11.2.2 Atria systole Events in late diastole The mitralis and tricuspid are opened and the aortic and pulmonary valves are closed Blood flows: into the heart from caval vein, filling the atria and ventricles Pressure in the ventricles remains low SECTON VI CIRCULATION Chapter 9~11 2009-09

11.2 MECHANICAL EVENTS OF THE CARDIAC CYCLE Atria systole Atrial systole starts after the P wave of the ECG Propels some additional blood into the ventricles Vena cava and pulmonary veins narrowed Vome regurgitation of blood into the veins during atrial systole SECTON VI CIRCULATION Chapter 9~11 2009-09

11.2 MECHANICAL EVENTS OF THE CARDIAC CYCLE 11.2.3 Ventricular systole Ventricular systole starts near the end of the R wave and ends just after the T wave of the ECG Isovolumetric ventricular contraction lasts about 0.05 s Mitral and tricuspid (AV) valves all closed Intraventricular pressure rises sharply as the myocardium presses on the blood No blood into or out the ventricles SECTON VI CIRCULATION Chapter 9~11 2009-09

11.2 MECHANICAL EVENTS OF THE CARDIAC CYCLE Ventricular ejection the ventricular pressures exceed aorta (80 mm Hg; 10.6 kPa) and pulmonary artery (10 mm Hg) The aortic and pulmonary valves open Propels blood into the large arteries more rapidly SECTON VI CIRCULATION Chapter 9~11 2009-09

11.2 MECHANICAL EVENTS OF THE CARDIAC CYCLE 11.2.4 Ventricular diastole Isovolumetric ventricular relaxation Ventricular pressure continues to drop rapidly The aortic and pulmonary valves are closed Ventricular filling Pressure falls below the atrial pressure the AV valves open, permitting the ventricles to fill SECTON VI CIRCULATION Chapter 9~11 2009-09

11.2 MECHANICAL EVENTS OF THE CARDIAC CYCLE 11.2.5 Heat sounds 1st sounds: 0.15 s, 25-45 Hz Myocardium contraction Flow impacting the cardiac wall Vibration set up by closure of A-V valves 2nd sounds: 0.12 s, 50 Hz. Vibrations associated with closure of arterial valves Arterial roots vibration SECTON VI CIRCULATION Chapter 9~11 2009-09

11.3 CARDIAC OUTPUT 11.3.1 Cardiac output in various conditions Stroke volume & ejection fraction Cardiac output (CO, minute cardiac output) CO=Stroke volume × Heart rate CO=70mL/beat×72/min=5.0L/min Cardiac index=CO/m2 SECTON VI CIRCULATION Chapter 9~11 2009-09

11.3 CARDIAC OUTPUT 11.3.2 Factors controlling cardiac output Control of stroke volume：the major factors influencing force of contraction Intrinsic regulation: the Frank-Starling mechanism Venous flow returned →changes in end-diastolic volume →heterometric autoregulation SECTON VI CIRCULATION Chapter 9~11 2009-09

11.3 CARDIAC OUTPUT Extrinsic regulation: sympathetic stimulation, epinephrine To increase myocardial contractility (inotropic status)→ the force of contraction at any given end-diastolic volume → hotmometric regulation SECTON VI CIRCULATION Chapter 9~11 2009-09

11.3 CARDIAC OUTPUT Afterload: the arterial pressures Against which the ventricles pump Increasing pressures decrease the strength of contraction SECTON VI CIRCULATION Chapter 9~11 2009-09

11.3 CARDIAC OUTPUT Control of heart rate Cardiac nerves Epinephrine Parasympathetic nerves (Cardiac Vagus) :  heart rate Sympathetic nerves:  heart rate Epinephrine  heart rate SECTON VI CIRCULATION Chapter 9~11 2009-09

11.4 CARDIAC RESERVE During exercise CO →20~25L/min→35L/min Heart reserve Stroke volume reserve Systolic reserve Diastolic reserve SECTON VI CIRCULATION Chapter 9~11 2009-09

Pumping procedure Atria systole and diastole Ventricular systole Isovolumetric ventricular contraction Ventricular ejection Ventricular relaxation Isovolumetric ventricular relaxation Ventricular filling SECTON VI CIRCULATION Chapter 9~11 2009-09

SECTON VI CIRCULATION Chapter 9~11 2009-09