Cardiac Electrophysiology Qang×A(夏强),PhD Department of Physiology School of medicine Te:88206417,88208252 Email:xiaqiang@zju.edu.cn
Cardiac Electrophysiology Qiang XIA (夏强), PhD Department of Physiology School of Medicine Tel: 88206417, 88208252 Email: xiaqiang@zju.edu.cn
The major types of cardiac muscle Atrial muscle Contractile cells Ventricular muscle (收缩细胞) Specialized excitatory and conductive muscle Autorhythmic cells (自律细胞)
• The major types of cardiac muscle: – Atrial muscle – Ventricular muscle – Specialized excitatory and conductive muscle Contractile cells （收缩细胞） Autorhythmic cells （自律细胞）
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Sup Atrioventricular node vena cava Bundle of his Sinoatrial node Left atrium Right atrium Right bundle branch Left entricle Right ventricle Purkinje fibers Inferior vena cava Interventricular Left bundle branch sept Conducting system of the heart
Conducting system of the heart
Copyright e The MeGraw-Hill Companies, Inc. Permission required for reproduction or display. Striations Cardiac muscle Nt uCleus Intercalated discs (a) Intercalated discs Gap Junction Mitochondrion Cardiac muscle junction Sarcolemma Connexon Adjacent cell membranes
Cardiac muscle
Sequence of cardiac excitation Copyright@ The McGraw-Hill Companies, Inc. Permission required for reproduction or display Atrial excitation Ventricular excitation Ventricular relaxation Begins Complete SA node AV node Atrial Time Time Time Time Time The sinoatrial node is The Bundle of His and other parts the hearts pacemaker of the conducting system deliver because it initiates the excitation to the apex of the each wave of excitation heart so that ventricular contraction with atrial contraction occurs in an upward sweep
The sinoatrial node is the heart’s pacemaker because it initiates each wave of excitation with atrial contraction. The Bundle of His and other parts of the conducting system deliver the excitation to the apex of the heart so that ventricular contraction occurs in an upward sweep. Sequence of cardiac excitation
General process of excitation and contraction of cardiac muscle Initiation of action potentials in sinoatrial node Conduction of action potentials along specialized conductive system Excitation-contraction coupling Muscle contraction
General process of excitation and contraction of cardiac muscle • Initiation of action potentials in sinoatrial node • Conduction of action potentials along specialized conductive system • Excitation-contraction coupling • Muscle contraction
Transmembrane SAN potentials recorded in different heart AVN regions BH PF TPF 300600ms
Transmembrane potentials recorded in different heart regions
Transmembrane potential of ventricular cells and its ionic mechanisms Resting Potential: -90 mV 2 Action potential 0 Phase 0: Depolarization E-20 Phase 1: Early phase of rapid repolarization Phase2: Plateau(平台期) Phase 3: Late phase of rapid repolarization 4 Phase 4: Resting phase 100 50050100150200250 Time(msec)
Transmembrane potential of ventricular cells and its ionic mechanisms Resting Potential: -90 mV Action Potential • Phase 0: Depolarization • Phase 1: Early phase of rapid repolarization • Phase 2: Plateau（平台期） • Phase 3: Late phase of rapid repolarization • Phase 4: Resting phase
Ionic mechanisms Resting potential K equilibrium potential Nat-inward background current Extracellular space Electrogenic Na*-K pump [Na+ [C冂 K Na/K pump dNa Nongated Nongated K channel Nat channel Membrane Na* ATP [A] Cyt c[K+]
• Resting potential – K+ equilibrium potential – Na+ -inward background current – Electrogenic Na+ -K+ pump Ionic mechanisms
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. The action potential of a myocardial pumping cell ■ Phase0 a Threshold potential (-70mV) a Opening of fast Nat channel 口 Regenerative cycle(再生性循环 10.0 Opening of Na channels in membrane Pcaa(L) Decreased membrane Increased membrane 方1.0 potential (depolarization) Na’ permeability Increased flow of e Na’ into cell
◼ Phase 0 Threshold potential (-70mV) Opening of fast Na+ channel Regenerative cycle（再生性循环） The action potential of a myocardial pumping cell