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