[医学]心肌细胞电生理.ppt

* Electrical activities of heart Working cell Autorhythmic cell excitability conductivity contractility excitability conductivity contractility automaticity atrium AV node preferential pathway Bundle of His Left and right branch Purkinje fibers Ventricles SA node AV node Bundle of His Purkinje fibers SA node Dominant pacemaker Latent pacemaker ectopic pacemaker 1 Electrical activities of working cells (1) Resting potential (RP) a. most permeable to K+, relatively impermeable to other ions b. [C0][Ci] Inward rectifying K+ channels, Ik1 Na+ pump -90 mV 2K+ 3Na+ Na+ pump Na+-Ca2+ exchanger (NCE) Na+ background current Na+ 2K+ 3Na+ 3Na+ Ca2+ Na+ pump NCE Inward rectifying K+ channels, Ik1 Inward rectifying hyperpolarization Inward K+current depolarization Less outward K+current -90mV -100mV -80mV -20 mV: close Regulation Inward rectifying Mg2+ and polypeptides Blocking Remove under hyperpolarization Mg2+ Extracellular K+ Increase sensitivity to Mg2+ ischemia Decrease in Na+ pump activity Increase in [K+]o depolarization RP of atrial myocytes compared to ventricular cells a. Lower density of Ik1 b. acetylcholine-dependent K+ channel, IK-ACh -80 mV Parasympathetic nerve +30 -90 Phase 0: -90 to +30 Phase 1: +30 to 0 Phase 2: 0 Phase 3: 0 to -90 Phase 4: -90 (2) action potential (AP) Phase 0: -90 to +30 Fast Na+ channel open Na+ inflow Ik1 close a b 4 transmembrane domains 6 a helix：S1-S6 Fast Na+ channel S4: voltage sensor Positive charge P-loops：between S5 and S6，ion selection TTX binding site Voltage-dependent -100 mV:close Depolarization:open resting activation inactivation Activation gate Inactivation gate close open open open open close N-type inactivation: ball and chain model C-type inactivation Long Q-T syndrome Phase 1: +30 to 0 Na+ channel close Transient outward K+ channel，Ito1 Time and voltage-dependent a. Activation gate and inactivation gate b. Activation: -30mV Ito2 Ca2+-activated Cl- channel, CACC Activated by intracellular Ca2+ Time-depend