RP, AP of cardiac cellsPacemakerAPVentricularAPKchannelsopen0-0T-Type Ca2*channelsopen25-25--50-50-L-Type Ca2*-75-75Slow Nat leakchannels open-100--100-300 ms300msNatCa2* (L)K*eaCa2* (L)K*Ca?* (T)Na'(f)
RP, AP of cardiac cells
I.Restingpotential(RP)VentricularAP(1) Magnitude: -90mV0-(largerthanskeletal muscle-25cells and neurons)-50-(2) Mechanism : [K*]-75-equilibriumpotential.-100300ms- K+ equilibrium potential-Nat-inward background current- Electrogenic Nat-K+ pump
（1）Magnitude：- 90mV (larger than skeletal muscle cells and neurons). I．Resting potential (RP) （2）Mechanism ：[K+ ] equilibrium potential. – K+ equilibrium potential –Na+ -inward background current – Electrogenic Na+ -K+ pump
Qualifications:lon concentration differences exist betweenextracellularand intracellularfluids[K+]; > [K+]。=28: 1[Na']; <[Na']。=1: 13Selective Permeability of ions:K+/Nat=100/1Results:K+ reach its equilibrium potential.K+ diffusebecause of itsconcentrationdifference
Qualifications： Ion concentration differences exist between extracellular and intracellular fluids. Selective Permeability of ions： K+ / Na+＝100 / 1 [K+ ] i ＞ [K+ ]o ＝28: 1 [Na+ ] i ＜ [Na+ ]o ＝1: 13 Results：K+ reach its equilibrium potential. K+ diffuse because of its concentration difference
Il. Action potential (AP)Depolarization:0(Rapid depolarization)- 90 →+ 30 mvRepolarization:1: Brief repolarization+30→-0 mv. 10 msDepolarizationBriefrepolarization02 (plateau)①Plateau?mv, 100-150 ms03(repolarization)0Repolarization30 mv→ - 90 mv,100-150ms444 (RP)-90-90mv0200300400100Time (msec)
II. Action potential (AP) Repolarization: 2（plateau） 0 mv, 100-150 ms 4（RP） - 90 mv 0（Rapid depolarization） - 90 + 30 mv 1：Brief repolarization +30 - 0 mv, 10 ms 3（repolarization） 0 mv - 90 mv, 100-150 ms Depolarization:
1. Mechanism20（W）1Phase 021Stimulus608X300150Transmembrane potentiallTimeCms★Threshold (-70 mV)金Fast Na+ channels open★Nat influxPositivefeedbackfashionIt is activated at -7OmV.Lasts about 1-2 ms, only for Na+Na+ equilibrium potentialblocker: phenytoin sodium(0 phase)Lidocaine; Guinidine
1. Mechanism Stimulus ↓ Transmembrane potential↓ ↓ Threshold (-70 mV) ↓ Fast Na+ channels open ↓ Na+ influx Positive feedback fashion ↓ Na+ equilibrium potential （0 phase） It is activated at -70mV. Lasts about 1-2 ms, only for Na+ blocker: phenytoin sodium Lidocaine; Guinidine 按任意键显示动画2 Phase 0