PHASEO OF THE FAST FIBER ACTION POTENTIAL Na B -90mv 65mv D Omy +20mv Chemical Na Gradient E Electrical +30mv Gradient
27 PHASE 0 OF THE FAST FIBER ACTION POTENTIAL h m Na+ -90mv A Na+ m h -65mv B m h Na+ 0mv C m h Na+ D +20mv Na+ m h +30mv E Chemical Gradient Electrical Gradient
Ion channels in ventricular Muscle Inactivating K channels(ITO Ultra-rapid'K channels (K Rapid k channels(Ikr) Voltage-gated Slow K channels(I Na Channels Voltage-gated Ca channels 200 msec 28
28 Ion Channels in Ventricular Muscle Ventricular muscle membrane potential (mV) -50 0 200 msec Inactivating K channels (ITO) “Rapid” K channels (IKr) “Slow” K channels (IKs) IK1 Voltage-gated Na Channels “Ultra-rapid” K channels (IKur) Voltage-gated Ca Channels
Ion Channels in Ventricular Muscle Current Na Current Ca Current TO Kr 29
29 Ion Channels in Ventricular Muscle Current Na Current Ca Current IK1 ITO IKur IKs IKr
2. Transmembrane Potentiate Rhythmic Cers 30
30 2. Transmembrane Potential of Rhythmic Cells
lon Channels in Purkinje Fibers 30 At phase 4, the membrane potential do loes not maintain at a level na but depolarizes automatically K+outward flow the automaticity >(Phase0-3)Same as for ventricular cells (Phase 4)Plus a very small amount of If 31 pacemaker) channels
31 Ion Channels in Purkinje Fibers ➢ At phase 4, the membrane potential does not maintain at a level, ➢ but depolarizes automatically – the automaticity ➢ (Phase 0 – 3) Same as for ventricular cells ➢ (Phase 4) Plus a very small amount of If (pacemaker) channels