Mechanisms of norepinephrine -increase Nat cazt permeability 个, phase4 spontaneous depolarization个, autorhythmicity↑ Ca2 influx↑, phase0 amplitude& velocity个, conductivity个 Ca2 influx个,Ca2 release↑,[Ca2+]个, contractility个Mechanisms of norepinephrine —increase Na+ & Ca2+ permeability • I f , phase 4 spontaneous depolarization, autorhythmicity  • Ca2+ influx , phase 0 amplitude & velocity , conductivity  • Ca2+ influx , Ca2+ release , [Ca2+ ] i , contractility 