效应:释放Ach,作用于心肌细胞膜上M受体,引起cAMP 浓度降低,导致: 1.心率减慢,负性变时作用; (抑制I促进复极时钾外流) Parasympathetic stimulation igure 17-13 The transmembrane potential changes(A)that occur in SA ells are produced by the following currents(B): ie. (block), i(red). o Fleshandbones com Davies et al: Human Physiology ind.(blue).(Redrawn from Broun HF: Physiol Rev 61:644, 1981)效应: 释放 Ach,作用于心肌细胞膜上 M 受体,引起 cAMP 浓度降低，导致: 1.心率减慢，负性变时作用； （抑制If，促进复极时钾外流）