第一节心脏的生物电现象及节律性 兴奋的产生与传导 心肌组织的生理特性兴奋性传导性自律性收缩性 心肌细胞的分类: 工作细胞(普通心肌):心房肌细胞,心室肌细胞 自律细胞(特殊传导系统)起搏(P)细胞,浦肯野细胞 二种细胞的比较: 兴奋性传导性自律性收缩性 工作细胞 有有无 自律细胞 有有有无
第一·节 心脏的生物电现象及节律性 兴奋的产生与传导 心肌组织的生理特性：兴奋性 传导性 自律性 收缩性 心肌细胞的分类： 工作细胞（普通心肌）：心房肌细胞，心室肌细胞 自律细胞（特殊传导系统）：起搏（Ｐ）细胞，浦肯野细胞 二种细胞的比较: 兴奋性 传导性 自律性 收缩性 工作细胞 有 有 无 有 自律细胞 有 有 有 无
Electrical Activity of the heart OBJECTIVES Explain the types of cardiac action potentials. Define the ionic basis of cardiac action potentials. Explain the temporal changes in cardiac excita bility 心肌细胞的快反应动作电位和慢反应动作电位; 心肌细胞的电生理特性(传导性和兴奋性)
Electrical Activity of the Heart OBJECTIVES • Explain the types of cardiac action potentials. • Define the ionic basis of cardiac action potentials. • Explain the temporal changes in cardiac excitability. • 心肌细胞的快反应动作电位和慢反应动作电位； • 心肌细胞的电生理特性（传导性和兴奋性）
威廉.艾因特霍芬 (Willem einthoven) 荷兰生理学家威廉.艾因特霍芬 ( Willem einthoven,1860~1927)因对 心电图学的开创性工作和无与伦比的贡 献而被誉为“心电图之父”,并于1924 年获诺贝尔生理学或医学奖。 Willem einthoven
Willem Einthoven 威廉 . 艾因特霍芬 （Willem Einthoven） 荷兰生理学家威廉 . 艾因特霍芬 （ Willem Einthoven, 1860~1927 ） 因对 心电图学 的 开创性工作和无与伦比的贡 献 而 被誉为“心电图之父”，并于1924 年获 诺贝尔生理学或医学奖
Cardiac Transmembrane Potentials are Prolonged The electrical behavior of -SAN (005) cardiac cells differs considerably AM (0.4) from that of nerve cells or of AVN (002) smooth or skeletal muscle ceils in (0.2) general, the durations of action potentials are much longer in (20) cardiac cells than in nerve cells or (40) in smooth or skeletal muscle cells VM (10) The action potentials differ 0300600 substantially among various 时间(ms) type of cardiac cells depending 图4-5心脏各部分心肌细胞的 跨膜电位和兴奋传导速度 on the function and location of sAN:窦房结AM:心房肌AMN:结区BH1希氏束 PF:浦肯野纤维TPF末梢浦肯野纤维VM:心室肌 those cells 传导速度单位m/s
Cardiac Transmembrane Potentials are Prolonged The action potentials differ substantially among various type of cardiac cells depending on the function and location of those cells. The electrical behavior of cardiac cells differs considerably from that of nerve cells or of smooth or skeletal muscle ceils. in general, the durations of action potentials are much longer in cardiac cells than in nerve cells or in smooth or skeletal muscle cells
he potential charge recorded from ventricular muscle cell Resting potential -90 mv (interior is lower than that of the surrounding medium) Action potential Phase: the rapid upstroke of the action potential depolarizes from -90mv to +2030 mV; Phase 1: a brief period of partial repolarization Fast response +20mV→>0mV, Phase 2:a plateau( persists for about 0. 2 second).ao 3 It is main difference 80 comparing with nerve and skeleton muscle cells 120 0100200300
Action potential: Phase 0 : the rapid upstroke of the action potential. depolarizes from -90mV to +20～30 mV; Phase 1 ：a brief period of partial repolarization +20 mV → 0 mV, Phase 2 ：a plateau ( persists for about 0.2 second). the potential charge recorded from ventricular muscle cell Resting potential ： - 90 mV (interior is lower than that of the surrounding medium) It is main difference comparing with nerve and skeleton muscle cells
Phase3: repolarization This proceeds more slowly than dose depolarization(phase 0). Phase 4: The interval from the completion of repolarization until the beginning of the next action potential Fast response 膜电位 AP 0 -80 b 4 ERP 100200300
Phase 3 ：repolarization This proceeds more slowly than dose depolarization (phase 0). Phase 4 : The interval from the completion of repolarization until the beginning of the next action potential
Action potential occurs well before the contractile force attains its peak, and repolarization is completed well before the cell reaches its full resting value. The relaxation of the cardiac muscle takes place mainly during phase 4 of the action potential Action potential Contractile force Time FIGURE 16-2. Relationships between the developed force and the changes in transmembrane potential in a thin strip of ventricular muscle.(Redrawn from Kavaler F, Fisher VI Stuckey JH: Bull N Y Acad Med 41: 592, 1965
Action potential occurs well before the contractile force attains its peak, and repolarization is completed well before the cell reaches its full resting value. The relaxation of the cardiac muscle takes place mainly during phase 4 of the action potential
There are two principal Types of Cardiac Action Potentials Fast-response action potentials: occurin atrial and ventricular myocardiac fibers and specialized conducting fibers(purkinje fibers) that exist mainly in the endocardiac surfaces of the ventricles Slow-response action potentials: occur in the sinoatrial (SA)node(sA), which is the natural pacemaker region of the heart and the atrioventricular(Av) node, which is the specialized tissue that conducts the cardiac impulse from he atria to the ventricles
• Fast-response action potentials: occur in atrial and ventricular myocardiac fibers and specialized conducting fibers (Purkinje fibers) that exist mainly in the endocardiac surfaces of the ventricles. • Slow-response action potentials: occur in the sinoatrial (SA) node (SA), which is the natural pacemaker region of the heart; and the atrioventricular (AV) node, which is the specialized tissue that conducts the cardiac impulse from the atria to the ventricles. There Are Two Principal Types of Cardiac Action Potentials
Comparing with the fast-response action potential: The resting membrane of slower-response is considerable less negative, a bout -50 mV The slop of the upstroke(phase 0), the amplitude and overshoot of the action potentials are less; (amplitude of action potential and the rate of rise of the upstroke are important determinants of the conduction velocity). 40 Fast response Slow response 0 2 -40 b c ERP RRP 120 ERP 0100200300 100200300 Time(msec)
Comparing with the fast-response action potential: The resting membrane of slower-response is considerable less negative, about -50 mV; The slop of the upstroke (phase 0), the amplitude and overshoot of the action potentials are less; （amplitude of action potential and the rate of rise of the upstroke are important determinants of the conduction velocity)
Fast responses may change to slow responses under certain pathological conditions, for example, in coronary artery disease A B C 0 mV K=3 mM K+=7 K+=10 50 msec E H 20 mV 0 mV St K+=14 K+=16 K+=3 FIGURE 16-3. Effect of changes in external [K+] on the transmembrane action potentials recorded from a Pur- kinje fiber The stimulus artifact (St)appears as a bipha- sic spike to the left of the upstro
Fast responses may change to slow responses under certain pathological conditions, for example, in coronary artery disease
