心泵

1、Chapter 10 The heart as a pump,,Section 1 The contractility of the heart,,The ultrastructure of cardiac muscleSarcomere is similar with skeletal muscleIntercalated disks, gap junctions between cellsRich in m

2、itochondriaUnder-developed sarcoplasmic reticulum (SR), contraction is dependent on [Ca2+]o (CICR),,2. The excitation-contraction coupling of cardiomyocyteThe process which connects excitation and contractionTriggere

3、d by Ca2+ influxCICR, Ca2+ transientCardiocyte contraction induced by Ca2+Ca2+ reuptake and relaxation: Ca2+ pump of SR,,Membrane potential,ICal current,Ca2+ transient,Cell shortening,Excitation-contraction of cardiom

4、yocyteAction potential of cardiomyocyte?Ca2+ influx via L-type Ca2+ channel?Ryanodine receptor of SR?CICR,Ca2+ release of SR?Ca2+ binds to troponin?Myofilament sliding?Cardiocyte contraction,The characterist

5、is of heart contraction1. Dependence on [Ca2+]o Source of sachoplasmic Ca2+: ICal (Ca2+ influx) (10%) CICR: Calcium-induced calcium release (Ca2+ influx stimulates ryanodin

6、e receptor) (90%) 2. “All or none” contraction (全或無(wú)式收縮） The atrium and ventricle are two functional syncytia (機(jī)能合胞 體）, just like two cells. 3. No complete tetanus (不產(chǎn)生完全強(qiáng)直收縮) ERP is very

7、long, the heart is non-responsive to any stimulus during contraction and early relaxation.,,Section 2 The pumping function of the heart,,Cardiac cycle （心動(dòng)周期）The cardiac events that occur from the beginning o

8、f one heartbeat to the beginning of the next are called cardiac cycle.Each cycle is initiated by spontaneous generation of an action potential in the sinus node.The conduction delay in the A-V node (>1/10sec) allows

9、 the atria to contract ahead of the ventricles, thereby pumping blood into the ventricles before the strong ventricular contraction begins. Thus, the atria act as primer pumps (初級(jí)泵） for the ventricles.,,The characteristi

10、cs of a cardiac cycle Diastole is longer than systole Heart rate mainly affects diastole,Time sequence of the events in a cardiac cycleAtrial systole?Ventricular systoleIsovolumic contraction phaseRapid ejec

11、tion phaseReduced ejection phase?Ventricular diastoleIsovolumic relaxation phaseRapid filling phaseReduced filling phase,,Figure 10-3 Events of the cardiac cycle for LV function, showing changes in LA pressure, LV

12、 pressure, aortic pressure, ventricular volume, ECG, and the phonocardiogram.,Function of atria as primer pumpsAtrial contraction usually causes an additional 25% filling of the ventricles; 75% of the blood flows direc

13、tly through atria into the ventricles.The heart usually can continue to operate even the atria stopping work unless a person exercises.,,Heart sound （心音）The first heart sound: represents the beginning of ventricular c

14、ontraction.The second heart sound: represents the beginning of ventricular dilation.The third heart sound: heard at the end of ventricular rapid filling, caused by the vibration of ventricular wall and papillary muscle

15、, found in some children, young people and HF. Gallop rhythm (奔馬律): all the above 3 sounds appear.The forth heart sound (atrial sound): heard before the first heart sound, caused by atrial contraction and ventricular fi

16、lling, usually can not be heard, found by phonocardiogram at the decrease of ventricular wall compliance.,,Cardiac murmur （心臟雜音）Systolic murmurDiastolic murmur Phonocardiogram （心音圖）,,Section 3 The evaluation o

17、f cardiac pumping function,,Stroke volume （每搏輸出量）The blood output in each contraction of LV or RV, about 70ml at resting condition in an healthy adult. Ejection fraction （射血分?jǐn)?shù)，EF） Minute volume (cardiac output)

18、　（每分輸出量, 心輸出量） Cardiac output = stroke volume ? heart rate,,Cardiac index （心臟指數(shù)）,,CI: 10 years old: 4 normal adult ≥ 3 80 years old 2,Stroke work （每搏功，搏功）　Stroke work (J) = stroke volume

19、 (L) ? ejection pressure + kinetic energy of blood flow,,心臟作功量心室收縮一次所做的機(jī)械功稱為搏功W=∫ PdV（壓力-容積功 ） ＋∑1/2v2dm （動(dòng)力功） V2為舒張期末容量， V1為收縮期末容量 ，P為心室內(nèi)壓，V為心室容量 v為血流速度，m為射出血液的質(zhì)量

20、 W=PV＋1/2mv2 P為主動(dòng)脈平均血壓，V 為每搏輸出量， v為平均血流速度 劇烈運(yùn)動(dòng)時(shí)m和v顯著增大，

21、 動(dòng)力功不能忽略 W=PV,v2v1,,,心臟作功效率（外功/心臟耗氧量） 心臟消耗內(nèi)能（主要通過有氧代謝） ? 外能 ? 熱（降低作功效率）

22、 ? ? 功 ? 內(nèi)功（非有用功： 等容收縮、心率過快等） ? 外功（和泵血直接有關(guān)的有用功） 容量功：內(nèi)功所占比例低，效率高壓力功：內(nèi)功所占比例高，效率低 如動(dòng)脈壓升高，心室擴(kuò)大,,Section 4 Cardiac Reserve,,The capacity of card

23、iac output of a healthy adult:At rest: 5 L/minMaximum: 25-30 L/minMaximum of a well-trained athlete: 35 L/min,,The components of cardiac reserve Stroke volume reserve: At rest: 70 ml Maximum: 105-110

24、 ml (including end diastolic volume reserve 25 ml, end systolic volume reserve 15-20 ml)Heart rate reserve Maximal HR: 160-180 beats/min Too fast HR will decrease the cardiac output,,Section 5 Factors that

25、 affect cardiac pumping function,,Preload （前負(fù)荷）Cardiac preload can be reflected by the ventricular end diastolic pressure, or, initial length (初長(zhǎng)度）.Heterometric autoregulation (Frank-Starling mechanism of the heart) (

26、異長(zhǎng)自身調(diào)節(jié)）：　The greater the heart muscle is stretched during filling, the greater the force of contraction and the greater the quantity of blood pumped into the aorta. In other words, within the physiologic limits

27、, the heart pumps all the blood that comes to it without allowing excessive damming of blood in the veins.,,Ventricular function curve reflects the relationship between preload and pumping function.,The curves do not ha

28、ve downward branch,The mechanisms of Frank-Starling law: (1) The effective overlapping degree of thick filaments and thin filaments of the sarcomere; (2) The affinity of troponin to Ca

29、2+ depends on the length of muscle.,,The preload is affected by venous retuning volume and end systolic ventricular volume: Four factors determine the venous retuning volume: ventricular filling ti

30、me venous blood retuning speed The pressure of pericardial cavity The compliance of the ventricle,,Afterload （后負(fù)荷）Cardiac afterload can be reflected by the stretching force of the ventr

31、icular wall at systole, or the peripheral resistance (外周阻力）.An increase in afterload will decrease cardiac output,,Cardiac contractility （心肌收縮能力）An intrinsic factorAffected by neurohormonal factorsIndependent of

32、pre- or afterload,,Heart rate （心率）,,,,,,,正常心臟,心臟擴(kuò)大,Role of atria in the pumping funtion of heart1. As a tract of blood returning Increased ventricular pressure Dysfunction of at

33、rial contraction Decrease in atrial compliance ↓ Decrease in veinous blood retuning