基础医学各论：8.循环系统生理1

1、Cardiovascular Physiology （心血管生理学） Components of the cardiovascular system: Heart Vascular system Blood System Overview Plasma includes water, ions, proteins, nutrients, hormones, wastes, etc. The hematocrit is a rapid assessment of blood composition. It is the percent of the blood volume that is co

2、mposed of RBCs (red blood cells). The heart is the pump that propels the blood through the systemic and pulmonary circuits. Red color indicates blood that is fully oxygenated. Blue color represents blood that is only partially oxygenated. The distribution of blood in a comfortable, resting person is

3、 shown here. Dynamic adjustments in blood delivery allow a person to respond to widely varying circumstances, including emergencies. Functions of the heart Pumping（泵血） Endocrine（内分泌） Atrial natriuretic peptide (ANP) Brain natriuretic peptide (BNP) Other bioactivators The major external and internal

4、parts of the heart are shown in this diagram. The black arrows indicate the route taken by the blood as it is pumped along. The Heart Valves of the heart The general route of the blood through the body is shown, including passage through the heart (colored box). The major types of cardiac muscle: At

5、rial muscle Ventricular muscle Specialized excitatory and conductive muscle Contractile cells （收缩细胞） Autorhythmic cells （自律细胞） Conducting system of the heart Cardiac muscle The sinoatrial node is the hearts pacemaker because it initiates each wave of excitation with atrial contraction. The Bundle of

6、 His and other parts of the conducting system deliver the excitation to the apex of the heart so that ventricular contraction occurs in an upward sweep. Sequence of cardiac excitation General process of excitation and contraction of cardiac muscle Initiation of action potentials in sinoatrial node C

7、onduction of action potentials along specialized conductive system Excitation-contraction coupling Muscle contraction Click here to play the Conducting System of the Heart Flash Animation (250-300 bpm) (350-600 bpm) Scaling from the level of the organelle to the organ Transmembrane potentials record

8、ed in different heart regions Transmembrane potentials in epicardium and endocardium Transmembrane potential of ventricular cells and its ionic mechanisms Resting Potential: -90 mV Action Potential Phase 0: Depolarization Phase 1: Early phase of rapid repolarization Phase 2: Plateau（平台期） Phase 3: La

9、te phase of rapid repolarization Phase 4: Resting phase Resting potential K+ equilibrium potential Na+-inward background current Electrogenic Na+-K+ pump Ionic mechanisms n Phase 0 p Threshold potential (-70mV) p Opening of fast Na+ channel p Regenerative cycle（再生性循环） The action potential of a myoca

10、rdial pumping cell. n Phase 1 p Transient outward current, Ito K+ current pactivated at 20 mV popening for 510 ms n Phase 2 Inward currentOutward current (Ca2+ Na+ channels (purple) and Ca2+ channels (yellow) mediate Na+ and Ca2+ influx, respectively. The Na+/Ca2+ exchanger (red) is electrogenic, as

11、 it transports three Na+ ions for each Ca2+ ion across the surface membrane. b, Ionic currents and genes underlying the cardiac action potential. Top, depolarizing currents as functions of time, and their corresponding genes; centre, a ventricular action potential; bottom, repolarizing currents and

12、their corresponding genes. From the following article: Cardiac channelopathies Eduardo Marbn Nature 415, 213-218(10 January 2002) doi:10.1038/415213a Click here to play the Action Potential in Cardiac Muscle Cell Flash Animation Transmembrane potentials recorded in different heart regions Transmembr

13、ane potential of autorhythmic cells and its ionic mechanisms Contractile cellsAutorhythmic cells Phase 4 stable potentialPhase 4 spontaneous depolarization （4期自动去极化） Resting potentialMaximal repolarization potential （最大复极电位） Purkinje cells: Fast response autorhythmic cells 4 Ionic mechanism Phase 03

14、：similar to ventricular cells Phase 4： (1) If Funny current, Pacemaker current（起搏电流） (2) Ik Decay（钾电流衰减） Characteristics of If channel Na+, K+ Voltage- this effect tends to disappear when levels reach 7-9 mEq/L. Sinus arrest may occur when the serum potassium level reaches about 7.5 mEq/L, and cardi

15、ac standstill or ventricular fibrillation may occur when serum levels reach 10 to 12 mEq/L. Periodic changes in excitability Postrepolarization refractoriness of slow response cells Valuable protective mechanism nThe long refractory period means that cardiac muscle cannot be restimulated until contr

16、action is almost over 2.critical timing; 3.the length of the effective refractory period of the normal tissue. Q-T interval recorded on an ECG primarily corresponds to: A Ventricular repolarization B Ventricular depolarization plus ventricular repolarization C Ventricular depolarization and atrial repolarization D Atrial depolarization and conduction through AV node E Purkinje fibers repolarization The resting membrane potential of a sinus nodal fiber is A -124 mV B -91 mV C -85 mV D -55 mV E -25 mV You see a 55-year-old, white female for a routine check-up