生理复习---血液循环(英文版)

Chapter4 cardiovascular system

Section one Pump function of heart

I. Cardiac Cycle

c cycle:The period of one contraction and one relaxation of the

heart.

c cycle＝60s／heart rate;heart rate:75beats/min,so cardiac cycle

is 0.8sec.

3.A cardiac cycle consists of a systole(收缩期) and a diastole(舒张期).When

heart beat becomes more rapid, the heart cycle is shorter, and the diastole

is much shorter than normal.

cular systole:isovolumic contraction(Enable the ventricular

pressure to rise from 0 to the level of aortic pressure)，rapid ejection，slow

ejection.

cular diastole:isovolumic relaxation(Enable the ventricular pressure

fall to the level near the atrial pressure),rapid filling,slow filling,atrial

systole.

sound

(1)first sound:caused by closure of the atrioventricular valves,marks the

beginning of ventricular systole.

(2)second heart sound:caused by closure of the aortic and pulmonary

valves,marks the beginning of ventricular diastole.

II. Cardiac Output

volume

(1)concept:The amount of blood pumped out of each ventricle per beat

is called the stroke volume, about 70mL in a resting adult.

(2)stroke volume(70mL)＝end-diastolic volume(125)－end-systolic

volume(55mL)

on fraction(55%~65%)＝stroke volume(70mL)／end-diastolic

volume(125mL)

c output(心输出量)

(1)The output of each ventricle per minute is called the cardiac output.

(2)It varies with sex,age,and 4.5~6.0L/min in a resting

healthy man.

c index(心指数)

(1)concept:The output per minute per square meter of body surface is

known as the cardiac index.

(2)the normal range is: 3.0 – 3.5 L/min·m2

III. Factors Affecting Cardiac Output

①Preload(前负荷),②Afterload(后负荷),③myocardinal

contractility(心肌收缩能力),④heart rate.

d(前负荷)------ventricular end-diastolic volume(心室舒张末期容积)

(1)end-diastolic volume↑→initial length in cardiac muscle↑→contractility↑→stroke volume↑.

(2)optimal initial preload(length) is 2.0~2.2µm.

(3)factors determining the preload:①blood volume of venous return(静脉回心血量)：Period of the ventricle diastole(充盈时间)，Speed of the venous

return(静脉回心速度)，pericardial fluid(心包积液)，ventricular compliance(心室顺应性).②Ventricular residual blood volume after contraction(射血后心室内的剩余血量).

oad(后负荷)------arterial pressure(大动脉血压)

afterload↑→period of isovolumic contraction↑,period of ejection↓→stroke

volume↓→heterometric regulation(异长调节)→end-diastolic volume↑→preload↑→stroke volume↑(恢复正常).

dinal contractility(心肌收缩能力)

(homometric regulation)

Factors determining the myocardinal contractility:①numbers of activated

cross bridge,②Ca2+ concentration,③ATPase activity.

rate

(1)heart rate ↑→cardiac output ↑(40—180beats/min)

(2)heart rate > 160—180beats/min or heart rate <40beats/min

=>cardiac output ↓

c reserve(心力储备)

Concept:The capacity of the heart to increase cardiac output to satisfy

human metabolic needs is called cardiac reserve.

Section Two Electrical Activity of the Heart

cardiac muscle cell has four physiological properties：excitability,

automaticity, conductivity and contractility.

embrane potential of working cell

g potential(静息电位)

Mechanism:(1)K+ outward current,IK1,-90mV.

(2)Na+ inward backround current(钠背景电流)

potential(动作电位)

divided into 5 phases：Phase0，Phase1，Phase2，Phase3，Phase4

(1)Phase0(rapid depolarization):Na+ influx into cell,INa

fast

channel(Activated and inactivated very fast,Voltage dependent,Blocked by

TTX).

(2)Phase1(rapid initial repolarization):K+ transient outward current ,Ito(钾一过性外向电流).

(3)Phase2(plateau):①Ca2+ inward current(L-type),②K+ outward current(Ik,延迟整流钾流).-----Inward Ca2+ current＝outward K+ current at early stage

of plateau.

(4)Phase3(rapid late repolarization):①K+ efflux via IK channel,②K+ efflux

via IK1 channel.

(5)Phase4(resting membrane potential):①Na+-K+

pump:3 Na+ out and 2 K+ in,②Na+-Ca2+ exchange:1 Ca2+ out and 3 Na+ in,③Ca2+

pump: 1 Ca2+ out of cell.

embrane potential of Rhythmic cell

Feature:Phase 4 spontaneous depolarization

potential of P cell

Mechanism:(1)Phase0:Ca2+ influx,ICa-L channel

(2)No distinct phase 1 and phase 2.

(3)Phase3:K+ efflux,IK

channel

(4)Phase4:①IK declines and K+ efflux decreases*

②Inward current, If ↑（Na+）