上半

  • Anatomy of the heart
    心脏解剖学
    • location & size
      • The heart lies between the two lungs, just above the diaphragm隔膜
      • From child to adult, the heart is roughly the same size as the fist
      • weight about 300g
    • The pericardium心包 and heart wall
      peri- 外围的
      • 图
      • The heart is enclosed in a double-walled sac called the pericardium
      • The pericardium protects the heart, and allows it to beat with minimal friction
      • The heart wall consists of 3 layers: epicardium (心外膜), myocardium (心肌层) and endocardium (心内膜)
      • The myocardium is the thickest layer. It is composed of cardiac muscle, and performs the work of the heart.
    • The cardiac muscle
      • The cardiac muscle cells are arranged in spiral bundles
      • The plasma membrane at the end of the cardiac cell is folded like the bottom of an egg carton
      • Gap junctions are important components of the intercalated discs (闰盘)
      • The sarcoplasmic reticulum is less developed than in skeletal muscle; it forms a diad with the T tubule
  • RP&AP
    • The RP of cardiac muscle
      • The resting potential of cardiac working cell =-90mV
      • The inward rectifier K+ channel (内向整流IK1通道) contributes to the resting potential
      • rectifier整流通道类似单向门，ohmic欧姆通道两侧都能过
      • 让细胞静息电位保持在-90mV
    • The AP of cardiac muscle
      • 分类
        • 根据velocity of depolarization
          • fast response cell
            • rapid depolarization, large amplitude, slow repolarization with a plateau
          • slow response cell
            • slow depolarization, small amplitude, rapid repolarization without a plateau
        • 根据spontaneous depolarization
          • authorhythmic cell
            • self-excitation with rhythmical discharge, but can not contract
          • working cell
            • excited by autorhythmic cell, can contract
        • 根据以上两个分类
          • fast-response working cells: atrial心房 muscle and ventricular心室 muscle
          • slow-response autorhythmic cells: sinoatrial node窦房结 and atrioventricular node房室结
          • fast-response autorhythmic cells: Purkinje fiber, bundle of His, bundle branch
      • AP of ventricular muscle
        • 图
        • 过程
          • phase 0: depolarization, INa channels open, 1~2ms
            INa导致去极化
          • phase 1: initial repolazrization, INa channels close, Ito(transient outward current) channels open, 10ms
            K+通道Ito短暂开启复极化
          • phase 2: plateau, ICa-L (long-lasting) channels open and counter K+ efflux via IK1 and IK (delayed rectifier K+ current) channels, 100~150ms
            Ca2+与两种K+通道导致一段平台期
          • phase 3: rapid repolarization, ICa-L channels close, IK1 and IK increase 100~150ms
            Ca2+关闭，K+内向整流越来越快地复极化
          • phase 4: resting state, Na+-K+ pump, Ca2+ pump and Na+-Ca2+ exchanger together return the membrane potential to -90mV
            各种泵恢复静息电位
      • AP of atrial muscle
        • 相比于心室细胞，由于膜上表达通道蛋白不同，心房细胞平台期较短，静息电位为-80mV(Ik1表达较少)
      • AP of pacemaker cell
        • 与心室细胞相比
          • 图
          • lower resting potential – lack of Ik1
          • lower threshold potential阀电位 and smaller AP amplitude – lack of INa and ICa-L-dependent depolarization
            Ca2+导致去极化而不是Na+
          • no phase 1 – lack of Ito
          • no phase 2 – strong outward Ik can not maintain the balance of the plateau
        • spontaneous 自主性的原理
          • 图
          • Ik decline and If (hyperpolarization-activated inward current) activation in phase 4 leads to spontaneous depolarization.
            If，funny，在极化(-50mv)时候被激活
          • Ik decline is more important.
          • When the membrane potential depolarizes to -50mV, ICa-T occurs and then activates ICa-L
      • AP of Purkinje fiber
        • 快反应自主性
        • similar to the one of ventricular muscle
        • can depolarize spontaneously due to IK decline and If activation
        • If is fully activated at -100mV, and Purkinje fibers repolarize close to this level, thus If is more important
  • The electrophysiological properties of cardiac muscle
    • excitability
      • Factors
        • ①The difference between the resting potential / maximal repolarization potential and the threshold potential – small difference means high excitability
          静息电位与阀电位差距↓ excitability↑
        • ②The status of ion channels that depolarize the membrane potential
      • 各个时期
        • RP = refractory period
        • 绝对不应期ARP
        • 有效不应期ERP = ARP + LRP
        • 局部反应期LRP
        • 相对不应期RRP
        • 超常期SNP
    • conductivity
      • 细胞间通过intercalated discs闰盘传递AP
      • 过程
        • ①Action potentials originating in the sinus node spread through the entire atrial muscle mass and to the A-V node (房室结)
        • ②atrioventricular delay ( 房室延搁) allows time for the atria to empty their blood into the ventricles before ventricular contraction begins
        • ③Purkinje fibers lead from the A-V node through the A-V bundle (房室束) into the ventricles. They are very large fibers, and they transmit action potentials at a velocity about 6 times that in the ventricular muscle and 150 times that in some of the A-V nodal fibers
          浦肯野纤维连着末端的心室肌肉，传电速度超级快
        • 传播时间
      • Factors
        • ①Structural: fiber diameter, cell differentiation, numbers of gap junctions
        • ②Physiological: velocity and amplitude of depolarization in phase 0, excitability of adjacent cells
    • autorhythmicity
      • Discharge rates
        • sinoatrial(sinus) node, 70 times/min
        • A-V node, 50 times/min
        • Purkinje fiber, 25 times/min
      • The sinoatrial node controls the beat of the heart by
        • ① preoccupation (抢先占领)
        • ② overdrive suppression (超速驱动压抑)
  • Myocardial contraction
    心肌收缩
    • 相比于肌肉，心肌没有triad只有diad
    • 特点
      • ①Simultaneous contraction
        • all-or-none contraction.
        • The cardiac muscle fibers of atria and ventricles function as two syncytiums (合胞体) due to the intercalated discs.
      • ②Dependence of extracellular Ca2+
        • The sarcoplasmic reticulum in the cardiac muscle is less developed than in the skeletal muscle, providing only 80~90% Ca2+ for contraction
      • ③No tetanus强直收缩
        • Prolonged ERP lasts till muscle relaxation begins
          有效不应期到肌肉开始放松才结束
  • Electrocardiogram
    • P-QRS-T， depolarization，repolarization
    • P wave – atrial depolarization
    • QRS complex – ventricular depolarization
    • T wave – ventricular repolarization
    • PR interval – atrioventricular delay
    • QT interval – ventricular AP/ contraction
    • ST segment – plateau of ventricular AP
  • The heart as a pump
    • Internal anatomy of the heart
      • 右边连着静脉，左边连着动脉，肺动脉里是静脉血，肺静脉里是动脉血
      • arteries动脉，veins静脉，pulmonary肺，aorta主动脉，capillary毛细血管，atrium心房，ventricle心室
      • 右心室是个月亮，左心室是个圆
      • The atrioventricular valves房室瓣 are anchored to the papillary乳突的 muscles of the ventricle by the chordae tendineae (腱索)
      • 左侧semilunar (SL) valves半月瓣 closed, atrioventricular valves open 右侧相反
      • 右边的房室瓣atrioventricular valve是三尖瓣tricuspid valve，左边的房室瓣atrioventricular valve是双尖瓣bicuspid valve = mitral valve
    • The cardiac cycle
      • 右心室压力变化比左心室小
      • systole收缩，diastole舒张，心跳变快时候，舒张时间显著减少
      • 看图说话环节，下面蓝色的是ventricular systole，红色的是ventricular diastole，Pao动脉压力，Pv心室压力，PA心房压力
      • 心房收缩期atrial systole
        • the end of ventricular diastole
        • 心房和心室压力缓慢增加
        • 心房压力大于心室压力，bicuspid valve打开，1/3的体积流入心室
        • P波表示这个时期的开始
      • 等容收缩期isovolumetric contraction
        • 心室压力>心房压力，bicuspid valve关闭，有一个强劲的声音
        • 心室压力<动脉压力，体积不变化没有血液流出
        • QRS波表示这个时期的开端
      • 快速射血期rapid ejection
        • 心室压力>动脉压力，血液快速射出，心室体积下降
      • 减慢射血期reduced ejection
        • 心室压力<动脉压力，惯性导致射血继续但是减缓
        • 动脉压力由因血液流速降低而降低
        • T波表示这个时期的开端
      • 等容舒张期isovolumetric relaxation
        • 心室开始舒张
        • 心室压力<动脉压力，SL valve关闭，产生声音
        • 心室体积不变，因为所有valve都关闭(PA<Pv<Pao)
        • 存在一个Dicrotic notch(重搏切迹)，动脉压力变大
      • 快速充盈期rapid filling
        • 心室压力<心房压力，双尖瓣打开
        • 血液从肺静脉→左心房→左心室，充满2/3
        • 血液快速充满心室的湍流产生声音
      • 减慢充盈期reduced filling
        • 跟前面那个大差不差，慢一点
      • normal pressure-volume loop of the left ventricle
    • Cardiac function index
      • 每搏输出量stroke volume
        • the volume of blood ejected by a ventricle during each contraction.
        • 𝑉𝑠 = 𝑉𝑒𝑑 −𝑉𝑒𝑠 = 125−55 =70𝑚𝑙
        • Stroke Volume = End-Diastolic Volume - End-Systolic Volume
      • 射血分数ejection fraction
        • the fraction of the end diastolic volume that is ejected.
        • 𝑉s/𝑉𝑒𝑑 = 55~65%
      • 每分输出量cardiac output
        • the volume of blood ejected by a ventricle each minute. 𝑉s×𝐻𝑅 = 4.5~6.0𝐿/𝑚𝑖𝑛
        • 每搏输出量×心率
      • 心指数cardiac index
        • the cardiac output per square meter of body surface.
      • 每搏功stroke work
        • the amount of energy the ventricle converts to pump blood during each contraction.
        • The work performed by a ventricle converts into
          • ① potential energy that increases the blood pressure
          • ② kinetic energy of the blood flow (only 1%)
          • 𝑊 =𝑉𝑆×∆𝑃 + 1/2 ×𝑚𝑆×𝑣^2
          • 𝑊𝐿𝑉 = 6×𝑊𝑅𝑉 左心室每博功是右心室的6倍
    • Cardiac reserve
      • At rest, cardiac output = 56L，maximum cardiac output =2530L
      • Cardiac reserve (心力储备) is the difference between a person’s maximum cardiac output and cardiac output at rest.
      • includes
        • stroke volume reserve (搏出量储备)
          • Ved=125→140ml, Ves=55→20ml
        • heart rate reserve (心率储备)
          • 75→180 beats/min.
          • However, heart rate over 180 beats/min shortens the diastole too much, leading to insufficient ventricular filling and decreased cardiac output
      • 普通人的心力储备主要来源于心跳增加
    • Factors controlling cardiac output
      • 𝐶𝑎𝑟𝑑𝑖𝑎𝑐 𝑜𝑢𝑡𝑝𝑢𝑡 = V𝑠 × HR
      • Factors controlling V𝑠
        Vs = Ved - Ves
        • preload
          影响Ved
          • Preload = initial length = Ved → Ped = PA at atrial systole
            刚开始收缩时候心室心房血压相等
          • relaxed cardiac muscle is at less than optimum length
          • Additional stretch therefore produces a significant increase in contraction force
          • normal Ped = 5~6mmHg
          • optimum Ped = 12~15mmHg
          • When cardiac output is regulated by changes in cardiac muscle fiber length, it is referred to as heterometric regulation 异长自身调节
        • afterload
          影响Ves
          • Afterload is the resistance against which blood is expelled, namely the blood pressure in the aorta for the left ventricle
          • In theory, an increase in afterload causes stroke volume to decrease
          • In fact, increasing the arterial动脉的 pressure in the aorta does not decrease the cardiac output until the mean平均 arterial pressure rises above 160mmHg
        • contractility
          • Contractility is mainly determined by the numbers of activated cross-bridge and the enzyme activity of ATPase in myosin head
          • Given a constant preload, the stroke volume can be changed by neural/humoral regulation.
          • Effect on the strength of cardiac contraction is called inotropic action 变力作用
      • Factors controlling HR
        • Effect on the heart rate is called chronotropic action 变时作用
      • 图
      • 图2
  • Anatomy of the blood vessels
    • 三层血管
      • Tunica interna
        • Endothelium内皮细胞 is a layer of squamous epithelium.
        • It forms the tunica interna with a basement membrane, and is in direct contact with the blood
        • 图
      • Tunica media
        • The tunica media is a relatively thick layer comprising mainly smooth muscle and substantial大量的 amounts of elastic fibers
      • Tunica externa
        • The tunica externa is the outermost connective tissue layer, composed primarily of collagen fibers.
        • It contains numerous autonomic nerves自主神经, tiny blood vessels called vasa vasorum (血管滋养管) that supply large vessels
      • 图
    • 不同类型的血管
      • arteries
        • Large arteries
          elastic arteries， conducting arteries
          • have multiple sheets of elastic lamellae → elastic arteries
          • elastic lamellae separates multiple layers of vascular smooth muscle
          • Elastic arteries function as a pressure reservoir
          • They conduct blood from the heart to medium arteries → conducting arteries
        • Medium arteries
          muscular arteries，distributing arteries
          • have more smooth muscle and less elastic lamellae → muscular arteries
          • diatribute blood to different places → distributing arteries
        • Small arteries and arterioles 小动脉
          resistance arteries
          • Small arteries and arterioles are distinguished from one another by the number of smooth muscle cell layers in tunica media
          • Because of their diameters, small arteries and arterioles produce a large resistance against the blood flow → resistance arteries
      • Capillaries
        exchange vessels
        • 特点
          • 80,000 kilometers of capillaries
          • The endothelial cells form a tube just large enough to allow the passage of RBCs one at a time. In many capillaries, the lumen is so narrow that RBCs fold on themselves to pass through the vessel
          • primary function is exchange of substances between the blood and the interstitial fluid → exchange vessels
          • composed of only a single layer of endothelial cells and a basement membrane, lacking both a tunica media and a tunica externa
        • 分类
          根据物质穿过的难易程度分类
          • Continuous capillaries
            • The endothelial cells, held together by tight junctions, form a continuous tube.
            • Cells are separated by narrow intercellular clefts (4nm), which hold back blood cells, platelets and large molecules like plasma protein.
            • Continuous capillaries are found in the CNS中枢神经系统, the skin, lungs and muscles.
          • Fenestrated capillaries
            • The plasma membranes of endothelial cells in these capillaries have many fenestrations窗孔 (70-100nm)
            • Fenestrated capillaries are found in sites of active secretion, absorption or filtration, such as the endocrine glands内分泌腺, intestinal tract肠道, and kidney
          • Discontinuous capillaries
            • Discontinuous capillaries (sinusoidal capillaries窦状毛细血管/sinusoids) have large openings in their endothelial cells that are separated by wide irregular intercellular gaps.
            • Also, endothelial cells rest on a discontinuous basement membrane
            • Proteins and even blood cells can pass through these capillaries
            • These capillaries can be found in the liver肝脏, spleen脾脏 and red bone marrow红骨髓
      • Veins
        capacitance vessels
        • relatively thin-walled and flaccid松弛, and expand easily to accommodate an increased volume of blood → capacitance vessels
        • many contain venous valves that direct blood toward the heart

下半

  • Vascular physiology血管生理
    • Hemodynamics血流动力学
      • 血液分布
      • Blood flow 血流量
        • the volume of blood that passes a given site in the circulation in a given time
        • Poiseuille’s law
          • Q流量
          • r管道半径
          • η粘度系数
          • ΔP血管两侧压力差
          • L管道长度
        • laminar flow 层流
          • blood flows at a steady rate through a long, smooth blood vessel, it flows in streamlines
          • Poiseuille’s law can be applied to it
        • turbulent flow 湍流
          • blood flows in all directions and continually mixes within the vessel
          • Usually if Re>2000, turbulence will occur (v is velocity of blood flow, d is the vessel diameter, p is density, η is the viscosity)
        • Blood resistance
          • Blood resistance is the opposition to blood flow due to friction between blood and the walls of blood vessels
          • 𝑄 = ∆𝑃 / R
          • 𝑅= 8𝜂𝐿 / π𝑟4
          • R可以跟电路一样算串联并联
    • Arterial blood pressure动脉血压
      • Blood pressure is the force exerted by blood against a vessel wall
      • Systolic pressure 100120mmHg, diastolic pressure 6080mmHg
      • 动脉血压的形成
        • Sufficient blood filling in the circulatory system
        • Ejection of blood by the heart
        • Peripheral resistance
        • The elastic distention of the aorta and large arteries
      • 测量血压
        • direct measurements
        • indirect measurements
          • Korotkoff sound method
      • 血压的影响因素
        • Stroke volume每搏输出量↑, arterial blood↑, pressure on the vessel wall↑, systolic pressure↑
        • Heart rate↑, period of diastole↓, blood leaving the aorta during diastole↓, blood remaining in the aorta↑, diastolic pressure↑
        • Peripheral resistance外周阻力↑, blood velocity during diastole↓，blood remaining in the aorta↑, diastolic pressure↑
        • Arterial elasticity↓, blood pressure buffering↓, systolic pressure↑, diastolic pressure↓
        • Blood loss↓, blood pressure↓
    • Pressure pulse 脉搏
      • Pressure pulse is a periodic change of the pressure and volume of the blood vessel
      • 图像
        • The ascending limb - rapid ejection
        • The descending limb - reduced ejection & diastole
        • The dicrotic notch (降中峡) - blood backflows at the moment of closure of SL valves
      • Transmission of the pressure pulse is a bit faster than the blood flow
      • The greater compliance血管顺应性 of the each vascular segment, the slower the velocity
        顺应性是指血管在压力作用下扩张的能力
        • 3~5m/s in the aorta
        • 7~10m/s in large arteries
        • 15~35m/s in small arteries
    • Venous circulation
      • The pressure in the venules is 12~18mmHg, and 0mmHg in the right atrium (veins have little resistance)
      • Venous return is affected by
        • ①mean filling pressure (平均充盈压)
        • ②contractility of cardiac muscle
        • ③ gravity
        • ④skeletal muscle pump
        • ⑤thoracic pump 胸腔泵
    • Microcirculation
      • The arterioles小动脉, capillaries and venules小静脉 form the miscrocirculation
      • blood flows intermittently through capillaries due to vasomotion (血管运动), which may occur 5 to 10 times per minute
      • 血管运动是括约肌间歇性收缩舒张，控制血流
    • Capillary exchange
      • 四种方法
      • 判断水往哪流 +BP-HP-πB +血压-外面的水压-血液的渗透压(吸水)
  • Cardiovascular regulatory mechanisms
    • Neural regulation
      • afferent parts传入部分
        • Baroreceptors 压力感受器
          • detect blood pressure，High BP increases discharge rate of baroreceptors.
          • 上面的是颈动脉窦，下面的是主动脉弓
          • carotid sinus 颈动脉窦
            • carotid sinus 颈动脉窦 → carotid sinus nerve (Hering’s nerve) → glossopharyngeal nerve 舌咽神经 → cardiovascular center in the medulla oblongata 延髓
          • aortic arch 主动脉弓
            • aortic arch 主动脉弓 → depressor nerve (aortic nerve) → vagus nerve → cardiovascular center in the medulla oblongata 延髓
        • Chemoreceptors 化学感受器
          • detect O2, CO2 and H+in the blood
          • 除了出发的位置不同，神经与压力感受器相同
          • carotid bodies颈动脉体
            • carotid bodies颈动脉体 → carotid sinus nerve (Hering’s nerve) → glossopharyngeal nerve → cardiovascular center in the medulla oblongata 延髓
          • aortic bodies主动脉体
            • aortic bodies主动脉体 → depressor nerve (aortic nerve) → vagus nerve → cardiovascular center in the medulla oblongata 延髓
        • Cardiopulmonary receptors 心肺感受器
          • in the walls of atria, ventricles and pulmonary veins detect stretches and chemicals
          • Inputs from the receptors → vagus nerve → cardiovascular center
      • the center
        • The cardiovascular center is located in the medulla oblongata延髓 of brainstem脑干
        • The nucleus tractus solitaries (NTS, 孤束核) of medulla is a sensory area to receive signals from the vagus and glossopharyngeal nerves
        • vasoconstrictor(RVLM)，vasodialator(CVLM)，cardioinhibitor(nucleus ambiguus (疑核) and dorsal motor nucleus (背核)) 注意RVLM控制交感神经，可以控制心脏与血管，并不只是血管
        • 交感神经路径
        • 迷走(副交感)神经路径
        • 血压调控
          • controlled by the sympathetic nerves only
          • Receptors → NTS → CVLM -| RVLM→ sympathetic nerves
        • 心脏调控
          • controlled by the sympathetic and the vagus (parasympathetic) nerves
          • Receptors → NTS → CVLM -| RVLM→ sympathetic nerves
          • Receptors → NTS → nucleus ambiguus/dorsal motor nucleus → vagus nerves
          • 交感神经控制大部分，迷走神经主要控制心房
      • efferent parts
        • sympathetic nerves
          • The sympathetic nerves that innervate the heart start at T1~T5
          • When excited, these nerves release norepinephrine (NE, 去甲肾上腺素)
          • NE 作用在β1-adrenoceptors of cardiac muscles与α1-adrenoceptors of vascular smooth muscles，看得出最后一个产生了PKA，一个产生了PKC
          • Cardiac effects
            • PKA phosphorylates ICa-L, ICa-T, If channels, and dissociate Ca2+ pump
            • Working cells → ICa-L↑, Ca2+ pump↓, [Ca2+]i↑, contraction↑, positive inotropy (正性变力)
            • Autorhythmic cells → If↑, ICa-T↑, ICa-L↑, spontaneous depolarization↑, heart rate↑, positive chronotropy (正性变时)
          • Vascular effects
            • [Ca2+]i↑, calmodulin activity↑, vasoconstriction↑, vessel diameter↓, vascular resistance↑, blood pressure↑
        • vagus nerves
          • The vagus nerves start at the medulla
          • When excited, the vagus nerves that innervate the atria release acetylcholine乙酰胆碱
          • Ach acts on the muscarinic (毒蕈碱型) receptors M2, inhibits the adenylate cyclase and reduce [cAMP]i
          • Cardiac effects
            • Phosphorylation of ICa-L, ICa-T, If channels weaken due to reduced PKA activity by [cAMP]i↓; IK-Ach is activated
            • Working cells → ICa-L↓, [Ca2+]i↓, IK-Ach↑, repolarization↑, contraction↓, negative inotropy (负性变力)
            • Autorhythmic cells → If↓, ICa-T↓, ICa-L↓, spontaneous depolarization↓, heart rate↓, negative chronotropy (负性变时)
      • the reflex
    • Humoral regulation
      • Epinephrine & norepinephrine 肾上腺素&去甲肾上腺素
        • 被神经分泌就是神经递质，被肾上腺分泌就是激素
        • adrenal medulla (肾上腺髓质)合成出来的80%是肾上腺素，20%是去甲肾上腺素
        • 不同受体
          • α1
            • in the vascular smooth muscle of skin, kidney and digestive tract
            • vasoconstriction
          • α2
            • in the neurons
          • β1
            • in the cardiac muscle
            • positive intropic and chronotropic effects
          • β2
            • in the skeletal muscle, and the smooth muscle of hepatic肝 vessels and respiratory tract 呼吸道
            • vasodilation
      • Renin-angiotensin system 肾素-血管紧张素系统
        • Vasoconstriction
        • 机理
        • 肾素是一种酶，可以水解angiotensinogen
        • AngⅠ functions solely as the precursor of AngⅡ
        • Angiotensin-converting enzyme (ACE) exists in the pulmonary vascular endothelium
        • AngⅡ binds to AT1 receptors that activate Gq and Gi 最强大的收缩剂
      • Vasopressin 血管加压素
        • VP is secreted by hypothalamus下丘脑
        • It binds to V1 receptors of vascular smooth muscle
      • Atrial natriuretic peptide 心房钠尿肽
        • ANP is secreted by stretched atrial muscles
        • ANP can strengthen Ca2+ pump and inhibit PLC
        • vasodilation
      • NO
        • 可以使cGMP↑，Ca2+↓
        • vasodilation
    • Neurohumoral regulation
      • The neurohumoral regulation of cardiovascular system is a negative feedback control
      • Changes of cardiovascular functions are eventually reflected by blood pressure
    • Autoregulation
      • Heterometric regulation
        • 肌肉长度自动调节力度
      • Metabolites
        • for example, lactate and adenosine stimulate vasodilation
  • Circulation through special regions
    • Coronary circulation
      • coronary冠状动脉连着主动脉刚出去的一部分
      • diagram of the epicardial, intramuscular and subendocardial coronary vasculature 心外膜、心肌内和心内膜下冠状动脉血管分布的示意图
      • phasic flow of blood through the coronary capillaries，血流量变化大，因为靠近心室
    • Pulmonary circulation 肺循环
      • Low resistance
      • low blood pressure
      • low capacity
    • Cerebral circulation 脑循环
      • High blood flow and little change.
      • Blood-brain barrier