Special Circulation Qiang XIA (夏强), MD & PhD Department of Physiology Room C518, Block C, Research Building, School of Medicine Tel: 88208252 Email: xiaqiang@zju.edu.cn

System Overview The blood flow to organs depends on ⒈ The difference between aortic pressure and central venous pressure ⒉ The diastolic and systolic state of blood vessel in this organ The blood flow to individual organs must vary to meet the needs of the particular organ, as well as of the whole body

System Overview Neural, myogenic, metabolic, and endothelial mechanisms control regional blood flow Neural mechanism: Autonomic nervous system (sympathetic division) Myogenic mechanism: Metabolic mechanism: PO2, pH, etc. Endothelial mechanism: NO, EDHF, PGI2, ET, EDCF, etc. Blood pressure Cardiac output Local blood flow Autoregulation in the vessels of heart, brain, skeletal muscle, and kidneys Local control in the vessels of heart, brain, skeletal muscle during exercise Relaxing or contracting VSMCs

Sophisticated feedback, System Overview Sophisticated feedback, Mechanical forces, etc. Neural mechanism: Autonomic nervous system (sympathetic division) Myogenic mechanism: Metabolic mechanism: PO2, pH, etc. Endothelial mechanism: NO, EDHF, PGI2, ET, EDCF, etc. Local circulation Resting vasomotor tone Vasomotor control Electrical and chemical signalling VSMCs ECs Gap junction

System Overview I. Coronary Circulation 冠脉循环 II. Cerebral Circulation 脑循环

Coronary circulation Heart: view from front

Coronary circulation Heart: view from diaphragm

—— Provides blood flow to the heart Coronary circulation —— Provides blood flow to the heart 1. Heart muscle consumes as much O2 as does equal mass of SM during vigorous exercise 2. Heart tissue extracts maximal amount of O2 during rest 3. he only way to increase of energy is by increasing blood flow 左冠状动脉 右冠状动脉 供血区域 左心室前部 左心室后部 和左侧部 和右心室 回流途径 冠状窦→右心房 心前静脉→右心房

1. 冠脉循环的解剖特点 Diagram of the epicardial, intramuscular, and subendocardial coronary vasculature

1. 冠脉循环的解剖特点 ① The branches of left and right coronary artery often penetrate myocardium in direction perpendicular to cardiac surface ② Myocardial capillary distribution is extremely abundance ③ Collateral coincidence between coronary is less

2. 冠脉循环的生理特点 ① The pathway is short and blood flow is fast ② Blood pressure is high ③ Blood flow is big and it is 4%～5% of cardiac output ④ Arteriovenous oxygen difference is great during resting period

2. 冠脉循环的生理特点 ⑤ Blood flow fluctuates with cardiac cycle Isovolumic contraction phase ↓↓→ rapid ejection phase ↑→reduced ejection phase ↓→ diastolic phase ↑ (isovolumic relaxation phase↑↑)

2. 冠脉循环的生理特点 动脉舒张压高低和舒张期长短是决定冠脉血流量的重要因素 收缩及舒张对右心室的影响不及对左心室明显

3. 冠脉血流量的调节 Blood flow Resting: 60-80 ml/100g/min Exercise: 300-400 ml/100g/min O2 consumption 7-9 ml/100g/min is about 65-70% of O2 extraction

3. 冠脉血流量的调节 （1）心肌代谢水平的影响 心肌活动增强→ 耗氧量增加→局部PO2 ↓ →腺苷↑→小动脉口径↑→血流量↑ 心肌收缩的能量来源几乎仅依靠有氧代谢 心肌耗氧量大，摄氧多，摄氧潜力低，对氧需求增加主要依赖冠脉扩张 心肌活动增强→ 耗氧量增加→局部PO2 ↓ →腺苷↑→小动脉口径↑→血流量↑ 其次，乳酸、H+、CO2、缓激肽、前列腺素E等也有一定的扩血管作用

3. 冠脉血流量的调节 （2）神经调节 交感神经的直接收缩作用＜继发性舒张作用 交感神经+→NE →冠脉a受体→冠脉收缩 ↓ 冠脉受迷走及交感神经支配 整体安静时，神经因素对冠脉的舒缩影响不大 交感神经+→NE →冠脉a受体→冠脉收缩 ↓ 心肌b1受体→心肌正变时正变力正变传导↑→耗氧量↑ →代谢产物↑ →冠脉舒张 交感神经的直接收缩作用＜继发性舒张作用

3. 冠脉血流量的调节 （2）神经调节 迷走神经的直接舒张作用＜继发性收缩作用 迷走神经+→ ACh →冠脉M受体→冠脉舒张 ↓ 心肌M受体 心肌负变时负变力负变传导↑→ 耗氧量↓→代谢产物↓ →冠脉收缩 迷走神经的直接舒张作用＜继发性收缩作用

3. 冠脉血流量的调节 （3）激素调节 NE, Adr → a受体和b受体 → 冠脉收缩或舒张 T4 → 代谢↑ → 血流量↑ VP，ANGⅡ → 血管收缩 → 血流量↓ Adrenomedullin 肾上腺髓质素（ADM)：1993年，Kitamura分离出的一种新的生物活性肽；ADM对大动脉、冠状动脉、周围阻力血管均有明显的扩张作用

Coronary heart disease Coronary heart disease results from coronary atherosclerosis, which leads to cardiac ischemia and anoxia—— ischemic heart disease Etiology The atherosclerotic plaque broken through the endothelium → blood platelets begin to adhere to → fibrin begins to be deposited → red blood cells entrapped → a blood clot → a local thrombus → occlude the vessel 本病的发生与冠状动脉粥样硬化狭窄的程度和支数有密切关系 好发部位：前降支上、中1/3，右冠状动脉中1/3

Collateral vessel growth can provide blood flow to ischemic regions Vasodilator drugs may comprise myocardial flow through “coronary steal”

Cerebral circulation The major arteries of the brain. (A) Ventral view, Lateral (B) and (C) midsagittal views, (D) Idealized frontal section circle of Willis

Cerebral circulation Blood supply of the three subdivisions of the brainstem. (A) Diagram of major supply. (B) Sections through different levels of the brainstem indicating the territory supplied by each of the major brainstem arteries

Cerebral circulation Cerebral circulation —— Provides blood flow to the brain 大脑半球前2/3脑区：颈内动脉 大脑半球的后1/3脑区，小脑，脑干：椎动脉

Cerebral circulation 1. 脑循环特点 ① 血流量大，耗氧量高 ② 血管舒缩受限，血流量稳定，变动范围小 ③ 局部化学环境（PCO2、PO2）对脑血管舒缩活动影响大 ④ 神经因素对脑血管活动的调节作用小 ⑤ 存在血脑屏障和血脑脊液屏障

Cerebral circulation 1. 脑循环特点 Changes in regional blood flow SENS 1: Low-intensity electrical stimulation of hand SENS 2:High-intensity electrical stimulation of hand

Cerebral circulation 2. 脑血流调节 （1）脑血管的自身调节 脑的血流量主要取决于脑的动脉和静脉的压力差和脑血管的血流阻力 影响脑血流量的主要因素是颈动脉压 动脉BP （MAP=60–140 mmHg）↑→血流速度↑→血流量↑

Cerebral circulation 2. 脑血流调节 ↓ ↓ ↓ （2）PCO2与PO2对脑血流的影响 缺氧 乳酸，丙酮酸，酸性代谢产物↑ ↓ ↓ PCO2 ↑或PO2 ↓→ H2CO3 → [H+]↑→ 脑血管舒张→ 脑血流量增多→ [H+]↓→ 恢复内环境稳态 ↓ 氧供应↑

Cerebral circulation 2. 脑血流调节 （3）脑的代谢对脑血流的影响 （4）神经调节对脑血流的影响 脑代谢活动↑→ 代谢产物如H+↑、K+↑、腺苷↑、PO2↓→ 脑血管舒张 （4）神经调节对脑血流的影响 神经调节在脑血管活动调节中所起的作用很小 激烈运动时，交感神经兴奋，血压显著升高，脑大动脉和中动脉收缩，防止高压传递至脑部小血管致使脑出血

Cerebral circulation 3. 血-脑脊液屏障和血-脑屏障 脑屏障的结构与位置关系 血-脑屏障； 血-脑脊液屏障； 脑脊液-脑屏障； AS. 星形胶质细胞； N. 神经元； CSF. 脑脊液 脑屏障生理功能：保持脑组织周围稳定的化学环境和防止血液中有害物质侵入脑内，阻止某些激素进入脑内干扰神经元的正常活动。

Cerebral circulation 3. 血-脑脊液屏障和血-脑屏障 （1）血-脑脊液屏障（BBB） 血液和脑脊液之间的一种特殊屏障，称为血-脑脊液屏障 结构基础： 毛细血管内皮之间存在紧密连接； 毛细血管壁和脉络丛细胞中转运各种物质的特殊载体系统 易通透：H2O，O2，CO2，大多数脂溶性物质 较难通透：Na+，K+，Cl– ，蛋白质，非脂溶性大分子有机物质

Cerebral circulation 3. 血-脑脊液屏障和血-脑屏障 （2）血-脑屏障 血液和脑组织之间也存在类似的屏障，限制物质在血液和脑组织之间的自由交换——血-脑屏障 结构基础 毛细血管内皮、基膜和星状胶质细胞的血管周足等结构 易通透：脂溶性物质——O2，CO2，某些麻醉药，乙醇 水溶性物质 —— 葡萄糖，氨基酸 较难通透：甘露醇，蔗糖

The End.