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Cardiovascular Physiology

Cardiovascular Physiology. 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. Vascular Physiology (血管生理学). Lecture Outline. Functional parts of blood vessels Hemodynamics

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Cardiovascular Physiology

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  1. Cardiovascular Physiology 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

  2. Vascular Physiology(血管生理学)

  3. Lecture Outline • Functional parts of blood vessels • Hemodynamics • Arterial blood pressure • Microcirculation • Venous pressure and venous return • The lymphatic system

  4. Functional parts of blood vessels • Elastic vessels (Windkessel vessels) • (弹性血管) • Resistance vessels (Precapillary resistance vessels)(阻力血管) • Exchange vessels(交换血管) • Capacitance vessels(容量血管) • Distribution vessels(分布血管) • Shunt vessels(短路血管)

  5. Hemodynamics(血流动力学) • Blood flow Q= DP/R = (P1-P2)/R

  6. Q: cardiac output, 5 L/min R: total peripheral resistance PA: aortic pressure Q= PA/R

  7. Resistance of blood flow Poiseuille Law: Q=pDPr4/8hL h: viscosity r: radius of the vessel L: length of the vessel R= 8hL/pr4 Q= DP/R Jean Louis Marie Poiseuille \pwä-'zəi\ (April 22, 1799 - December 26, 1869) was a French physician and physiologist. Poiseuille was born in Paris, France. From 1815 to 1816 he studied at the École Polytechnique in Paris. He was trained in physics and mathematics. In 1828 he earned his D.Sc. degree with a dissertation entitled Recherches sur la force du coeur aortique. He was interested in the flow of human blood in narrow tubes.

  8. r: main determinant of blood flow

  9. Arterial blood pressure(动脉血压) Arteries

  10. Blood pressure measurement1. Direct (invasive) measurement technique

  11. 2. Indirect (non-invasive) measurement technique

  12. Systolic pressure (SP,收缩压): the maximum arterial pressure reached during peak ventricular ejection Diastolic pressure (DP,舒张压): the minimum arterial pressure just before ventricular ejection begins Pulse pressure (PP,脉压): the difference between SP and DP Mean arterial pressure (MAP,平均动脉压): the average pressure in the cardiac cycle (=DP+1/3PP)

  13. Mean arterial pressure (MAP)

  14. To estimate systolic and diastolic pressures, pressure is released from an inflatable cuff on the upper arm while listening as blood flow returns to the lower arm.

  15. Click here to play the Sphygmomanometry Flash Animation

  16. Classification of blood pressure for adults age 18 years and older The classification chart is based on adults, aged 18 and older, who are not taking high blood pressure medicines and who are not acutely ill. If systolic and diastolic measurements fall into different categories, the higher category should be used to classify the person's blood pressure status.

  17. Factors affecting arterial blood pressure • Stroke volume • Heart rate • Peripheral resistance • Elastic vessels • Blood volume Ventricular ejection

  18. Q: cardiac output (CO) R: total peripheral resistance (SVR) PA: aortic pressure (MAP) Q= PA/R MAP = CO  SVR

  19. 3 2 1 4 5

  20. The blood moved in a single heart contraction stretches out the arteries, so that their recoil continues to push on the blood, keeping it moving during diastole. Movement of blood into and out of the arteries during the cardiac cycle

  21. Arterial pulse(动脉脉搏)

  22. In response to the pulsatile contraction of the heart: pulses of pressure move throughout the vasculature, decreasing in amplitude with distance

  23. Arterial pulse recorded in different vessels

  24. Arterial pulse recorded under different conditions

  25. Microcirculation(微循环) Function: Transfer of substances between blood & the tissues

  26. Structure of microcirculation A-V shunt

  27. 2 1 3 A-V shunt 4 5 3 pathways • Circuitous channel (Nutritional channel)(营养通路)

  28. 2 1 3 A-V shunt 4 5 • Thoroughfare channel(直捷通路)

  29. 2 1 3 A-V shunt 4 5 • Arteriovenous shunt (A-V shunt)(动-静脉短路)

  30. Blood travels from artery to arteriole to capillary to venule to vein

  31. Arterioles(微动脉) • Two major roles: • To be responsible for determining the relative blood flow in individual organs at any given MAP • To be a major factor in determining MAP

  32. Dynamic adjustments in the blood distribution to the organs is accomplished by relaxation and contraction of circular smooth muscle in the arterioles.

  33. Click here to play the Arteriolar Radius & Blood Flow Flash Animation

  34. Click here to play the Arteriolar Resistance & BP Flash Animation

  35. Local Control of Blood Flow • The mechanism independent of nerves or hormones by which organs and tissues alter their own arteriolar resistances, thereby self-regulating their blood flows • Active hyperemia(主动充血) • Flow autoregulation(血流自身调节) • Reactive hyperemia(反应性充血) • Local response to injury(对损伤的局部反应)

  36. Local control of organ blood flow Active hyperemia and flow autoregulation differ in their cause but both result in the production of the same local signals that provoke vasodilation.

  37. Reactive hyperemia – When an organ or tissue has had its blood supply completely occluded, a profound transient increase in its blood flow occurs as soon as the occlusion is released

  38. Response to injury – Tissue injury causes a variety of substances to be released locally from cells or generated from plasma precursors. These substances make arteriolar smooth muscle relax and cause vasodilation in an injured area

  39. Extrinsic Control • Sympathetic nerves(交感神经) • Parasympathetic nerves(副交感神经) • Noncholinergic, nonradrenergic autonomic neurons (NO or other noncholinergic vasodilator substances)(NANC) • Hormones (epinephrine, angiotensin II, vasopressin, atrial natriuretic peptide)

  40. Sympathetic stimulation of alpha-adrenergic receptors cause vasoconstriction to decrease blood flow to that location. Sympathetic stimulation of beta-adrenergic receptors lead to vasodilation to cause an increase in blood flow to that location.

  41. Renin-angiotensin system(肾素-血管紧张素系统)

  42. ANGII can be produced directly by conversion of angiotensinogen by the tissue plasminogen activator (tPA), cathepsin G and tonin or by hydrolysis of angiotensin I by chymase and cathepsin G. CAGE = chymostatin-sensitive angiotensin II-generating enzyme

  43. Robert Toto & Biff F. Palmer. Am J Nephrol 2008;28:372–380

  44. Vasopressin(血管升压素)

  45. Endothelium-derived vasoactive substances • Vasodilator factors • PGI2 – prostacyclin(前列环素) • EDRF (endothelium-derived relaxing factor, nitric oxide) • EDHF (endothelium-dependent hyperpolarizing factor)

  46. The 1998 Nobel Prize in Physiology or Medicine Nitric oxide as a signaling molecule in the cardiovascular system Louis J Ignarro Ferid Murad Robert F Furchgott

  47. Sildenafil, the prototypical PDE5 inhibitor A phosphodiesterase type 5 inhibitor, often shortened to PDE5 inhibitor, is a drug used to block the degradative action of phosphodiesterase type 5 on cyclic GMP in the smooth muscle cells lining the blood vessels supplying the corpus cavernosum of the penis. These drugs are used in the treatment of erectile dysfunction, and were the first effective oral treatment available for the condition. Because PDE5 is also present in the arterial wall smooth muscle within the lungs, PDE5 inhibitors have also been explored for the treatment of pulmonary hypertension, a disease in which blood vessels in the lungs become abnormally narrow.

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