生理學(xué)雙語-呼吸-2課件

1、第二節(jié) 呼吸氣體的交換一、氣體交換原理（一）氣體的擴散機體內(nèi)的氣體交換就是以擴散方式進行的。氣體擴散速率受下列因素的影響：11氣體的分壓差 在混合氣體中，每種氣體分子運動所產(chǎn)生的壓力為各該氣體的分壓，它不受其它氣體存在的影響，只決定于它自身的濃度。兩個區(qū)域之間的分壓差（P）是氣體擴散的動力，分壓差大，擴散快。22. 氣體的分子量和溶解度 擴散速率和該氣體分子量（MW）的平方根成反比，與溶解度成正比。33擴散面積和距離氣體擴散速率與擴散面積（A）成正比。與擴散距離(d)成反比。4溫度 擴散速率與溫度（T）成正比。4in which D is the diffusion rate, P is th

2、e pressure difference between the two ends of the diffusion pathway, A is the cross-sectional area of the pathway, S is the solubility of the gas, d is the distance of diffusion, and MW is the molecular weight of the gas.5(4) the molecular weight of the gas, and (5) the temperature of the fluid. In

3、the body, the last of these factors, the temperature, remains reasonably constant and usually need not be considered.7A.IntroductionGases can move from one point to another by diffusion and that the cause of this movement is always a pressure difference from the first point to the next. Thus, oxygen

4、 diffuses from the alveoli into the pulmonary capillary blood because the oxygen pressure (PO2) in the alveoli is greater than the PO2 in the pulmonary blood. 8Similarly, it diffuses out of the blood into the alveoli because the PCO2 in the pulmonary capillary blood is greater than that in the alveo

5、li.Basically, then, the transport of oxygen and carbon dioxide by the blood depends on both diffusion and the movement of blood. 10呼吸膜含表面活性物質(zhì)的液體層肺泡上皮細胞層肺泡上皮細胞基膜層 間隙毛細血管基膜層毛細血管內(nèi)皮細胞層三、肺換氣1112 V/Q ratiois the ratio of alveolar ventilation (V) to pulmonary blood flow (Q). Matching ventilation and perfus

6、ion is important to achieve the ideal exchange of O2and CO2.If the frequency, tidal volume, and cardiac output are normal, the V/Q ratio is approximately 0.8. This situation results in an arterial PO2 of 100 mm Hg and an arterial PCO2 of 40 mm Hg.14如果VA/Q比值增大，這就意味著通氣過剩，血流不足，部分肺泡氣未能與血液氣充分交換，致使肺泡無效腔增大

7、。15肺泡無效腔增大動靜脈短路171. V/Q ratio in airway obstructionIf the airways are completely blocked (e.g., by a piece of steak caught in the trachea), then ventilation is zero. If blood flow is normal, then V/Q is zero.18There is no gas exchange in a lung that is perfused but not ventilated. The PO2 and PCO2 o

8、f pulmonary capillary blood (and, therefore, of systemic arterial blood) will approach their values in mixed venous blood.192. V/Q ratio in blood flow obstructionIf blood flow to a lung is completely blocked (e.g., by an embolism occluding a pulmonary artery), then blood flow to that lung is zero. I

9、f ventilation is normal, then V/Q is infinite.There is no gas exchange in a lung that is ventilated but not perfused. 20動脈靜脈O2(30mmHg)CO2(50mmHg)O2(100mmHg)CO2(40mmHg)O2(40mmHg)CO2(46mmHg)組織細胞三、組織換氣21Diffusion of Oxygen from the Peripheral Capillaries into the Tissue FluidWhen the arterial blood rea

10、ches the peripheral tissues, its PO2 in the capillaries is still 95 mm Hg. Yet the PO2 in the interstitial fluid that surrounds the tissue cells averages only 40 mm Hg. 22When oxygen is used by the cells, most of it becomes carbon dioxide, and this increases the intracellular PCO2 Because of the hig

11、h tissue cell PCO2, carbon dioxide diffuses from the cells into the tissue capillaries and is then carried by the blood to the lungs. In the lungs, it diffuses from the pulmonary capillaries into the alveoli. Thus, at each point in the gas transport chain, carbon dioxide diffuses in a direction exac

12、tly opposite that of the diffusion of oxygen. 24Yet there is one major difference between the diffusion of carbon dioxide and that of oxygen: carbon dioxide can diffuse about 20 times as rapidly as oxygen. Therefore, the pressure differences required to cause carbon dioxide diffusion are, in each in

13、stance, far less than the pressure differences required.25一、氧和二氧化碳在血液中運輸?shù)幕拘问剑ㄒ唬┪锢砣芙?比例?。ǘ┗瘜W(xué)結(jié)合 主要O2溶解的O2化學(xué)結(jié)合的O2溶解的O2O2CO2溶解的CO2化學(xué)結(jié)合的CO2溶解的CO2 CO227二、氧的運輸（一）物理溶解占血液總氧含量的約1.5%（二）化學(xué)結(jié)合占血液總氧含量的約98.5%與血紅蛋白（Hb）進行化學(xué)結(jié)合28Transport Of Oxygen In The BloodNormally, about 97 per cent of the oxygen transported fr

14、om the lungs to the tissues is carried in chemical combination with hemoglobin in the red blood cells. The remaining 3 per cent is transported in the dissolved state in the water of the plasma and cells. Thus, under normal conditions, oxygen is carried to the tissues almost entirely by hemoglobin.29

15、1. Hb的分子結(jié)構(gòu)1個珠蛋白4個血紅素四條多肽鏈 22每個血紅素有4個吡咯環(huán)，其中心有一個Fe2+一條多肽鏈和一個血紅素相連形成單體（亞單位）。30312. Hb與O2的結(jié)合特點（1）反應(yīng)快，可逆，不需要酶的催化，受O2分壓的影響。32（2）Fe2+與O2的結(jié)合是氧合，不是氧化。（3）1分子的Hb可以結(jié)合4分子的O2。33Reversible Combination of Oxygen with HemoglobinThe oxygen molecule combines loosely and reversibly with the heme portion of the hemoglob

16、in. When PO2 is high, as in the pulmonary capillaries, oxygen binds with the hemoglobin, but when PO2 is low, as in the tissue capillaries, oxygen is released from the hemoglobin. This is the basis for almost all oxygen transport from the lungs to the tissues.34 A. HemoglobinCharacteristicsglobular

17、protein of four subunitsEach subunit contains a heme, which is iron-containing porphyrin. 卟啉The iron is in the ferrous state (Fe2+), which binds O2, If iron is in the ferric state (Fe3+), it is methemoglobin高鐵血紅蛋白, which does not bind O235Each subunit has a polypeptide chain. Two of the subunits hav

18、e chains and two of the subunits have chains; thus, normal adult hemoglobin is called 22.36 O2 capacityis the maximum amount of O2 that can be bound to hemoglobin.O2 capacity is determined by the hemoglobin concentration in blood.37O2 capacity limits the amount of O2 that can be carried in blood.O2

19、capacity is measured at 100% saturation.38O2 content O2 content is the total amount of O2 carried in blood, including bound and dissolved O2,depends on the hemoglobin concentration and the Po2. 39Saturation of the hemoglobin.the percentage of hemoglobin bound with oxygen is called the percent satura

20、tion of the hemoglobin.40100ml血液中，Hb所能結(jié)合的最大O2量稱為氧容量。而實際結(jié)合的O2量稱為氧含量。氧含量和氧容量的百分比為氧飽和度。41 HbO2呈鮮紅色，去氧Hb呈紫藍色。當(dāng)表淺毛細血管血液中去氧Hb含量達5g/100ml血液以上時，皮膚、粘膜呈淺藍色，稱紫紺。423、氧離曲線（oxygen dissociation curve）是表示PO2與氧飽和度關(guān)系的曲線。呈S形。43上段：PO2 10060mmHg中段： PO2 6040mmHg下段： PO2 4015mmHg44上段 PO2 10060mmHg：曲線平坦，受O2分壓影響小。是Hb與O2的結(jié)合階段

21、。意義：當(dāng)外環(huán)境或吸入氣中的O2分壓下降，造成血PO2降低時，仍能為機體攝取和攜帶足夠的O2。45中段： PO2 6040mmHg曲線較陡，是HbO2釋放O2的部分。意義：當(dāng)動脈血流經(jīng)組織時，可釋放出適量的O2 ，滿足機體安靜狀態(tài)下對O2 的需求。46下段：PO2 4015mmHg曲線很陡，表明當(dāng)O2分壓稍有下降時，血氧飽和度將明顯降低。也是Hb與O2的解離階段。意義：當(dāng)動脈血流經(jīng)活動增強的組織時，可釋放足夠的O2 ，滿足活動增強組織對O2需求。471. Hemoglobin combines rapidly and reversibly with O2 to form oxyhemoglob

22、in.2. The hemoglobin- O2 dissociation curve is a plot of saturation of hemoglobin as a function 函數(shù)of PO2.a. At a PO2 of 100 mm Hg (e.g., arterial blood) hemoglobin is almost 100% saturated; O2 is bound to all four heme groups on all hemoglobin molecules.48The PO2 at 50% saturation is the P50. Fifty

23、percent saturation means that, on average, two of the four heme groups of each hemoglobin molecule have O2 bound.49The sigmoid shape of the curve is the result of a change in the affinity of hemoglobin as each successive O2 molecule binds to a heme site (called positive cooperativity).Binding of the

24、 first O2 molecule increases the affinity for the second O2 molecule, and so forth.50The affinity for the fourth O2 molecule is the highest.This change in affinity facilitates the loading of O2 in the lungs (flat portion of the curve) and the unloading of O2 at the tissues (steep portion of the curv

25、e).51 In the lungsAlveolar gas has a PO2 of 100 mmHg.Pulmonary capillary blood is arterialized by the diffusion of O2 from alveolar gas into blood, so that the PO2 of pulmonary capillary blood also becomes 100 mm Hg.52The curve is almost flat when the PO2 is between 60 mm Hg and 100 mm Hg. Thus, hum

26、ans can tolerate changes in atmospheric pressure (and PO2) without compromise of the O2-carryjng capacity of hemoglobin.53In the peripheral tissuesO2 diffuses from arterial blood to the cells.The gradient for O2 diffusion is maintained because the cells consume O2 for aerobic metabolism, keeping the

27、 tissue PO2 low.The lower affinity- of hemoglobin for O2 in this steep portion of the curve facilitates the unloading of O2 to the tissues.544、影響氧離曲線的因素通常用P50表示Hb對O2的親和力。P50是使Hb氧飽和度達50%時的PO2。P50增大，表明Hb對O2的親和力降低，曲線右移；P50降低，說明Hb對O2的親和力增加，曲線左移。5556（1）PCO2和pH的影響pH降低或PCO2升高，P50增大，曲線右移，促使O2的釋放；反之相反。影響因素：5

28、758波爾效應(yīng)（Bohr effect)：當(dāng)酸度增大時，Hb 對氧的親和力下降。當(dāng)酸度減小時相反。59生理意義可促進肺毛細血管血液的氧合（因為CO2從血進入肺泡，酸度下降）。又有利于組織毛細血管血液氧氣的釋放（因為CO2從組織入血，酸度上升）。60（2）溫度的影響 溫度升高，氧離曲線右移，促使O2的釋放；溫度降低，曲線左移，不利于O2釋放。61626364（3）2、3-二磷酸甘油酸 （2、3-DPG)2,3-DPG濃度升高，氧離曲線右移：2,3-DPG濃度升降低，曲線左移。65A number of factors can displace the dissociation curve in

29、one direction or the other in the manner shown in Figure below. This figure shows that when the blood becomes slightly acidic, with the pH decreasing from the normal value of 7.4 to 7.2, the oxygen-hemoglobin dissociation curve shifts, on average, about 15 per cent to the right. 66Conversely, an inc

30、rease in the pH from the normal 7.4 to 7.6 shifts the curve a similar amount to the left.67all of which shift the curve to the right, are (1) increased carbon dioxide concentration, (2) increased blood temperature, and (3) increased 2,3-diphosphoglycerate (DPG), a metabolically important phosphate c

31、ompound present in the blood but in different concentrations under different metabolic conditions.68The Bohr Effect: Increases in PCO2 or hydrogen ions (decreases in pH) shift the curve to the right, decreasing the affinity of hemoglobin for O2 and Increasing Delivery of Oxygen to the Tissues O2).69

32、For example, during exercise, the tissues produce more CO2, which decreases tissue pH and, through the Bohr effect, stimulates O2 delivery to the exercising muscle.70三、二氧化碳的運輸（一）物理溶解 每100ml靜脈血，物理溶解的CO2約占總量的的5% 。71（二） 化學(xué)結(jié)合碳酸氫鹽氨基甲酸血紅蛋白88%7%72Transport of carbon dioxide by the blood is not nearly so gr

33、eat a problem as transport of oxygen, because even in the most abnormal conditions, carbon dioxide can usually be transported in far greater quantities than can oxygen. 73However, the amount of carbon dioxide in the blood does have much to do with acid-base balance of the body fluids.741.Transport o

34、f Carbon Dioxide in the Dissolved StateTo begin the process of carbon dioxide transport, carbon dioxide diffuses out of the tissue cells in the dissolved molecular carbon dioxide form. A small portion of the carbon dioxide is transported in the dissolved state to the lungs, only about 0.3 milliliter

35、 of carbon dioxide is transported in the form of dissolved carbon dioxide by each 100 milliliters of blood. This is only about 7 per cent of all the carbon dioxide normally transported.75 碳酸氫鹽紅細胞內(nèi) 碳酸氫鉀血漿內(nèi) 碳酸氫鈉76Transport of Carbon Dioxide in the Form of Bicarbonate Ion The dissolved carbon dioxide i

36、n the blood reacts with water to form carbonic acid. Inside the red blood carbonic anhydrase碳酸酐酶 catalyzes the reaction between carbon dioxide and water, then the carbonic acid formed in the red cells (H2CO3) dissociates into hydrogen and bicarbonate ions (H+ and HCO3-). 77Most of the hydrogen ions

37、then combine with the hemoglobin in the red blood cells. In turn, many of the bicarbonate ions diffuse from the red cells into the plasma while chloride ions diffuse into the red cells to take their place (the chloride shift).78The reversible combination of carbon dioxide with water in the red blood

38、 cells under the influence of carbonic anhydrase accounts for about 70 per cent of the carbon dioxide transported from the tissues to the lungs. Thus, this means of transporting carbon dioxide is by far the most important of all the methods for transport. 792、HbNHCOOHHbNH2O2+H+CO2 HbNHCOOH+O2肺組織80Tr

39、ansport of Carbon Dioxide in Combination with Hemoglobin and Plasma Proteins-Carbaminohemoglobin. In addition to reacting with water, carbon dioxide reacts directly with amine radicals of the hemoglobin molecule to form the compound carbaminohemoglobin氨基甲酰血紅蛋白 (CO2Hgb). 81This combination of carbon

40、dioxide with the hemoglobin is a reversible reaction that occurs with a loose bond, so that the carbon dioxide is easily released into the alveoli, where the PCO2 is lower than in the tissue capillaries.82This carbaminohemoglobin mechanism provides transport of about 20 per cent of the total quantit

41、y of carbon dioxide.83（三）CO2的解離曲線（carbon dioxide dissociation curve）表示血液中CO2含量與PCO2關(guān)系的曲線，幾乎呈線形關(guān)系。8485The curve BELOW depicts this dependence of total blood carbon dioxide in all its forms on PCO2; this curve is called the carbon dioxide dissociation curve.86（四）Hb的結(jié)合對CO2運輸?shù)挠绊慜2與Hb結(jié)合將促使CO2釋放，這一效應(yīng)稱為 何爾

42、登效應(yīng)（Haldane effect)87The Haldane Effect :When Oxygen Binds with Hemoglobin, Carbon Dioxide is Released to Increase CO2 Transport88Earlier in the chapter, it was pointed out that an increase in carbon dioxide in the blood causes oxygen to be displaced from the hemoglobin (the Bohr effect) and that th

43、is is an important factor in increasing oxygen transport. 89The reverse is also true: binding of oxygen with hemoglobin tends to displace carbon dioxide from the blood. Indeed, this effect, called the Haldane effect, is quantitatively far more important in promoting carbon dioxide transport than is

44、the Bohr effect in promoting oxygen transport.90第四節(jié) 呼吸運動的調(diào)節(jié)91一. 呼吸中樞與呼吸節(jié)律的形成（一）呼吸中樞921、脊髓脊髓中支配呼吸肌的運動神經(jīng)元位于第3-5頸段（支配膈?。┖托囟危ㄖ淅唛g肌和腹肌等）前角。932、下位腦干 延髓和腦橋呼吸節(jié)律產(chǎn)生于低(下)位腦干。9495腦橋上部有呼吸調(diào)整中樞：相對集中于臂旁內(nèi)側(cè)核（NPBM)和 KF 核（合稱PBKF核群）。其主要的作用是限制吸氣，促使吸氣轉(zhuǎn)為呼氣。96關(guān)于長吸中樞（腦橋中下部）目前趨于否定。973、高位腦腦橋以上部位特別是大腦皮層大腦皮層對呼吸的調(diào)節(jié)系統(tǒng)是通過軀體運動神經(jīng)。 。下

45、位腦干的呼吸調(diào)節(jié)系統(tǒng)是自主節(jié)律呼吸調(diào)節(jié)系統(tǒng).它們的下行通路是分開的。98It is divided into three major collections of neurons: 1A dorsal respiratory group, located in the dorsal portion of the medulla, which mainly causes inspiration; 992 .A ventral respiratory group, located in the ventrolateral part of the medulla, which can cause e

46、ither expiration or inspiration, depending on which neurons in the group are stimulated; 1003 The pneumotaxic center呼吸調(diào)整中樞, located dorsally in the superior portion of the pons, which helps control the rate and pattern of breathing. The dorsal respiratory group of neurons plays the most fundamental

47、role in the control of respiration. 101 Neural Control of BreathingThe nervous system normally adjusts the rate of alveolar ventilation almost exactly to the demands of the body so that the oxygen pressure (PO2) and carbon dioxide pressure (PCO2) in the arterial blood are hardly altered even during

48、exercise and most other types of respiratory stress.102Central control of breathing Respiratory CenterThe respiratory center is composed of several groups of neurons located bilaterally in the medulla oblongata and pons, as shown for one side in Figure below.103Cerebral cortex Breathing can be under

49、 voluntary control; therefore, a person can voluntarily hyperventilate or hypoventilate.104二、呼吸的反射性調(diào)節(jié)肺牽張反射（黑-伯反射）(Hering-Breuer reflex)1051、肺擴張反射是肺充氣或肺擴張引起的吸氣抑制。感受器位于氣管到支氣管的平滑肌中。 肺擴張肺牽張感受器 興奮呼吸中樞吸氣停止，引起呼氣 。 迷走神經(jīng)106意義：防止吸氣過深，促進吸氣向呼氣轉(zhuǎn)化，調(diào)節(jié)呼吸頻率和深度。1072、肺縮小反射肺縮小或肺萎陷引起的吸氣反射。肺縮小肺泡及細支氣管牽張感受器迷走神經(jīng)呼吸中樞呼氣停止，轉(zhuǎn)為吸

50、氣108The Hering-Breuer Inflation ReflexStretch receptors are located in the muscular portions of the walls of the bronchi and bronchioles throughout the lungs. they transmit sensory nerve signals through the vagi into the dorsal respiratory group of neurons when the lungs become overstretched. 109The

51、se signals affect inspiration in much the same way as signals from the pneumotaxic center; that is, when the lungs become overly inflated, the stretch receptors activate an appropriate feedback response that switches off the inspiratory process and thus stops further inspiration. This is called the

52、Hering-Breuer inflation reflex. This reflex also increases the rate of respiration, the same as is true for signals from the pneumotaxic center.110三、呼吸的化學(xué)反射性調(diào)節(jié)（一）化學(xué)感受器1、外周化學(xué)感受器 111頸動脈體和主動脈體：對PO2降低， PCO2升高 及 pH下降 敏感,受到刺激，反射性地引起呼吸加深加快 。112 2、中樞化學(xué)感受器位于延髓腹外側(cè)，其有效刺激是腦脊液和局部細胞外液的H+，不感受局部CO2 血氫離子和缺O(jiān)2的刺激。113（

53、二）CO2對呼吸的影響 一定水平的PCO2對維持呼吸和呼吸中樞的興奮性是必要的，CO2是調(diào)節(jié)呼吸的最重要的生理性體液因子。114吸入氣 CO2 4% 肺通氣量增加1倍吸入氣 CO2 7% CO2 麻醉現(xiàn)象115CO2刺激呼吸是通過兩條途徑實現(xiàn)的，一是通過刺激中樞化學(xué)感受器,二是刺激外周化學(xué)感受器反射性地使呼吸加深、加快。但兩條途徑中前者是主要的。 116血液中的CO2能迅速通過血腦屏障，使化學(xué)感受器周圍液體中的H+升高，從而刺激中樞化學(xué)感受器，再引起呼吸中樞的興奮。117PCO2外周化學(xué)感受器（20%）中樞化學(xué)感受器（80%）呼吸中樞呼吸加深，加快118119H+對呼吸的調(diào)節(jié)也是通過外周化學(xué)感

54、受器和中樞化學(xué)感受器實現(xiàn)的,以前者為主。H+通過血液屏障的速度慢，限制了它 對中樞化學(xué)感受器的作用。（三） H+對呼吸的影響120p H外周化學(xué)感受器呼吸中樞呼吸加深，加快121低O2對呼吸的刺激作用完全是通過外周化學(xué)感受器實現(xiàn)的。122當(dāng)缺氧不甚嚴重時，低O2對中樞的直接作用是壓抑。低O2可以通過對外周化學(xué)感受器的刺激而興奮呼吸中樞以對抗低O2的直接壓抑作用。123不過在嚴重低O2時，外周化學(xué)感受性反射已不足以克服低O2對中樞的壓抑作用，終將導(dǎo)致呼吸障礙。 124（四）低O2對呼吸的影響PO2外周化學(xué)感受器呼吸中樞+-當(dāng)40mmHgPO280mmHg呼吸加深加快 當(dāng)PO240mmHg呼吸抑制

55、125CHEMICAL CONTROL OF RESPIRATIONThe ultimate goal of respiration is to maintain proper concentrations of oxygen, carbon dioxide, and hydrogen ions in the tissues. It is fortunate, therefore, that respiratory activity is highly responsive to changes in each of these.126Excess carbon dioxide or exce

56、ss hydrogen ions in the blood mainly act directly on the respiratory center itself, causing greatly increased strength of both the inspiratory and the expiratory motor signals to the respiratory muscles.127Oxygen, in contrast, does not have a significant direct effect on the respiratory center of th

57、e brain in controlling respiration. Instead, it acts almost entirely on peripheral chemoreceptors located in the carotid and aortic bodies, and these in turn transmit appropriate nervous signals to the respiratory center for control of respiration.128 Chemoreceptors for CO2, H+, and O2 1.Central chemoreceptors in the medullaa sensitive chemosensitive area, shown in figure below, is located bilaterally lying only one-fifth millimeter beneath the ventral surface of the medulla. 129130The sensor neurons in the chemosensiti