181; 218; 206; 229; 213; 194; 186; 244; 206; 252; respiration 浙江大學(xué)教學(xué)信息化平臺(tái)

1、Tissue capillariesTissue cellsCO2CO2O2O2Pulmonary capillaryCO2CO2O2O2Pulmonary gas exchangeTissue gas exchangeBoyles law states that the pressure of a fixednumber of gas molecules is inversely proportional to the volume of the container.MWdATSPDIn the lungs, the concentration gradients favor the dif

2、fusion of oxygen toward the blood and the diffusion of carbon dioxide toward the alveolar air; owing to the metabolic activities of cells, these gradients are reversed at the interface of the blood and the active cells.surfactantepithelial cellinterstitial spacealveoluscapillaryred blood cellendothe

3、lial cellVA/QC Effect of gravity on V/QPhysiologic dead spacePhysiologic shuntNormalMismatching of the air supply and blood supply in individual alveoli. The main effect of ventilation-perfusion inequality is to decrease the of systemic arterial blood.Hemoglobin is the gas-transport molecule inside

4、erythrocytes.Oxygen binds to the iron atom. Heme attaches to a polypeptide chain by a nitrogen atom to form one subunit of hemoglobin. Four of these subunits bind to each other to make a single hemoglobin molecule.Hb + O2 HbO2 High PO2Low PO2As the concentration of oxygen increases, the percentage o

5、fhemoglobin saturated with bound oxygen increases until allof the oxygen-binding sites are occupied (100% saturation).Note that venous blood is typically 75% saturated with oxygen.Chemical and thermal factors that alter hemoglobins affinity to bind oxygen alter the ease of “l(fā)oading”and “unloading” t

6、his gas in the lungs and near the active cells.Chemical and thermal factors that alter hemoglobins affinity to bind oxygen alter the ease of “l(fā)oading”and “unloading” this gas in the lungs and near the active cells.High acidity and low acidity can be caused by high tissue capillariestissuesCO2 + HbHb

7、CO2CO2tissue capillariesCO2 + H2OH2CO3H+ +HCO3-carbonic anhydraseCO2pulmonary capillariesCO2 + HbHbCO2H+ +HCO3-H2CO3carbonic anhydraseCO2 + H2OCl-pulmonary capillariesCO2 Oxidation GlycolysisCell RespirationBasic respiratory center: produce and control the respiratory rhythm The discharge of medulla

8、ry inspiratory neurons provides rhythmic input to the motor neurons innervating the inspiratory muscles. Then the action potential cease, the inspiratory muscles relax, and expiration occurs as the elastic lungs recoil. Chemosensory neuronsthat respond to changesin blood pH and gas content are locat

9、ed in the aorta and in thecarotid sinuses; thesesensory afferentneurons alter CNSregulation of the rate of ventilation.Small changes in thecarbon dioxide contentof the blood quickly trigger changes in ventilation rate.CO2 respiratory activityCentral and peripheralchemosensory neurons that respond to

10、 increased carbon dioxide levels in the blood are also stimulated by the acidity from carbonic acid, so they “inform” the ventilation control center in the medulla to increase the rate of ventilation. Regardlessof the source,increases in the acidity ofthe blood cause hyperventilation.H+ respiratory

11、activityRegardless of the source, increases in the acidity of the blood cause hyperventilation, even if carbon dioxide levels are driven to abnormally low levels.A severe reduction in the arterial concentration of oxygen in the blood can stimulate hyperventilation.PO2 respiratory activityChemosensory neuronsthat respond to decreasedoxygen levels in the blood“inform” the ventilation control center in themedulla to increase the rate of ventilation.The levels ofoxygen, carbondioxide, and hydrogen ionsin blood and CSFprovide informationth