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Respiration

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  1. Respiration

  2. 2/12 Overview of gas exchange • Lavoisier some 200 years ago described that animal life and burning both use O2 and produce CO2 • his reward was the guillotine in 1794 at the age of 51, as he also happened to be a tax-collector • oxygen is taken up by diffusion – factors: surface, gradient, distance • in multicellular organisms surface/volume ratio decreases – respiratory organs must have large surface • distance should be minimal – thin, vulnerable barrier (0,5 - 15 ) • gradient should be large – respiratory movements, circulation, blood pigments  • in humans the respiratory surface is 50-100 m2, rest of the body: 2 m2 Eckert: Animal Physiology, W.H.Freeman and Co., N.Y.,2000, Fig. 13-1.

  3. 3/12 Anatomy of the lung I. • 2 halves, 900-1000 g together, right half is somewhat larger, 40-50 % blood • airways: • trachea – bronchi – bronchioles – alveolar ducts - alveoli • branching is always fork-like, crosssectional area of the two „child” bronchi is always larger - 22-23 branching • trachea and large bronchi (up to 1 mm) are supported by C-shaped, or irregular plates of cartilage • below 1 mm – bronchioles, connective tissue and muscle • function: warming, saturation with water vapor (exspiration in cold, dehydration in dry air) • exchange of gases occurs in alveolar duct-alveolus (300 million) - surface 50-100 m2 • during evolution more and more septum in this part – surface increase • emphysema – heavy smokers, trumpet players, glass blowers • barrier: endothel, epithel, fibers Eckert: Animal Physiology, W.H.Freeman and Co., N.Y.,2000, Fig. 13-21, 22.

  4. 4/12 Anatomy of the lung II. • lungs are covered by the parietal and visceralpleuras • thin fluid layer (20 ) couples the pleuras (pleuritis, pneumothorax, treatment of tuberculosis) • the lung has a collapsing tendency (surface tension + elastic fibers) • surfactant in alveoli (produced by epithelial cells: dipalmitoyl-phosphatidylcholine) • respiratory muscles: • inspiration active, exspiration passive normally • intercostal muscles, T1-11, external: inspiration, internal: exspiration • diaphragm, C3-5 (n. phrenicus), at rest 1-2 cm movement: 500 ml, it can be 10 cm – damage of the spinal chord – jumping into shallow water! • abdominal wall (birthday candles, trumpet, always important above 40/minute) • accessory muscles – help inspiration in case of dispnoe  Eckert: Animal Physiology, W.H.Freeman and Co., N.Y.,2000, Fig. 13-31.

  5. lung volumes can be measured by spirometers - spirogram anatomicalandphysiologicaldead space in swans and giraffes it is huge, large tidal volume tidal volume (500 ml) – anatomical dead space (150 ml) = 350 ml dilutes functional residual volume: steady O2 concentration total ventilation: 14 x 350 ml = 4900 ml/minute 5/12 Lung volumes Eckert: Animal Physiology, W.H.Freeman and Co., N.Y.,2000, Fig. 13-23.

  6. 6/12 Gas concentrations atmospheric pressure: 760 mmHgpartial pressure of water vapor: 47 mmHg * effect of O2consumption, and anatomical dead space ** bronchiolar veins join here

  7. 7/12 Transport of O2 I. • physical solubility of O2is very low – 0.3/100 ml • rainbow trout lives only in fast mountain streams • when lakes (i.e. Balaton) warm up, fish can die (decomposing organic materials also use up O2) • some fish (e.g. carp) can swallow air • hemoglobin increases O2 solubility 70-fold - 20 ml/100 ml  • oxyhemoglobin bright red, deoxyhemoglobindark red-purple – see difference of venous and capillary blood during blood tests • some invertebrates also have hemoglobin, others copper-containing hemocyanin (gastropods, arthropods) - extracellular • affinity is chracterized by half staruration: Hgb: 30 mmHg, myoglobin 5 mmHg • saturation of Hgb at 100 mmHg 97.4%, at 70 mmHg 94.1% - almost no change  Eckert: Animal Physiology, W.H.Freeman and Co., N.Y.,2000, Fig. 13-3. Eckert: Animal Physiology, W.H.Freeman and Co., N.Y.,2000, Fig. 13-2.

  8. 8/12 Transport of O2 II. • O2 affinity of Hgb controls plasma concentration • in the lung, high affinity is advantageous to keep plasma concentration low • in the tissues, low affinity is advantageous to keep plasma concentration high • affinity is decreased by: • increased temperature – active tissues are warmer • decrease of pH, increase of CO2 - applies to active tissues and organs • Bohr’s-effect: H+uptake - affinitydecreases, on the other hand uptake of O2increases acidityHaldane’s-effect • organic phosphate ligands, e.g.ATP, GTP, 2,3-bisphosphoglycerate (BPG) • BPG increases when O2decreases, or pH increases – in highmountains hyperventilation because of the low O2 - pH increases, O2 affinity increases, release of O2 (desaturation) in the tissues is difficult - BPG restores affinity • in stored blood, BPG is low – large volume transfusion of such blood – release of O2 insufficient Eckert: Animal Physiology, W.H.Freeman and Co., N.Y.,2000, Fig. 13-4.

  9. 9/12 Transport of O2 III. • O2 affinity depends on the chain composition of the Hgb (4 peptid chains): in the fetus chain instead of  - higher affinity • methemoglobin contains Fe+++ ion instead of Fe++ - cannot bind oxygen • enzyme in red blood cells reduces iron back - nitrite and other inorganic ions increase Fe+++ amount either directly or by enzyme inhibition • carboxyhemoglobin - CO binds to hemoglobin, affinity 200-fold, half-saturation at 0.1 mmHg – very dangerous (car exhaust) • sickle cell anemia - valine/glutamate change in the  chain – sickle shape, cannot pass through small capillaries - O2 supply deteriorates – but defends against malaria • 70-200 ml blood in the lung capillaries spread on 70 m2 – fast gas exchange • red blood cell stays for 750 ms in the capillary – saturated in 250 ms with O2 – spare time!

  10. 10/12 Transport of CO2 • CO2 is more soluble physically, but it also reacts with water • transport mainly in the form of HCO3- (88-90%), some as CO2, H2CO3, or CO32-, some attached to proteins (carbamino)  • most of the released CO2 fromHCO3- (80%) • CO2 - H2CO3 transformation is slow (several seconds) – carbonic anhydrase enzyme inside the red blood cell – speeds up reaction • H+ ion is taken up by the deoxyhemoglobin that is weaker acid than the oxyhemoglobin • HCO3- is exchanged for Cl- - facilitated diffusion with antiporter - Hamburger-shift • opposite process in the lungs  Eckert: Animal Physiology, W.H.Freeman and Co., N.Y.,2000, Fig. 13-9. Eckert: Animal Physiology, W.H.Freeman and Co., N.Y.,2000, Fig. 13-11.

  11. 11/12 Regulation of breathing I. • mammals use 5-10% of all energy consumption for the perfusion and ventilation of the lung • closely matched processes to avoid wasted perfusion or ventilation • alveolar hypoxia - local vasoconstriction • in high mountains low O2, general constriction – increased resistance – higher blood pressure in pulmonary artery – lung edema • central regulation: inspiratory and expiratory neurons in the medulla – other functions as well, thus not a center • dorsomedial neurons, close to the nucl. tractus solitarius: inspiratory neurons • ventrolateral expiratory neurons • in the pons “pneumotaxic center”:role is less clear • descending effects: talking, singing, crying, laughing, etc.

  12. 12/12 Regulation of breathing II. • output: motoneurons innervating the diaphragm and the intercostal muscles • trigger for inspiration: • increase of CO2 and H+ - central receptors;no breathing below a certain CO2 threshold • decrease of O2 , increase of CO2 and H+ - glomus caroticum and aorticum • in terrestrial animals CO2 is regulated, in aquatic animals O2 – its concentration changes more; if O2 exchange is sufficient, than that of the more soluble CO2 should be also OK • trigger for expiration: stretch receptors in the lungs - Hering-Breuer reflex  • these information serve not only gas exchange and pH regulation, but such reflexes as swallowing, coughing, etc. Eckert: Animal Physiology, W.H.Freeman and Co., N.Y.,2000, Fig. 13-49.

  13. End of text

  14. Overview of gas exchange Eckert: Animal Physiology, W.H.Freeman and Co., N.Y.,2000, Fig. 13-1.

  15. The mammalian lung Eckert: Animal Physiology, W.H.Freeman and Co., N.Y.,2000, Fig. 13-21, 22.

  16. Respiratory muscles Eckert: Animal Physiology, W.H.Freeman and Co., N.Y.,2000, Fig. 13-31.

  17. Structure of hemoglobin Eckert: Animal Physiology, W.H.Freeman and Co., N.Y.,2000, Fig. 13-2.

  18. Saturation of hemoglobin Eckert: Animal Physiology, W.H.Freeman and Co., N.Y.,2000, Fig. 13-3.

  19. Bohreffect Eckert: Animal Physiology, W.H.Freeman and Co., N.Y.,2000, Fig. 13-4.

  20. CO2 transport Eckert: Animal Physiology, W.H.Freeman and Co., N.Y.,2000, Fig. 13-9.

  21. Red blood cells in CO2 transport Eckert: Animal Physiology, W.H.Freeman and Co., N.Y.,2000, Fig. 13-11.

  22. Activity of the phrenic nerve Eckert: Animal Physiology, W.H.Freeman and Co., N.Y.,2000, Fig. 13-49.