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Lecture 19, 04 Nov 2003 Chapter 13, Respiration, Gas Exchange, Acid-Base Balance Vertebrate Physiology ECOL 437 Universi

1. Lecture 19, 04 Nov 2003 Chapter 13, Respiration, Gas Exchange, Acid-Base Balance Vertebrate Physiology ECOL 437 University of Arizona Fall 2003 instr: Kevin Bonine t.a.: Bret Pasch. 2. Vertebrate Physiology 437. VOTE!. 1. Blood-Gas Chemistry (CH13) 2. Announcements. 3.

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Lecture 19, 04 Nov 2003 Chapter 13, Respiration, Gas Exchange, Acid-Base Balance Vertebrate Physiology ECOL 437 Universi

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  1. 1 Lecture 19, 04 Nov 2003 Chapter 13, Respiration, Gas Exchange, Acid-Base Balance Vertebrate Physiology ECOL 437 University of Arizona Fall 2003 instr: Kevin Bonine t.a.: Bret Pasch

  2. 2 Vertebrate Physiology 437 VOTE! 1. Blood-Gas Chemistry (CH13) 2. Announcements...

  3. 3 Term Paper Draft due Thursday 06 Nov. Turn in old, relevant, graded work. On the actual most recent draft use a CODE NAME so your paper can be anonymously reviewed by one of your peers. We will give you a paper to edit/review at the end of class on Thursday

  4. 4 Name that student: Jane Davis Hematology Oncology French Katie Cox Tall Kim Hurd Air Force ROTC

  5. 5 Gravity and BP Knut Schmidt_Nielsen 1997

  6. 6 Cardiac Output 6x Exercise Oxygen Consumption X 20 Knut Schmidt_Nielsen 1997

  7. 7 Chapter 13 – Blood-Gas Chemistry Oxygen and Carbon Dioxide - Air vs. Water - Epithelial Transfer - Transport and Regulation pH regulation Chloride shift Carbonic Anhydrase Elevation Skip: Diving, Swimbladder, Exercise

  8. 8 Gas composition in air O CO N % of dry air 21 0.03 78 pp at 760 mm Hg 159 0.23 594 380mmHg (at 6000m) 79.6 0.11 297 Solubility in water (ml/L) 34 1,019 17 2 2 2 Why is pO2 in lungs less than ‘expected’?

  9. 9 Effects of Temp and Solutes on O solubility 2 Temp (C) Fresh Sea 0 10.29 7.97 10 8.02 6.60 20 6.57 5.31 Increase in temp Increase [ion] decrease solubility

  10. 10 Rate of diffusion depends on molecular weight (Graham’s Law) Air Water O solubility > O rate of diffusion > Weight of medium < Movement of medium tidalunidirectional 2 2 (amt. needed to get O ) 2 (take in, expel) (less energy required)

  11. 11 Gas transfer 1. Breathing (supply air or water to respiratory surface) 2. Diffusion of O & CO across resp. epithelium 3. Bulk transport of gases by blood 4. Diffusion across capillary walls (blood mitochondria) 2 2 (humans = 50-1002 m SA)

  12. 12 13-1

  13. 13 Gas transport in blood Respiratory pigments • all have either Fe or Cu ions that O binds • pigment increases O content of blood • complex of proteins and metallic ions • each has characteristic color that changes w/ O content • ability to bind to O (affinity) affects carrying capacity of blood for O 2+ 2+ 2 2 2 2 2 98% of O transported via carrier molecules 2

  14. 14 hemoglobinhemocyaninhemerythrin 2+ 2+ 2+ Metal Fe Cu Fe Distribution over 10 phyla 2 phyla 4 phyla (all verts, many inverts) (arthropods, mollusks) Location RBCs (verts) dissolved in intracellular plasma Color deox – marooncolorlesscolorless ox – red blue reddish violet

  15. 15 Hemoglobin and other Respiratory Pigments Knut Schmidt_Nielsen 1997

  16. 16 hemoglobin 4 heme + 4 protein chains can carry 4 O 2 heme molecules

  17. hemoglobin 17 Fetal hemoglobin: γ chains (not β) w/ higher affinity for O (enhance O transfer from mother to fetus) Affinity for CO = 200 x’s greater than for O CO poisoning even at low partial pressures Antarctic icefish lack pigment low metabolic needs = low metabolism high cardiac output, blood volume large heart 2 2 2

  18. 18 O dissociation curve 2 hyperbolic • sigmoidal • not need lots of O to get near 100% 2 Cooperativity -binding of 1st O2 facilitates more binding -oxygenation of 1st heme group increases affinity of remaining 3 for O2

  19. 19 P - pp of O at which pigment is 50% saturated 50 2 Pigment w/ High P : 50 • low affinity • high rate of O transfer to tissues 2 Pigment w/ Low P : 50 • high affinity • high rate of O uptake 2

  20. 20 Factors that reduce affinity 1. low pH (increase [H+]) 2. increase in CO2 3. elevated Temp 4. organic compounds

  21. 21 Factors that reduce affinity 1. and 2. Increase in [CO ] or [H+] 2 • Bohr effect • CO and H bind to hemoglobin (allosteric site), which • changes conformation of molecule and • changes binding site for O • at tissues: • CO binds to hemoglobin, decreasing affinity • for O , allowing better delivery of O • Root effect • fishes… (skip) + 2 2 2 2 2

  22. 22 Bohr Effect CO enters blood at tissues hemoglobin unloads O CO leaves blood at resp. surface hemoglobin uptake O 2 2 2 2 Carbonic acid Bicarbonate + - CO + H O H CO H + HCO 2 2 2 3 3 Inc in Pco inc [H+] dec pH reduces affinity 2

  23. 23 Bohr shift as a function of body size (small animals with greater Bohr shift [more acid sensitive] so can more readily leave oxygen at tissues at given PO) Knut Schmidt_Nielsen 1997

  24. 24 Factors that reduce affinity 4. organic compounds • organophosphates in erythrocytes differ among spp. • mammals: 2,3 DPG • birds: IP • fish: ATP, GTP 3 • bind to hemoglobin as allosteric effectors • used to maintain O affinity under hypoxic conditions • at high altitude (low blood [O ]) increase 2,3 DPG to increase delivery of O to tissues 2 2 2

  25. 25 CO transport in blood 2 - CO + H O H CO H + HCO CO + OH HCO + 2 2 2 3 3 - - 2 3 - Proportions of CO , HCO depend on pH, T, ionic strength of blood At normal pH, Temp: 80% of CO in form of bicarbonate ion HCO 5-10% dissolved in blood 10% in form of carbamino groups (bound to amino groups of hemoglobin) 2 3 - 2 3

  26. 26 Haldane effect • deox hemo has high affinity for H creating inc. [HCO ] in blood (more CO ) • recall equations on previous slide - + 3 2

  27. 27 Bohr effect + Haldane effect increasing [CO2 ] decreases affinity of hemoglobin for O2 , so binds CO2 more easily

  28. CO transfer at tissue -Chloride Shift -Carbonic Anhydrase 28 2 • enters/leaves blood as CO (more rapid diffusion) • passes thru RBCs • CO produced = O released no change in pH 2 2 2 oxygenation of hemo: acidify interior (release H ) Band III protein + passive exchange, bidirectional maintain charge balance only in RBC, not plasma deox of hemo: inc pH (bind H ) +

  29. 29 CO transfer at lung 2 facilitated diffusion Acidify RBC: facilitate HCO CO2 - dec. in HCO in RBC: influx 3 - 3

  30. 30 Acid-Base balancing - + • Animal body pH: slightly alkaline (more OH than H ) • maintain pH for stability of proteins (and function) + H production / excretion • produced: metabolism of ingested food • ingest meat: acid • ingest plants: base • excreted continually via kidneys, gills, skin • build-up of CO build-up of H (acidify body) • low CO low H (alkaline body) small overall effect on pH + 2 + 2

  31. 31 pH buffers in blood: bicarbonate – not true buffer, but CO / HCO ratio imp. to pH excretory organs (kidneys, gills, skin) proteins (hemoglobin), phosphates CO + H O H CO H + HCO - 2 3 + - 2 2 2 3 3 Respiration and pH • inc. lung ventilation (low body [CO ]) inc pH • respiratory alkalosis • buffer: kidney dec. pH by excreting HCO • dec. lung ventilation (CO excretion dec.) dec. pH • respiratory acidosis 2 - 3 2

  32. 32 pH buffers If CO inc in extra., diffuse into cell to form HCO and dec. intracellular pH efflux of H , or influx of HCO leads to rise in pH 2 - 3 + - 3 via ATPase or coupled w/ Na influx + Muscle vs. Brain

  33. 33 Need to REDO: Response to acid load in cell: + • H efflux + Na influx (cation-exchange) • H passive diffusion out of cell • HCO influx + Cl efflux (anion-exchange) • H efflux = HCO influx • HCO inside cell CO + OH (inc. pH) • CO leaves cell to form HCO + H or both in plasma membrane + - - 3 + - 3 - - 3 2 • Jacob-Stewart cycle p.543 - + 2 3 • buffering via proteins/phosphates in cell

  34. 34 Maintaining pH balance in the body (acid production = acid excretion) Mammals: adjust CO excretion via lungs acid/HCO excretion via kidneys 2 - 3

  35. 35 Jackson et al. 2000 Apalone - softshell turtle Chrysemys - painted turtle Mg+, Ca+ (weak base carbonates) Lactic acid bone sequestration anoxia

  36. 36 • Lung Anatomy • Nonrespiratory • Trachea -> • Bronchi -> • Bronchioles -> • Respiratory • Terminal bronchioles -> • Respiratory bronchioles -> • Alveoli (13-21) -Cilia and Mucus

  37. 37 -Gas Diffusion Barriers: (13-22)

  38. 38 Lung Ventilation -Small mammals with greater per gram O2 needs and therefore greater per gram respiratory surface area -Dead Space (anatomic and physiological) Swan (13-24)

  39. 39 Lung Ventilation (13-23)

  40. End

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