Lecture 19, 04 Nov 2003 Chapter 13, Respiration, Gas Exchange, Acid-Base Balance. Vertebrate Physiology ECOL 437 University of Arizona Fall 2003

Transcription

1 1 Lecture 19, 04 Nov 003 Chapter 13, Respiration, Gas Exchange, Acid-Base Balance Vertebrate Physiology ECOL 437 University of Arizona Fall 003 instr: Kevin Bonine t.a.: Bret Pasch

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

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

5 Gravity and BP 5 Knut Schmidt_Nielsen 1997

6 6 Cardiac Output 6x Exercise Oxygen Consumption X 0 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 pp at 760 mm Hg mmHg (at 6000m) Solubility in water (ml/l) 34 1, Why is po in lungs less than expected?

9 Effects of Temp and Solutes on O solubility 9 Temp (C) Fresh Sea 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 < (amt. needed to get O ) Movement of medium tidal unidirectional (take in, (less energy expel) required)

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

12 13-1 1

13 Gas transport in blood 13 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 98% of O transported via carrier molecules

14 hemoglobin hemocyanin hemerythrin Metal Fe Cu Fe 14 Distribution over 10 phyla phyla 4 phyla (all verts, many inverts) (arthropods, mollusks) Location RBCs (verts) dissolved in intracellular plasma Color deox maroon colorless colorless ox red blue reddish violet

15 15 Hemoglobin and other Respiratory Pigments Knut Schmidt_Nielsen 1997

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

17 hemoglobin Fetal hemoglobin: 17 γ chains (not β) w/ higher affinity for O (enhance O transfer from mother to fetus) Affinity for CO = 00 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

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

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

20 Factors that reduce affinity 0 1. low ph (increase [H+]). increase in CO 3. elevated Temp 4. organic compounds

21 Factors that reduce affinity 1 1. and. Increase in [CO ] or [H+] 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)

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

23 3 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 Factors that reduce affinity 4 4. organic compounds organophosphates in erythrocytes differ among spp. mammals:,3 DPG birds: IP 3 fish: ATP, GTP bind to hemoglobin as allosteric effectors used to maintain O affinity under hypoxic conditions at high altitude (low blood [O ]) increase,3 DPG to increase delivery of O to tissues

25 5 CO transport in blood + CO + H O H CO H + HCO - CO + OH HCO 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 3 3 (bound to amino groups of hemoglobin)

26 Haldane effect 6 deox hemo has high affinity - for H creating inc. [HCO ] in 3 blood (more CO ) + recall equations on previous slide

27 7 Bohr effect + Haldane effect increasing [CO ] decreases affinity of hemoglobin for O, so binds CO more easily

28 CO transfer at tissue enters/leaves blood as CO (more rapid diffusion) passes thru RBCs CO produced = O released no change in ph -Chloride Shift -Carbonic Anhydrase 8 oxygenation of hemo: acidify interior (release H + ) only in RBC, not plasma Band III protein passive exchange, bidirectional maintain charge balance deox of hemo: + inc ph (bind H )

29 CO transfer at lung 9 facilitated diffusion Acidify RBC: facilitate HCO - CO 3 - dec. in HCO in 3 RBC: influx

30 Acid-Base balancing 30 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 small overall effect on ph excreted continually via kidneys, gills, skin build-up of CO build-up of H + (acidify body) low CO low H + (alkaline body) +

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 Respiration and ph inc. lung ventilation (low body [CO ]) inc ph respiratory alkalosis buffer: kidney dec. ph by excreting HCO- 3 dec. lung ventilation (CO excretion dec.) dec. ph respiratory acidosis

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

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

34 Maintaining ph balance in the body 34 (acid production = acid excretion) Mammals: adjust CO excretion via lungs - 3 acid/hco excretion via kidneys

35 35 Jackson et al. 000 Apalone - softshell turtle Chrysemys - painted turtle Mg+, Ca+ (weak base carbonates) Lactic acid bone sequestration anoxia

36 Lung Anatomy 36 Nonrespiratory -Trachea -> -Bronchi -> -Bronchioles -> (13-1) Respiratory -Terminal bronchioles -> -Respiratory bronchioles -> -Alveoli -Cilia and Mucus

37 -Gas Diffusion Barriers: 37 (13-)

38 Lung Ventilation 38 -Small mammals with greater per gram O needs and therefore greater per gram respiratory surface area -Dead Space (anatomic and physiological) Swan (13-4)

39 Lung Ventilation 39 (13-3)

40 End