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22nd LectureFri 06 Mar 2009

Vertebrate PhysiologyECOL 437 (MCB/VetSci 437)Univ. of Arizona, spring 2009

Kevin Bonine & Kevin Oh

Oxygen, Carbon DioxideRespirationGas TransportChapter 21-23

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Housekeeping, Fri 06 March 2009

ReadingsToday: Ch 21 (oxygen, carbon dioxide) Mon 09 Mar: Ch 22 (respiration)Wed 11 Mar: Ch23 (gas transport)Fri 13 Mar: Second Midterm 14-22 March Spring Break

Lab discussion leaders: xx1pm – xx3pm – xx

Lab discussion leaders: 25 Mar1pm – Sam3pm – Karri, Jason

Fri 13 Feb = Exam 1

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GasesFoodSalts

WaterWaste(Temp)

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7Hill et al., 2004, Fig. 20.6

Oxygen needed for cellular respirationMake ATP

8Hill et al., 2004, Fig. 20.1

21% Oxygen in Air

Partial Pressure = Total Pressure x Percent Composition

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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

Partial Pressures

sea level

10Hill et al., 2004

Cold Air/Water holds More Oxygen

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11Hill et al., 2004, Fig. 20.5

Oxygen Partial Pressure Decreasesfrom Air to Mitochondria

Why is pO2 in lungs less than

‘expected’?

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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)

Gas Transfer

2 2(humans = 50-1002 m SA)

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1. Breathing

2. Diffusion

3. Bulk transport

4. Diffusion Mitochondria

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Fick’s Law of Diffusion

Q=kAP2-P1

DQ =rate of diffusionk =diffusion coefficient (varies)A =x-sectional area for diffusionP2-P1 = pressure gradientD = distance to diffuse across

Why did circulatory systems evolve?

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Fick Equation

Which of these will increase rate of diffusion of a gas like oxygen:

A – Increasing distance (D) across which gas must travel

B – Increasing P1 relative to P2C – Increase area (A) across which gas movesD – Changing from air to water (~k)E – Decreasing P2 relative to P1

Q=kAP2-P1

D

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Rate of DiffusionAir Water

O solubility >

O rate of diffusion >

Weight of medium <

Movement of medium tidal unidirectional

(amt. needed to get O )

(take in, expel)

(less energy required)

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2

2

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In flatworm, all cells are within 1mm of water

No need for circulatory system

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Hill et al., 2004, Fig. 21.8

Some Gas ExchangeAcrossSkin

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19Knut Schmidt_Nielsen 1997

Lake Titicaca Frog

(Bolivian Navy; Peru-Bolivia border)

20Hill et al., 2004, Fig. 20.4

Circulatory System allowed Animals to get BIGGER

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21Hill et al., 2004, Fig. 21.1

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(Eckert, 13-22)

Membranes and Fluids are Gas Diffusion Barriers:

Why canpneumonia kill

you?

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23Hill et al., 2004, Fig. 20.4

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Mammalian Ventilation

-lungs are elastic bags

-suspended in pleural cavity within thoracic cage (ribs and diaphragm define, fluid lines)

-low volume pleural “space” between lung and thoracic wall

-negative pressure to inflate lungs (increase volume)

-pneumothorax

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Mammalian Ventilation (Eckert, 13-28)

-negative pressure to inflate lungs (increase volume)

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Mammalian Ventilation

(Eckert, 13-30)

-expiration usually passive

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Frog Ventilation

-Positive pressure

1. Into mouth (buccal cavity)

2. Close nares, open glottis and force air into lungs by raising buccal floor

(Eckert, 13-33)

28Knut Schmidt_Nielsen 1997

MammalianLung

Alveoli and Capillaries

RBC (not to scale)

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Lung Anatomy

Nonrespiratory-Trachea ->-Bronchi ->-Bronchioles ->

Respiratory-Terminal bronchioles ->-Respiratory bronchioles ->-Alveoli

-Cilia and Mucus

(Eckert, 13-21)

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Lung Ventilation

-Small mammals with greater per gram O2 needs and therefore greater per gram respiratory surface area?

-Dead Space (anatomic and physiological)

Swan (Eckert, 13-24)

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31(Eckert, 13-23)

Lung Ventilation

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Pulmonary Surfactants-Reduce liquid surface tension in alveoli

-Lipoproteins

-keep alveoli from getting stuck closedAtelectasis = collapsed lung

-premature babies may need artificial surfactant

-Allows for compliance and low-cost expansion of lung

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33Knut Schmidt_Nielsen 1972

Panting Dogs?

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Rate and Depth Regulation -Primarily via CO2changes (central)

O2 ~controls respiration in aquatic vertebrates, Why?

(Eckert, 13-46)

-Innervate MedullaryRespiratory Center(phrenic nerve to diaphragm and intercostals)

-Peripheral Chemoreceptors

PO2, PCO2, pH(Vagus nerve to medulla oblongata)

-Emotions, sleep, light, temperature, speech, volition, etc.

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Rate and Depth Regulation

(Eckert, 13-48)

-Central Chemoreceptors

Long term

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To Diaphragm

alveolar

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Hering-Breuer reflex

-Stimulation of stretch receptors inhibits medullary inspiratory center

-Prevent overinflation

-Ectotherms often breathe intermittently

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(Eckert, 13-45)

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1

2

2

To Diaphragm

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39Knut Schmidt_Nielsen 1997

Bird Lung Ventilation

Unidirectional!!

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Bird Ventilation

(Eckert,13-32)

-lung volume changes very little, air sacs instead

Unidirectional

(Eckert,13-32)

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Knut Schmidt_Nielsen 1972

Bird LungParabronchi

Mammal LungAlveoli

42Knut Schmidt_Nielsen 1997

Fish Gill

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43Hill et al., 2004, Fig. 21.10

Fish Gills

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Knut Schmidt_Nielsen 1997

Fish Gill

-breathing in water-need much higher ventilation rate

-unidirectional-pump water across gills (or ram ventilation)

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45Hill et al., 2004, Fig. 20.3

unidirectional tidal

Why aren’t fish gills tidal?

46Knut Schmidt_Nielsen 1997

Relative Gill Surface Area in Fishes

high

low

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47Hill et al., 2004, Fig. 21.7

Animals with higher oxygen needs increase diffusion area

48Hill et al., 2004, Fig. 21.7

Animals with higher oxygen needs reduce

diffusion distances

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49Hill et al., 2004, Fig. 21.4

How could you design a pair of vessels in the gill for more

efficientexchange?

waterConcurrent

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Counter-Current Exchangers

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51Hill et al., 2004, Fig. 21.5

Cross-current

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Vertebrate

Gas Transport

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53Hill et al., 2004, Fig. 21.4

Hill et al., 2004, Fig. 21.3

Oxygen Transport

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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

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98% of O transported via carrier molecules

Gas transport in blood

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2

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Hill et al., 2004, Fig. 22.4

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hemoglobin hemocyanin hemerythrin

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 – maroon colorless colorlessox – red blue reddish violet

2+ 2+ 2+

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57Knut Schmidt_Nielsen 1997

Hemoglobinand other Respiratory Pigments

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hememolecules

hemoglobin4 heme + 4 protein chains

can carry 4 O2

98% of O2transported via carrier molecules

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Hemoglobin Fun Facts:Fetal hemoglobin:

gamma 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

Antarctic icefish lack pigment

-low metabolic needs = low metabolism

-high cardiac output, blood volume

-large heart

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Oxygen dissociation curveHyperbolic (myoglobin)

Sigmoidal (Hemoglobin)-rate of binding changes

Hemoglobin Cooperativity:-binding of 1st O2 facilitates more binding-oxygenation of 1st heme group increases affinity of other 3 for O2

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61Hill et al., 2004, Fig. 22.6

Steep Part of Oxygen Dissociation Curve, Quickly Unload Oxygen

62Hill et al., 2004, Fig. 22.5

UNLOAD MORE oxygen when tissues NEED MORE

Why does partial pressure of

oxygen in tissuesdecrease with

exercise?

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Hill et al., 2004, Fig. 22.7

Sigmoidalvs. Hyperbolic

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Factors that reduce affinity

1. low pH (increase [H+])

2. increase in CO2

3. elevated Temp

4. organic compounds

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1. and 2. Increase in [CO ] or [H+]

Factors that reduce affinity

• 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

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2

2

2

2 2

+

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Bohr Effect

CO + H O H CO H + HCO 2 2 2 3

+3-

Inc in Pco inc [H+] dec pH reduces affinity2

CO enters blood at tissueshemoglobin unloads O

CO leaves blood at resp. surfacehemoglobin uptake O

2

2

2

2

Carbo

nic ac

id

Bicarb

onate

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Hill et al., 2004, Fig. 22.11Bohr Effect

68Knut Schmidt_Nielsen 1997

Bohr shiftas 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)

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Factors that reduce affinity

4. organic compounds • organophosphates in erythrocytes differ among spp.

mammals: 2,3 DPG

birds: IP

fish: ATP, GTP

• 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?

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2

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Carbon Dioxide Transport

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Hill et al., 2004, Fig. 22.20

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Hill et al., 2004, Fig. 22.21

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CO transport in blood2

CO2 + H2O H2CO3 H+ + HCO-3

Proportions of CO2 , HCO-3 depend on pH, T, ionic strength of blood

At normal pH, Temp:

80% of CO2 in form of bicarbonate ion HCO-3

5-10% dissolved in blood

10% in form of carbamino groups

(bound to amino groups of hemoglobin)

HCO-3 H+ + CO2-

3

CO2 + OH- HCO-3

bicarbonate

carbonate

carbonic acid

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Haldane effect

• deox hemo has high affinity for

H+ creating inc. [HCO3 ] in blood

(more CO2 )

• recall equations on previous slide

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Hill et al., 2004, Fig. 22.22Carbon Dioxide Transport:

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CO2 transfer at tissue• enters/leaves blood as CO2 (more rapid diffusion)

• passes thru RBCs

• CO2 produced = O2 released no change in pH

only in RBC, not plasma

maintain charge balance

oxygenation of hemo: acidify

interior (release H+ )

deox of hemo: increase pH (bind H+)

Band III protein

-Chloride Shift-Carbonic Anhydrase

(13-10)

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