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Lecture 22, 03 November 2005Wrap up Carbon Dioxide Transport

Begin Osmoregulation (Chapter 25-27)

Vertebrate PhysiologyECOL 437 (aka MCB 437, VetSci 437)

University of ArizonaFall 2005

instr: Kevin Boninet.a.: Kristen Potter

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1. CO2 transport2. Acid/Base Balance3. Osmoregulation4. Kidney Function

Text:Chapters 25-27

(Eckert 14-17)

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Push back seminar write-ups to 29 November if you wish.

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Hill et al., 2004, Fig. 22.20

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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-

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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. 22.21

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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

(Eckert 13-10)

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CO transfer at lung

dec. in HCO in RBC: influx

facilitated diffusion

Acidify RBC: facilitate

HCO CO2

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3- 3

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Jacob-Stewart Cycle

(Eckert 13-17)

Move acid in or out of RBC

(e.g., help buffer CO2 rise in plasma)

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Osmoregulation

• Eldon Braun Tuesday 08 Nov

Vertebrate Physiology 437

(Eckert, 14-18)

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Osmoregulation-Ionic and Osmotic Balance

-Kidney Function

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Osmoregulation

-life arose in salty sea-extracellular fluids ~ similar

-terrestrial organisms (and their descendents) regulate internal environment (homeostasis)

-salt and water regulation (waste excretion)

-dist’n limited by temperature and osmotic pressure(dehydration, ionic composition)

-kidneys, salt glands, gills

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Obligatory Osmotic Exchanges

2-Surface-to-Volume Ratio-Small animals dehydrate or hydrate more rapidly

-Skin, and Respiratory surface(higher metabolism with higher per/gramrespiratory surface)

3-Integument Permeability-Transcellular or Paracellular-Aquaporins = water channel proteins

1-Gradients-Frog in freshwater-Fish in ocean

-Frogs vs. Lizards, Pelvic Patch etc.

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Obligatory Osmotic Exchanges

4-Feeding, Metabolism, Excretion-metabolic waste products

ammonia, urea, etc.-metabolic water (desert!)-ingestion of salts-kidneys, salt glands, gills (more later)

5-Respiration

-internalize respiratory surface-temporal countercurrent system

(dry and cool IN, becomes moist and warm; recover)(countercurrent blood flow also)

-temperature regulation vs. water conservation-ectotherm vs. endotherm (in deserts)

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Osmoregulation

-Water Breathing

1. Fresh

Blood osmolarity 200-300 mosm/LWater ~ 50 mosm/L

- hyperosmotic animals, danger of swelling, losing salts- get their water across skin- dilute urine- active uptake of salts across epithelium- fish gills, frog skin, etc.

Ambystoma tigrinum

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Osmoregulation

-Water Breathing

2. Salt

Most marine vertebrates hypo-osmotic (e.g., teleost or bony fishes)

- danger of losing water, gaining too many salts- drink saltwater- excess salts actively secreted (gills, kidneys)- chloride cells for salt secretion

(Pelis et al. paper)

(~1,000 mosm/L)

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Osmoregulation

-Air Breathing

Have to lose water to allow gas exchange

- Marine reptiles and marine birds can drink seawater and secrete salts in high [ ]

- SALT GLANDS

- Mammals rely on kidney

(14-8)

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Osmoregulation

-Air Breathing Desert Mammals

Behavior and Physiology

Kangaroo Rat-Reduce Activity-Remain in Cool Burrow-Highly concentrated urine-Very dry feces (rectal absorption)-Metabolic water

(Eckert 14-9)

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Excretion of Nitrogeneous waste-When amino acids catabolized, amino group (-NH2) is released (deamination)-If not reused, need to excrete because toxic

1-ammonia (most toxic, requires lots water)‘ammonotelic’ (NH3)

2-urea (need 10% of water of NH3, but costs ATP)‘ureotelic’ (2N)

3-uric acid (white pasty substance, low solubility, need 1% water as NH3) ‘uricotelic’ (4N)

-Three main ways to dispose:

-Disposal depends on water availability

22Knut Schmidt_Nielsen 1997

Excretion of Nitrogeneous waste

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23Knut Schmidt_Nielsen 1997

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Excretion of Nitrogeneous waste

-ammonia converted to non-toxic glutamine in the body for transport

-ammonia toxic because -increases pH, -competes with K+ for ion transport, -alters synaptic transmission

(14-31)

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Osmoregulatory MechanismsApical surface (faces lumen and outside world)Basal surface (faces body and extracellular fluid)

- Active movement of ions/salts requires ATP- Movement of water follows movement of ions/salts

(14-11)

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Gradients established and used…to move ions, water

(Eckert 14-12)

active

passive

Mammalian Kidney

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Fish Gills Chloride cells involved in osmoregulation-(recall Pelis et al. paper on smolting)-lots of mitochondria to power ATPases-mechanism similar in nasal glands (birdsand reptiles), and shark rectal gland

(14-14)

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Kidney Functions:

-Osmoregulation-Blood volume regulation-Maintain proper ion concentrations-Dispose of metabolic waste products-pH regulation (at ~ 7.4)-Dispose of toxins and foreign substances

How does the kidney accomplish this?

(Eckert 14-17)

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(Eckert 14-17)Mammalian Kidney

-Paired-1% body mass-20% blood flow

-from ureter to urinary bladder(smooth muscle, sphincter, inhibition)

-out via urethra during micturition

-urine contains:watermetabolic byproducts (e.g., urea)excess salts etc.

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(Eckert 14-17)

Mammalian Kidney Anatomy

FUNCTIONAL UNIT(~ 1 million)

Urine

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-numerous nephronsempty into collecting duct

-collecting ducts empty into renal pelvis

1 -Proximal tubule2 -Loop of Henle

-descending-ascending

3 -Distal tubule

Nephron Anatomy

32Knut Schmidt_Nielsen 1997

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Nephron Anatomy

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33Knut Schmidt_Nielsen 1997

Vasa recta

Countercurrent exchange

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(Eckert 14-21)

1. FILTRATIONblood --> filtrate

2. REABSORPTIONfiltrate --> blood

3. SECRETIONblood --> filtrate

All 3 involved in finalUrine Composition

Kidney Processes- overview

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35Knut Schmidt_Nielsen 1997

Filtration plus secretionU/PMosm = x1000

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Dipodomys

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(14-20)

Sympathetic innervation tends to constrict

Humans:125 ml/min

or180 L/day

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Filtration:

Bowman’s capsule3 layers1. Glomerular endothelial cells

-100x leakier than other capillary walls2. Basement membrane

-negatively charged glycoproteins-repel plasma proteins by charge

3. Epithelial cells-podocytes create slits

Glomerular Filtration Rate (GFR)Humans: 125 ml/min or 180 L/day (60x plasma vol.)

Filtrate = protein-free and cell-free plasma

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Bowman’s capsule

(Eckert 14-23)

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(Eckert 14-22)

proteins and larger molecules remain

About 20% of the plasma and solutes that enter glomerulus end up in BC

Bowman’s capsule

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(Eckert 14-22)

1. Starvation Implications?

2. Kidney Stone Implications?

Bowman’s capsule