Lecture 5-3notes

Lecture 5-3notes - Summary of problems • ...

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Unformatted text preview: Summary of problems •  Freshwater Mechanisms for maintaining salt/ water homeostasis 10/1 RegulaBon strategies: marine 1 1.  Osmoconforming and ionoconforming –  Tends to gain water –  Tends to lose salt •  Marine •  Terrestrial –  Net loss/gain of salt depends on diet –  Tends to lose water –  Tends to lose water: Except osmoconformers –  Tends to gain salt RegulaBon strategies: marine 1 1.  Osmoconforming and ionoconforming •  Fig 13-4A; Sherwood Klandorf Yancy, Animal Physiology Salt in extracellular fluid is similar to that in seawater: ~1000 mM in total Fig 13-4A; Sherwood Klandorf Yancy, Animal Physiology 1 Ionoconformers RegulaBon strategies: marine 1 1.  Osmoconforming and ionoconforming •  •  Salt in extracellular fluid is similar to that in seawater: ~1000 mM in total Note on worksheet: If organism is iono ­ conformer, must be osmoconformer •  In ionoconformers, [salt]blood = [salt]SW •  In seawater, all solutes are salts, so osmorality of SW = Σ [salt]SW •  Osmorality of blood = Σ [salt]blood= Σ [salt]SW= osmorality of SW •  πblood = πSW so ionoconformers are osmoconformers Fig 13-4A; Sherwood Klandorf Yancy, Animal Physiology RegulaBon strategies: marine 1 1.  Osmoconforming and ionoconforming •  •  •  Fig 13-4A; Sherwood Klandorf Yancy, Animal Physiology Salt in extracellular fluid is similar to that in seawater Salt in cells much less Balance of osmoBc pressure due to organic osmolytes RegulaBon strategies: marine 1 2 1.  Osmoconforming and ionoconforming 2.  Osmoconforming and ionoregulaBng •  •  •  •  πECF = πseawater [salt]ECF < [salt]SW ConcentraBons of salt in ECF and cell similar, but kinds different (Na+ vs. K+) OsmoBc pressures made up with organic solutes Fig 13-4A; Sherwood Klandorf Yancy, Animal Physiology 2 RegulaBon strategies: marine 1 2 3 1.  Osmoconforming and ionoconforming 2.  Osmoconforming and ionoregulaBng 3.  Osmoregulator •  Not all organisms perfect conformers/regulators –  Perfect osmoregulator π of both ECF and cells is less than SW Fig 13-4A; Sherwood Klandorf Yancy, Animal Physiology RegulaBon strategies Not all organisms perfect conformers/regulators –  Perfect osmoregulator –  Perfect osmoconformer Fig 13-4b; Sherwood Klandorf Yancy, Animal Physiology RegulaBon strategies Fig 13-4b; Sherwood Klandorf Yancy, Animal Physiology RegulaBon strategies Not all organisms perfect conformers/regulators Some organisms regulate over a limited range, and slope may be >0 even within that range. Limits range of saliniBes organism can tolerate Fig 13-4b; Sherwood Klandorf Yancy, Animal Physiology 3 RegulaBon strategies •  Organisms with different strategies. •  Estuarine annelids: good osmo ­regulators Marine vertebrates: pre^y good osmo ­ regulators, body fluid ~300 mOsm Terrestrial animals •  Strong tendency to lose water to air •  SoluBons –  Limit loss •  Waterproof where possible (skin, etc.) •  Bury gas exchange surfaces (lungs, trachea) •  Minimize excretory volume, water content –  Replace: eat, drink Fig 13-4c; Sherwood Klandorf Yancy, Animal Physiology RegulaBon of fluids in animals •  How do animals separate two fluid regions of different composiBons? •  Using epithelia Epithelia DefiniBon: Bssues comprised of sheets of cells lining caviBes and separaBng fluids 4 Epithelia FuncBons Epithelia Examples Protect Compartmentalize Transport: control fluid composiBon Epithelia structure Figures in book Fig. 1 ­2 Fig. 2 ­33 Fig. 12 ­16,  ­17,  ­26 Fig. 13 ­21,  ­22 Fig. 14 ­22,  ­23,  ­24 Gills: external medium blood Gut walls: gut contents blood Secretory gland: gland content blood Nephron tubule: urine blood Epithelia structure Sides of Bssue mucosa Blood side: serosa (serum) Lumen/outside: mucosa (mucous) serosa 5 Epithelia structure mucosa Sides of cell Epithelia structure Apical surface Apical Brush border Faces mucosa Has brush border Individual projecBons call microvilli Increases surface area microvillus Apical Basal Faces serosa ProperBes similar to lateral membrane Combine: basolateral Has Na/K ATPase serosa basal surface Epithelia structure apical surface mucosa lateral serosa Epithelia structure Parts of cell apical surface mucosa Sides of cell Apical membrane Basolateral membrane Tight juncBon Parts of cell mucosa Tight juncBon SelecBve permeability Controls trans ­epithelial movement by paracellular pathway tight junction 2 K+ 2 K+ ADP serosa ADP basal surface 3 Na+ serosa 3 Na+ 6 Epithelia structure Tight juncBon mucosa Epithelia funcBon Determined by acBons of Controls trans ­epithelial movement by paracellular pathway Compare to transcellular pathway: controlled by apical and basolateral membranes mucosa Apical membrane Basolateral membrane Tight juncBon 2 K+ 2 K+ ADP serosa ADP serosa 3 Na+ Epithelia funcBon mucosa Types Epithelia funcBon AbsorpBve AbsorpBve 3 Na+ Na + mucosa Apical membrane has high Na+ influx Moves substrate from mucosa to serosa Absorb into blood Na + 2 K+ 2 K+ ADP serosa 3 Na+ ADP serosa 3 Na+ 7 Na+ absorbing Apical membrane has high Na+ influx Na+ absorbing Na + mucosa Na+ channels: High PNa Na+ ­symport systems Apical membrane has high Na+ influx (passive) Basolateral membrane has high Na+ efflux (acBve) Result: transcellular Na+ absorpBon (acBve) Na + Basolateral membrane has high Na+ efflux 2 K+ Via Na/K ATPase Na + 2 K+ ADP serosa ADP serosa 3 Na+ Na+ absorbing 3 Na+ Na+ absorbing Cl- Na + Chloride accompanies across tight junction: passively, paracellularly mucosa 2 K+ Na+ absorbing epithelium may be “tight” or “leaky”. • Tight: water does not follow NaCl across epithelium. • Cells have low Pw • Tight junction has low Pw 2 K+ 3 Na+ Na + mucosa Na + Cl- ADP Cl- Na + Na + mucosa ADP Na + serosa Cl- 3 Na+ Na + serosa 8 Tight Na+ absorbing Cl- Na + Freshwater fish mucosa Important when NaCl is to be absorbed, but not water Examples • Freshwater animals • Frog skin • Freshwater fish gills Fig. 13-11 Sherwood Klandorf and Yancey •  Tight Na+ absorbing funcBon in fish gills •  Chloride cells responsible: secretory cells embedded in gas exchange epithelium 2 K+ ADP 3 Na+ Cl- Na + serosa Tight Na+ absorbing Cl- Na + Important when NaCl is to be absorbed, but not water Leaky Na+ absorbing mucosa Examples • Freshwater animals • Frog skin • Freshwater fish gills • Ascending limb of loop of Henle in nephron (kidney) 2 K+ High Pw: Water follows osmotic gradient para- cellularly Because Pw is high, water follows salt rapidly, and difference build up in osmotic gradient is not measurable Isosmotic water flow 3 Na+ Low π 2 K+ ADP Cl- mucosa Na + H2O Cl- ADP Na + serosa Cl- 3 Na+ Na + serosa High π 9 Epithelia funcBon Secretory epithelia mucosa Types Basolateral membrane AbsorpBve: goes from M ­>S Na+: Tight epithelium: salts only absorbed Na+: Leaky epithelium: absorbs salts + water Secretory: goes from S ­>M 2 K+ mucosa Na/K ATPase Na/Cl symport or Na/K/Cl symport: AcBve Cl ­ influx Apical membrane High PCl mediates passive efflux of Cl ­ Na+ Cl- 2 K+ ADP serosa serosa 3 Na+ Secretory epithelia Basolateral membrane AcBve Cl ­ influx Apical membrane Passive Cl ­ efflux Net result AcBve transcellular S ­>M flux of Cl ­ mucosa Na+ Cl- serosa 3 Na+ Secretory epithelia Cl- Sodium follows passively, paracellularly 2 K+ 3 Na+ Na+ Na+ Cl- Cl- mucosa 2 K+ 3 Na+ serosa 10 Secretory epithelia Tight juncBon Pw low: Water does not follow (Bght epithe ­ lium) Pw high: Water follows isosmoBcally (leaky epithelium) Na+ Cl- Na+ Cl- H2O serosa Secretory epithelia Examples Na+ Examples Leaky epithelia primarily funcBon to secrete fluid Exocrine glands (note: mucosa is interior of gland) Sweat glands 2 K+ 3 Na+ Na+ Secretory epithelia mucosa Cl- H2O mucosa Na+ Cl- 2 K+ 3 Na+ serosa Salt secreBng glands Cl- mucosa Leaky epithelia Exocrine glands Sweat glands Tight epithelia: Salt secreBng glands (why marine vertebrates can drink seawater) Fig. 13-9a Sherwood Klandorf and Yancey Na+ Cl- •  Rectal gland releases content at hind ­most end of gut •  Salt excreted with feces 2 K+ 3 Na+ serosa 11 Salt secreBng glands Salt secreBng glands mucosa serosa Fig. 13-9b Sherwood Klandorf and Yancey •  Salt secreted from gills •  Again, chloride cells, single cells in gas exchange epithelium •  SecreBng, not absorbing NaCl Fig. 13-10 Sherwood Klandorf and Yancey Salt secreBng glands Salt secreBng glands Fig. 13-9c Sherwood Klandorf and Yancey •  Salt ­secreBng gland in head •  Saline fluid emerges from opening near eye –  “Crocodile tears” –  Also in terrestrial repBles, birds with high salt diet (sea gulls) •  Na/K ATPase on basal membrane •  Na/K/Cl symport on basal membrane •  Passive Cl leak from apical membrane •  Paracellular Na leak through Bght juncBon Fig. 13-9d Sherwood Klandorf and Yancey •  Mammals have no salt secreBng glands •  Do not drink, so do not exacerbate salt uptake: but how do they cope with water loss? 12 Salt secreBng glands Fig. 13-9d Sherwood Klandorf and Yancey •  Mammals have no salt secreBng glands •  Do not drink, so do not exacerbate salt uptake •  Hypertonic urine (πurine>πblood) –  Unique to birds and mammals –  Excretes more salt –  Excretes less water 13 ...
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This note was uploaded on 09/16/2011 for the course BIO 203 taught by Professor Loretz during the Fall '09 term at SUNY Buffalo.

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