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Ionic and Osmotic Balance

Ionic and Osmotic Balance . Ion & Water Balance. Kidneys are main organs of ion & water balance Gills, skin, digestive mucosa all help with ion and water balance. Osmotic Regulation. Primarily due to solute movement Animals do not actively pump water. Ionic Regulation.

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Ionic and Osmotic Balance

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  1. Ionic and Osmotic Balance

  2. Ion & Water Balance • Kidneys are main organs of ion & water balance • Gills, skin, digestive mucosa all help with ion and water balance

  3. Osmotic Regulation • Primarily due to solute movement • Animals do not actively pump water

  4. Ionic Regulation • Control of ionic composition of body fluids

  5. Nitrogen Excretion • Nitrogen waste from protein catabolism • Forms of nitrogen waste include ammonia, uric acid, urea

  6. Most Marine Animals • Maintain ionic balance by expelling ions (especially salt) against ionic gradient • Maintain osmotic balance by obtaining water against osmotic gradient

  7. Most Fresh Water Animals • Maintain ionic balance by acquiring ions from ion-poor water • Maintain osmotic balance by expelling excess water against osmotic gradient

  8. Terrestrial Animals • Constantly challenged with dehydration

  9. Ionoconformers • Internal conditions are similar to external conditions even if external conditions change • ECF resembles seawater in terms of major cations and anions • See examples in blue

  10. Seawater Jelly Fish Starfish • Osmolarity(mosM) 1000 • Na+ (mM) 460 454 428 • K+ (mM) 10 10 10 • Ca++(mM) 10 10 12 • Mg++(mM) 53 51 49 • Cl- (mM) 540 554 487 • SO4= (mM) 27 15 27

  11. Ionoregulators • Controls the internal conditions in their ECF by using ion absorption & excretion • Shark, freshwater animals • Regulated ECF eases the burden on individual cells to regulate ions

  12. Seawater Shark Flounder Goldfish • Osmolarity(mosM) 1000 1075 337 293 • Na+ (mM) 460 269 180 142 • K+ (mM) 10 4 4 2 • Ca++(mM) 10 3 3 6 • Mg++(mM) 53 1 1 3 • Cl- (mM) 540 258 160 107 • SO4= (mM) 27 1 .2

  13. Osmoconformer • Internal osmolarity is close to that of the external environment even if environment changes • Marine invertebrates, primitive vertebrates

  14. Seawater Shark Flounder Goldfish • Osmolarity(mosM) 1000 1075 337 293 • Na+ (mM) 460 269 180 142 • K+ (mM) 10 4 4 2 • Ca++(mM) 10 3 3 6 • Mg++(mM) 53 1 1 3 • Cl- (mM) 540 258 160 107 • SO4= (mM) 27 1 .2

  15. Osmoregulator • Internal osmolarity is maintained within a narrow range regardless of environment • Most marine vertebrates • Freshwater vertebrates • Freshwater invertebrates

  16. Seawater SharkFlounderGoldfish • Osmolarity(mosM) 1000 1075 337 293 • Na+ (mM) 460 269 180 142 • K+ (mM) 10 4 4 2 • Ca++(mM) 10 3 3 6 • Mg++(mM) 53 1 1 3 • Cl- (mM) 540 258 160 107 • SO4= (mM) 27 1 .2

  17. ECF of most marine invertebrates is similar from seawater. • ECF of most marine vertebrates is different from seawater. • ECF of most marine vertebrates is similar to mammals.

  18. ICF of most animals is low in Na+, Cl- but high in K+, phosphates and proteins.

  19. Osmoregulatory mechanisms • Frog in fresh water (hypo osmotic environment) not only must eliminate excess water but also retain ions that tend to leak though the skin. • Since animals live in a wide range of environments many different osmoregulatorymechanisms have evolved.

  20. Water Sources • Aquatic environment • Diet • Metabolism

  21. Solutes – Inorganic & Organic • RVI – Regulatory Volume Increase: importing ions resulting in influx of water • Na+-K+-2Cl- cotransporter

  22. Regulatory Volume Decrease • RVD • K+ channels; Cl- channels (separate or as cotransporters) & these exit cell • Na+/Ca2+ exchanger followed by Ca2+ ATPase to export calcium • Na+/K+ ATPase pump • Water follows

  23. Osmotic and Ionic Differences • Epithelia surrounding the body maintains both osmotic and ionic differences between the ECF and the external environment . • Aquaporins are pores in epithelium for water passage • Solutes move by transcellular and paracellular transport

  24. Integument (epithelium plus underlying tissue). • Permeability varies among animals. • Insects: waxy impermeable cuticle. • Amphibians skins: mucus, permeable. Water and ions move by diffusion. Loss of ions compensated by active transport. • Fish gills: active transport of ions. • Reptiles, birds and mammals: relatively impermeable keratinized skins. Perspiration can lead to substantial water loss.

  25. Gills • Transports ions in or out of water depending on salinity of water

  26. Digestive mucosa • Solutes move across digestive mucosa • Water moves across digestive mucosa

  27. Salt Glands • Birds and reptiles • Excretes Na+ and Cl- • Functions as countercurrent multiplier systems

  28. Rectal Glands • Sharks • Excrete salt

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