Osmotic regulation part 1
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The document discusses the principles of osmoregulation and water balance in organisms, emphasizing the importance of maintaining consistent body fluid composition in various environments. It covers different types of osmotic organisms, their adaptations to saline conditions, and cellular mechanisms that regulate ion concentrations. Additionally, it addresses the challenges faced by terrestrial and aquatic vertebrates regarding water conservation and the specific adaptations for dealing with dehydration and salt intake.
Osmotic regulation part 1
- 1. WATER AND OSMOTIC REGULATION Dr. Nagabhushan CM Assistant Professor, Dept. Of Studies in Zoology, Vijayanagara SriKrishnadevaraya University, Ballari, Karnataka 583 104 nagabhushancm@vskub.ac.in 1
- 2. What ? • ORGANISMS are the aqueous solutions contained within a membrane… ? • Both the volume of the organism and the concentration of solutes should be maintained within narrow limits, • For optimal functioning animal requires TO MAINTAIN its body fluids with a relatively constant composition. • The problems of keeping water and solute concentrations constant vary with the environment. 2
- 3. terms • Euryhaline organisms • Stenohaline organisms • Isosmotic organisms (Most marine invertebrates have body fluids with the same osmotic pressure as the sea water) • Hyperosmotic • Hyposmotic • Osmo-Conformers • Osmo-regulators • The concentration of dissolved substances is expressed in molarity (moles per liter solution) ex. A sol of 0.5 moles per liter is equal to 500 mmol per liter (millimole). 3
- 4. • The osmotic concentration of a solution can be expressed as the osmolarity (osmoles per liter). • The osmolarity of a solution of a nonelectrolyte (e.g., sucrose or urea) equals its molar concentration. • The osmolarity of an electrolyte (e.g., sodium chloride, which in solution dissociates into Na+ and CI -- ) has a higher osmotic concentration than is expressed by its molarity. • Isotonic v/s isosmotic are different (ex: blood in saline and urea solution). 4
- 5. osmoconformers • As a rule marine invertebrates are osmo-conformers, this does not mean that their body fluids have the same solute composition as sea water. On the contrary, there are characteristic differences that the animals must maintain, and this requires extensive regulation of ionic concentrations. • Must have a mechanism for eliminating some ions while maintaining others at a higher level than that in the water. Ex.the kidney. 5
- 6. • Dialysis (Donnan’s effect of proteins) where salts and ions can pass through the cellophane whereas the proteins cannot. • Echinoderms show no significant regulation of any ions. • Aurelia regulates only SULPHATE by keeping its level considerably below the sea water to maintain BUOYANCY • Fast moving arthropods have LOW LEVELS OF Mg whereas slow moving arthropods have HIGH LEVELS. (Mg can act as an anaesthetic) 6
- 7. Intracellular conc and vol regulation • The concentrations of ions inside the cells are usually very different from those outside; • Ex. Sodium and chloride concentrations are usually low inside the cells and high outside, and potassium is usually high inside and low outside. • However, the cells are isosmotic with the surrounding tissue fluid and blood, although the concentrations of individual solutes differ. 7
- 8. Thanks to aminoacids for constant cell volumes • It is now well established that intracellular concentration of free amino acids is an important factor in the control of cell volume in salinity-stressed environments. • As the salinity of water fluctuates, the amino acids in the cells increase or decrease so that the cells remain isotonic with the surroundings. • DECREASE in AA concentration is achieved by the synthesis of PROTEIN & INCREASE in AA is achieved by the degradation of proteins. 8
- 9. Animals in FW and BW • Marine animals INTO brackish water === SURVIVE • OSMOCONFORMERS have same osmotic concentration as the dilute medium • OSMOREGULATORS resist the dilution by remaining hyper-osmotic. • Marine animals INTO brackish water === SURVIVAL OF PASSIVE OSMOCONFORMERS OR ACTIVE OSMOREGULATORS 9
- 10. MECHANISM OF OSMOREGULATION • When an animal is hyperosmotic to the surrounding medium, it encounters two physiological problems: • (1) water ENTERS into the animal (because of higher inside concentration) • (2) solutes tend to be LOST (because the inside concentration is higher and because the water that enters must be excreted and carries some solutes with it.) • anal gills / gills / appendages maintain the ion uptake by ACTIVE TRANSPORT is evident by the increase in the OXYGEN UPTAKE. 10
- 11. AQUATIC VERTEBRATES 11 • The marine representatives fall into two distinct groups: • 1. those whose osmotic concentrations are the same as or slightly above sea water (hagfish, elasmobranchs, Latimeria, etc) • 2. those whose osmotic concentrations are about one-third that of sea water (lamprey, teleosts). • The former group has no major problem of water balance, for if the inside and outside concentrations are equal, there is no osmotic water flow. • In contrast, those who are hyposmotic live in constant danger of losing water to the osmotically more concentrated medium.
- 12. cyclostomes • Lampreys live both in the sea and in fresh water. • have osmotic concentrations about one-quarter to one-third the concentration of sea water. • Hagfish are strictly marine and stenohaline. • Hagfish are the only true vertebrates whose body fluids have salt concentrations similar to that of sea water. 12
- 13. elasmobranchs • sharks and rays are almost without exception marine. • They have solved the osmotic problem of life in the sea in an interesting way. • They maintain salt concentrations in their body fluids at one-third the level in sea water, but they still maintain osmotic equilibrium. • This is achieved by adding to the body fluids large amounts of organic compounds, primarily urea, & TMAO so that the total osmotic concentration of their blood equals or slightly exceeds that of sea water. 13
- 14. teleosts 14
- 15. The terrestrial environment • The greatest physiological advantage of terrestrial life is the easy access to oxygen; • greatest physiological threat to life on land is the danger of dehydration • the rate of diffusion of water vapor into air increases with increasing temperature and the diffusion rate increases with decreasing barometric pressure 15
- 16. Moist skinned animals • Vapor – limited system (moist animals) • Membrane-limited systems (insects with cuticle) • Earthworms behaviour: hydro-permeable skin; dehydrates and dies in dry soil / salty soil. • Amphibians : live near the water/humid where evaporation is LOW. Some aestivate in burrows & restore water during rainfall. • Snails: shell as barrier prevents evaporation. 16
- 17. arthropods • Bury during DAY AND COME OUT DURING NIGHT • CRABS take up water from damp soil / substratum • Woodlice live in moist decaying plant material. • WAXY layer on the CUTICLE reduces evaporation. • WATER BALANCE: 17 WATER LOSS BY WATER GAIN BY EVAPORATION FROM BODY SURFACE, DRINKING RESPIRATORY ORGANS UPTAKE OF WATER BY BODY SURFACE FAECES UPTAKE OF WATER FROM MOIST AIR URINE WATER IN FOOD OTHERS METABOLIC WATER
- 18. TERRESTRIAL VERTEBRATES • 4 ORDERS of REPTILES • Crocodiles associated with water • Snakes • Lizards well adapted to DRY habitats. • Tortoises • There is close correlation betw evaporation and habitat. • The drier the normal habitat, the lower the rate of evaporation. • In addition to water lost through evaporation, water is needed for URINE FORMATION (therefore uric acid is excreted). 18
- 19. TERRESTRIAL VERTEBRATES • BIRDS AND MAMMALS • Perspiration • Panting • Conservation of water/ using water from the metabolic oxidation/ economic use of water in urine/ reduction in respiratory evaporation. 19
- 20. MARINE air-breathing vertebrates • The excretion of excess salt, which the kidney is unable to handle, is carried out by glands in the head called salt- excreting glands or simply salt glands. • The salt glands produce a highly concentrated fluid that contains primarily sodium and chloride in concentrations substantially higher than in sea water. • The glands do not function continually, as the kidney does; they secrete only intermittently in response to a salt load 20
- 21. Man in wild ocean • Sea water is toxic to man and that a castaway at sea only hastens the dehydration processes if he drinks sea water. • The effect of drinking sea water on the water balance of a man and of a whale: 1. A whale can drink 1 liter of sea water and have a net gain of about one-third liter of pure water after the salts are excreted. 2.The kidney of man is less powerful; the maximum urine concentration is below that of sea water, and if he drinks 1 liter of sea water, he inevitably ends up with a net water loss of about one-third liter and is worse off than if he had not drunk at al. 21
- 22. Thus the organs of excretion are so important for the maintenance of the relative constant / steady state of internal concentration and water content of living organisms.. 22