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CONTROL OF THE INTERNAL ENVIRONMENT Chapter 25 THERMOREGULATION Maintenance of an internal temperature Life processes are temperature sensitive Stable internal temperature despite external fluctuations Endotherms use their metabolism Some reptiles, fish, and insects too Ectotherms gain heat from external sources Not mutually exclusive HEAT EXCHANGE Conduction: molecules between 2 objects in direct contact Higher to lower temperature movement Convection: movement of air or liquid past an object Radiation: electromagnetic waves between 2 objects not in direct contact Evaporation: surface of a liquid losing molecules as a gas ADAPTATIONS FOR THERMOREGULATION Metabolic heat Hormonal boost or moving around to contract skeletal muscles, i.e shivering Insulation Hair, fur and feathers rise to trap insulating layer of air, goose bumps are vestigial remnant Blubber in aquatic birds and mammals Circulatory adaptations Change blood flow by constricting blood vessels to surfaces to conserve heat, dilation to dissipate Countercurrent heat exchange: adjacent vessels flow opposite directions Evaporative cooling Standing on ice, cold water across gills, and muscles Sweating and panting expose moisture to be removed with heat Behavioral response Migration, basking in sun when cold and damp areas when hot, bathing, and layered clothing OSMOREGULATION Balancing uptake and loss of water and solutes Osmoconformers: no net gain or loss of water Animal cells: net uptake = ? Net loss = ? Water follows solutes by osmosis Marine invertebrates have body fluids of similar [solute] as seawater Osmoregulators: necessary to regulate to prevent changes Freshwater fish have higher [solute] than environment Saltwater fish have lower [solute] than environment H2O gained and salt lost = doesn’t drink H20, ions from food, and lots of dilute urine H2O lost and salt gained = drinks salt H2O with salt out gills and little concentrated urine Land animals obtain H2O from food and drink while losing water through evaporation and excretion Exoskeleton, dead skin layers, egg shells, and amnitotic sac to prevent dehydration DISPOSAL OF WASTES Metabolism produces toxic nitrogenous wastes that are removed by excretion Form of waste depends on habitat and evolution Ammonia too toxic to store, but diffuses in water Urea less toxic so can be stored, but costs energy and H2O loss to remove Uric acid insoluble in H2O so is semisolid Costs more energy, but conserves H2O URINARY SYSTEM Forms and excretes urine while regulating water and ion concentrations in body fluids Kidneys filter blood to extract filtrate which contains H2O, urea, glucose, AA’s, ions, and vitamins Filtrate is processed so valuable solutes not lost in urine Blood enters kidney through the renal arteries to be filtered and leaves via the renal veins What is the urine pathway from kidneys to outside? THE KIDNEYS Consist of renal cortex (outer) and renal medulla (inner) Nephrons are the functional units Bowman’s capsule encloses the glomerulus which filters the blood Start and end in cortex, part in medulla Nephron tubule has 3 parts Drains to collecting duct to join filtrate from other nephrons Capillary system in Bowman’s capsule and around tubule system URINARY SYSTEM PROCESSING Filtration Reabsorption Filtrate returns valuable solutes to blood (tubule capillaries) Secretion H2O and small molecules through capillary tube from glomerulus to nephron tubule Excess ions, drugs, and toxic substances from blood transported into filtrate (tubule capillaries) Excretion Urine from kidneys to outside BLOOD FILTRATE TO URINE NaCl enters interstitial fluid, bringing H2O with Excess H+ secreted and HCO3reabsorbed to maintain blood pH Toxins from liver into tubule system Loop of Henle facilitates H2O reclaimation ADH sets amount of H2O reabsorbtion Lots of H2O dilutes solutes so ADH down = less H2O retained Alcohol inhibits ADH release = excess H2O loss
