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21 Cards in this Set
- Front
- Back
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Electrolytes
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Salts dissociate in solution into charged ions
Electrolyte balance important Imbalance can alter membrane potential or disrupt cellular activities |
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Electrolytes (2)
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Water moves between adjacent body compartments by osmosis down an osmotic gradient
Changes in salt concentration in one compartment will lead to changes in fluid distribution between compartments Shrinking or swelling cells can rupture plasma membranes leading to cell death |
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Obligatory exchanges
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Many vital processes have the potential to disturb salt and water balance
Obligatory exchanges are required as part of respiration or elimination of wastes |
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Nitrogenous wastes
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Product of protein and nucleic acid degradation
Toxic at high concentrations 3 forms Ammonia and ammonium ions Urea Uric acid |
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Freshwater fish
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Gain water and lose salt when ventilating gills
Kidneys produce copious dilute urine Specialized gill epithelial cells transport Na+ and Cl- from water into fish’s capillaries |
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Saltwater fish
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Gain salts and lose water across gills
Produce very little urine Drink seawater to replace water lost Expend energy to transport excess salt out of body through gill epithelial cells |
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Exchanges during ingestion
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Food contains minerals and water
Unusable parts of food are excreted as solid waste with accompanying water and salt loss Marine reptiles and birds ingest seawater when consuming prey or drinking – salt glands used to excrete excess salt |
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Salt glands
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Contain a network of secretory tubules that actively transport NaCl from the interstitial fluid into the tubule lumen
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Body temperature
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Endotherms use body water to cool off
Sweating and panting use the evaporation of water to draw heat out of the body Sweat is hypoosmotic to blood Fluid left behind in body has lower volume and higher salt concentration |
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Metabolism
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Water is generated as a by-product of ATP production – “metabolic water”
Some animals rely on this for all or nearly all of their water requirements In other animals, this water is excess that must be eliminated Excretion or retention of metabolic water can be considered a type of obligatory exchange |
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Regulate or conform
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Osmoregulators maintain constant internal salt concentrations and osmolarities
Drink or excrete as needed to maintain 300 mosm/L All terrestrial animals, freshwater animals, and many marine animals Requires considerable expenditure of energy |
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Osmoconformers match osmolarity of blood and other fluids to seawater at 1000 mosm/L
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Most marine invertebrates and some vertebrates
Less tendency to gain or lose water across skin or gills Expend less energy to compensate for water gain Generally limited to marine environment |
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Filtration
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An organ acts like a filter to remove water and small solutes from blood while leaving behind blood cells and large solutes
Produces filtrate |
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Reabsorption
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Material in filtrate recaptured and returned to blood
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Secretion
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Supplements solutes removed by filtration
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Protonephridia
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Simplest filtration mechanism in invertebrates
Flatworms Series of branching tubules filters fluids from body cavity using beating of ciliated cells (flame cells) |
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Protonephridia (2)
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Solutes reabsorped
Excess water and some wastes emptied through openings in body wall called nephridiopores Osmoregulatory – nitrogenous wastes diffuse out of body |
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Metanephridial system
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Annelids
Pairs located in each body segment Tubular network beginning in funnel-like structure called nephrostome Collect coelomic fluid containing nitrogenous wastes Na+, Cl- and others reabsorbed along tubule Nitrogenous wastes excreted through nephridiopores in body wall |
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Malpighian tubules
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Insects use secretion and not filtration
Cells lining tubules actively transport potassium ions and uric acid from hemolymph into lumen Creates osmotic gradient drawing water and solutes into tubule Moves to hindgut where water and solutes reabsorbed Nitrogenous wastes and others excreted together with feces through anus |
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Kidney
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Vertebrates
Specialized tubules composed of epithelial cells Participate in both salt and water homeostasis Nitrogenous waste elimination Most vertebrate kidneys are filtration kidneys Filtration controlled by mechanical forces |
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Nephron
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Functional unit of the kidney
As many as several million in each kidney Consists of Renal corpuscle forms filtrate Tubule performs secretion and reabsorption Tubule empties into collecting duct |
