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Water Balance in Living Organisms. Water balance and blood pressure. Osmoregulation is the maintenance of internal salt and water concentrations in internal fluids despite different concentrations in the external environment Addition of water in the bloodstream = increased blood pressure - PowerPoint PPT Presentation
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Water Balance in Living Organisms
Water balance and blood pressureOsmoregulation is the maintenance of
internal salt and water concentrations in internal fluids despite different concentrations in the external environment
Addition of water in the bloodstream = increased blood pressure
Less water in the bloodstream = decreased blood pressure
KidneysOrgans for water balance control in
vertebrates
Eliminate nitrogenous waste
Kidneys are the blood’s filtration system
Vital for maintaining homeostasis and without kidneys we would only survive a few days
Glomerulus
Bowman’s capsule
Loop of Henle
Function of nephronsEach kidney contains approx 1 million
nephrons!
Maintain pH, ion and water balance by excreting excess ions, water, vitamins and hormones in the form of urine
Use active transport and passive transport
Antidiuretic Hormone (ADH)Vasopression is an antidiuretic produced by
neurosecretory cells in the hypothalamus
Secreted when osmoreceptors in the hypothalamus detect a rise in blood solutes (and therefore a decrease in water concentration)
Vasopression initiates a feeling of thirst and increases the permeability of the distal tubules in the kidney which helps to re-absorb water into the bloostream
ReninBlood volume decreases with dehydration
Pressure sensitive cells detect this this triggers the secretion of renin
Renin initiates a chemical reaction that releases aldosterone from the adrenal glands
Aldosterone acts on the distal tubules of the nephrons to actively re-absorb sodium ions and increase blood pressure
Nitrogenous waste
Water balance in AmoebaSingled celled organism, relatively simple to
maintain water balance
Live in aqueous environment with higher concentration of water outside the cell than inside
Water permeates the cell membrane via osmosis
Contractile vacuoles accumulate and expel the excess water
Waste products are diffused across the membrane
Water balance in fishFreshwater fish Marine (saltwater) fishTissues hypertonic to surroundings
Tissues hypotonic to surroundings
Concentration gradient results in a loss of salts and an uptake of water
Concentration gradient results in a loss of water and an uptake of salts
Fish must counter these changes to maintain homeostasis
Fish must counter these changes to maintain homeostasis
1. Does not drink 1. Drinks sea water
2. Kidney contains glomeruli and secretes copious amounts of very dilute urine. Tubules actively re-absorb NaCl
2. Minimal urine produced. Kidneys lack glomeruli. Tubules actively secrete MgSO4
3. Gill membranes permeable to water
3. Gill membranes are relatively impermeable to water
4. Gills actively absorb ions. Some ammonia leaves gills at the same time
4. Gills actively secrete sodium from chloride cells; chloride ions follow
Marine
Fresh water
Water balance in sea birdsWater, water everywhere and not a drop to
drink
Salt glands above the eye excrete a salt solution twice the concentration of sea water out the birds noseBirds with high salt diets have larger salt
glands
Excrete nitrogenous waste a uric acid
Water balance in reptilesAquatic reptiles
Turtles, crocodiles, alligators etcLots of water, nitrogenous waste is ammonia or
urea
Terrestrial reptilesLizards, snakes, goannas
Need to conserve water
Large number of kidney tubulesMore are active when hydrated and less when
dehydrated
Highly convoluted coprodaeum (region between rectum and cloacal opening) to re-absorb water
Can also have salt glands to excrete excess salts
Water balance in amphibiansFrogs, toads etc
Permeable skin allows diffusion of water and salts
Produce large quatities of dilute urine and ammonia
Actively transport Na and Cl across skin into the body
Biozone
Read page 261 “Managing fluid balance on land” and complete the questions of page 262.
Due: Monday 5 September