Water Balance Flashcards Preview

Animal Physiology, Reproduction and developement > Water Balance > Flashcards

Flashcards in Water Balance Deck (22)
Loading flashcards...

Why do we need to regulate water content in the body?

The concentration of body fluids is usually different to that of the external environment


What happens if water uptake is less than water loss over time?

Not enough water, cells shrivel and die


What happens if water uptake is more than water loss over time?

Cells swell and eventually burst


What is osmosis?

Net movement of water across a selectively permeable membrane.


What is osmoregulation?

The process that balances the uptake and loss of water - under homeostatic control


What is passive movement?

Along a concentration gradient


What is active movement?

Against a concentration gradient


What influences the passive rate of movement?

Temperature, size of particles, electrical charge, concentration gradient


What is osmolarity?

measure of the osmotic pressure exerted by a solution across a perfect semi-permeable membrane compared to pure water


What is the calculation for osmolarity?

= (number of particles/molecules of solute) x (moles/litres)


How can we use osmolarity to compare two solutes?

When two solutes differ in osmolarity, one solution is hyperosmotic, with a greater concentration, and the other, with a lower concentration is hypo-osmotic


What does it mean if two solutions are iso-osmotic?

They have an equal osmolarity


What is tonicity?

The effect of a solution on cell volume, depends on concentration of non- penetrating solutes only


What are osmoconformers?

Iso-osmotic with the surroundings. All are marine animals. Because internal environment is same as external, there is no tendency to gain or lose water


What are osmoregulatory?

Osmolarity of body fluid regulated to within set range. Enables animals to live in environments that are uninhabitable for osmo-conformers, e.g. freshwater/terrestrial, or marine mammals to maintain different internal osmolarity to seawater.


What are limited osmoregulatory?

Have limited ability to regulate osmolarity of body fluid


Compared to the body fluids, what is the osmolarity difference in freshwater?

Freshwater is hypo-osmotic compared to the organism. Environment is high water concentration, low salt concentration


Compared to the body fluids, what is the osmolarity difference in seawater?

Seawater is hyper-osmotic compared to the organism. environment is low water concentration, high salt concentration


How do marine teleosts regulate water?

Are hypo-osmotic to the environment, salt is gained by diffusion and water is lost by osmosis. Small amounts of concentrated urine.


How do marine fish get rid of salt?

Na+/K+ ATPase pumps builds huge Na+ gradient within a chloride cell - Na is pumped out
Cl- transported using Na+ gradient (Cl-/Na+ symporters)
Cl- builds up and diffuses out
Na+ follows Cl- charge by sneaking through leaky tight cell junctions


How do freshwater teleosts regulate water?

Hyperosmotic to the environment. Salts are lost by diffusion, Salts and water gained in food, Water uptake by osmosis. Actively transport in salt, and produce large amounts of dilute urine


How do freshwater fish gills work?

Have lots of mitochondria and Na+/K+ ATPase
Cell cytoplasm very low in Na+ and Cl-, so salt diffuses in.
Apical membranes have ion pumps to pump ions IN
Cell junctions very tight (no ion leak), so no salt loss