Regulating Body Fluids Flashcards
What do intracellular and extracellular fluids contain?
- complex solutions consisting of solutes dissolved in a solvent (solvent being water)
- these solutes include ions such as Na+ and K+, as well as organic molecules such as glucose, fatty acids and lipids
What is osmolarity and what is its unit?
Osmotic concentration, aka concentration of all osmotically active solutes known as osmolytes. (E.g na+ and cl- are osmolytes of nacl). Unit is Osm/L
Is osmolar concentration always equal to molar concentration?
No for solutes that dissociate. E.g 1M NaCl has molar concentration of 1 and osmolar concentration of 2 Osm/L. 2 because dissociates into two ions Na+ and Cl-
What is tonicity? What three terms describe it?
Concentration of non-permeable solutes (cannot cross semi-permeable membrane).
Hypertonic, hypotonic and isotonic.
What is a hypotonic solution?
Extracellular fluid has lower osmolarity than fluid inside the cell. Therefore net movement of water into the cell. (Hypo means less than)
What is a hypertonic solution?
Extracellular fluid has higher osmolarity than fluid inside the cell, therefore net movement of water out of cell
What is an isotonic solution?
Extracellular fluid and fluid inside cell are equal in osmolarity
What important aspects of the extracellular environment (surrounding animal’s cells) are regulated?
Major ions such as Na+ and Cl-, organic solutes, gases including O2 and CO2, pH and temperature
What is homeostasis?
Constancy of extracellular environment
Why is body water and solutes regulated?
- in order to achieve homeostasis (constancy of extracellular environment)
- exact and relative concentrations of solutes in body fluid are critical for proper chemical functioning
What is the way in which an animal regulates osmotic concentration determined by?
Surrounding environment.
What is an osmoconformer?
Animal allows the osmotic concentration of their extracellular fluids to equal that of their external environment. E.g iso-osmotic to seawater
What kinds of animals are osmoconformers?
Marine invertebrates.
What characteristics of the marine environment enables marine invertebrates to osmoconform?
The constancy of the seawater environment (e.g osmotic concentration, ion concentration, pH, temperature, gases) means that marine invertebrates do not require homeostatic mechanisms to regulate these variables.
Do osmoconformers live in environments where salinity changes very little or fluctuates a lot? Why or why not? Are they therefore stenohaline or euryhaline?
- osmoconformers live in environments where salinity changes very little
- this is because they cannot cope with large changes in body salinity
- osmoconformers are therefore stenohaline
What type of homeostasis do osmoconformers use and how does it work? Is it active or passive?
- Equilibrium homeostasis
- constancy of extracellular environment is achieved passively by simply being in equilibrium with their environment
What does stenohaline mean and does it apply to osmoconformers or osmoregulators?
- an animal that relies on passive homeostasis and has little tolerance to change in external environment
What are the advantages and disadvantages of being an osmoconformer?
Benefit: conserve more energy to fuel other biochemical reactions or physiological processes as they do not need to use energy in regulating extracellular environment independently of external environment
Disadvantage: cannot easily control osmotic concentration if sudden extreme change occurs in environment
What is an osmoregulator?
An animal that regulates extracellular osmotic concentration independently of external environment.
What kinds of animals are osmoregulators?
Marine vertebrates, freshwater and terrestrial animals
Do osmoregulators live in environments where salinity changes very little or fluctuates a lot? Why or why not? Are they therefore stenohaline or euryhaline?
- live in environments where salinity changes a lot
- this is because they can cope with a wide range of salinities
- therefore euryhaline
In terms of water and solute balance, what problems are faced by marine osmoregulators? How are these solved?
- body fluid is HYPOTONIC to seawater (has lower tonicity and osmolarity than seawater)
- high loss of water from body as water moves from region of high water potential to region of low water potential
- LOSE water from body fluids to seawater via osmosis occurs across skin, gills if present, and in excretion of urea and faeces
- water is replaced by animal drinking lots of seawater
- problem is that seawater contains a lot of ions which enter the animal’s body passively via diffusion
- not enough water, too much salt!
- the influx of excess ions is counteracted by the animal releasing small amounts of concentrated urine and actively secreting ions either across gills, by kidneys or by salt glands
In terms of water and solute balance, what problems are faced by freshwater osmoregulators? How are these solved?
- body fluid is hypertonic to freshwater (body fluid has greater osmolarity and ion concentration than external environment)
- therefore water will ENTER body via osmosis as it moves from region of high water potential to region of low water potential
- lose solutes by passive diffusion
- problem is too much water, not enough salt
- this is counteracted by the animal producing lots of dilute urine to remove water
- animal will not drink water
- possess organs that actively retain salts (kidneys, gills)
How do gill epithelial cells help freshwater osmoregulators?
- pump Na+ and Cl- ions from water flowing over gills INTO blood
- therefore increase solute concentration of blood
How do gill epithelial cells help marine osmoregulators?
- pump Na+ and Cl- ions from water flowing over gills OUT OF blood into water
- therefore decrease solute concentration of blood
How does the kidney function differ between marine and freshwater osmoregulators?
Marine: kidney tries to concentrate urine as much as possible, produces very small amount of urine to prevent loss of water
Freshwater: kidney produces lots of dilute urine
How do salmon cope with life in both salt and freshwater?
Background: salmon are born in fresh water then migrate to ocean and spend years maturing at sea, then return to freshwater to breed
- kidneys as gills of salmon must therefore cope with both marine and freshwater conditions
- this is achieved via acclimatisation. Salmon need to spend several days in brackish water at river mouth (water that has slightly more salinity than freshwater) to ACCLIMATISE
- kidney function must change and Na+ and Cl- gill pumps must reverse direction.
In terms of water and solute balance, what problems are faced by terrestrial osmoregulators? How are these solved?
Background: obligate osmoregulator, few problems with ion concentration
- problem is not enough water in environment especially for desert animals
- water is also lost from animal via evaporation and in urine and faeces
Solutions:
- water is obtained from food including via metabolic water production (example: camels metabolise fat stored in humps, byproduct of this process is H2O)
- respiratory surfaces kept inside to prevent them from drying out
- some animals absorb water through skin and anus
- insulate skin with hair which can change microenvironment to allow water in or out)
- minimise water loss during waste excretion by concentrating urine
How do thorny devils cope with life in the desert?
possess special adaptations:
- specialised skin texture to capture dew and rainwater
- scales surrounded by tiny interconnected channels that attract water
- water is then funnelled into mouth
What product of the metabolism of protein must be excreted?
Nitrogen
What is the difference between excretion and elimination?
Excretion - via urine
Elimination - via faeces
What is the FIRST product of protein metabolism and how do aquatic animals deal with it?
- toxic ammonia NH3
Excreted by aquatic animals
What do terrestrial organisms do with toxic NH3? How does this differ between terrestrial species?
- convert toxic NH3 into non toxic form
Soluble urea in some invertebrates and mammals
Insoluble uric acid in reptiles and birds
Insoluble guanine in spiders and scorpions
What is the kidney and what is its main function?
- the kidney is the principle excretory organ of vertebrates
- its main function is to regulate the excretion of solutes and water
What do juxtamedullary nephrons allow mammals to do?
Concentrate their urine
What are the 4 key functions of a nephron?
- filtration of all blood plasma except RBC and large proteins which occurs in renal tubule
- reabsorption of ions (e.g sodium and chloride) and organic molecules(e.g glucose and vitamins) which re-enter blood
- secretion of some ions (e.g K+, NH4+, H+) from blood into renal tubule
- osmosis which controls amount of water in body (osmodilution and osmoconcentration)
How does osmoconcentration in the mammalian kidney work?
- juxtamedullary nephrons establish high osmotic concentration in the inner medulla
- thick ascending limb of loop of Henle actively pumps ions out of filtrate
- this causes water to move by osmosis out of the tubule which is then reabsorbed by the body
- countercurrent multiplication establishes concentration gradient outside ducts
- osmosis of H2O out of collecting duct and thin descending limb concentrates urine
Why is the loop of Henle especially long in desert dwelling animals?
- maintain as much water as possible before it gets converted into urine
What will the loop of Henle’s length be when H2O upkeep isn’t as important?
Will be shorter in length
