Water & Salt Physiology Flashcards
What are the urine composition and plasma composition ratios in the kidneys (U/P ratios)?
- Hyposmotic (U/P<1) urine less concentrated than blood (freshwater & most terrestrial animals)
- Isosmotic (U/P = 1) urine is the same concentration as the blood
- Hyperosmotic (U/P>1) = urine more concentrated than blood (mammals, birds & insects)
U/P ratios =
Ratio of urine composition (U) over plasma (P) composition –> Urine composition (150 mOsm) / plasma composition (300 mOsm)
Describe the aquatic environments ? (Open oceans)
- Uniform and stable
- Salinity = 3.36 g kg
- Osmotic pressure = 1000 mOsm
Describe the freshwater environments? (Lakes, rivers)
- Salinity < 0.5 g kg
- Uniform osmotic pressure = 0.5 - 0.15 mOsm
- Variations in ion concentrations from one body of freshwater to another (High Ca2+ = hard water
Low Ca2+ = soft water)
Describe the brackish water environments? (Estuaries - ocean + freshwater mixture)
- Highly variable in time and space
- Intermediate salinity = 0.5 - 30 g kg
- Osmotic pressure = 15 - 850 mOsm
Describe the terrestrial water environments?
- Water in gaseous state and free of salts
- Water vapor pressure
- Limit to water vapor pressure = saturation
- Point of saturation increases with temperature
- Warmer air contains more water vapor
- Evaporation increases in drier env.
- Water loss from evaporation is the biggest challenge for terrestrial env.
Describe the freshwater fish passive processes?
- Water gain to try & dilute their blood
- Salt water loss = ions move down concentration gradient
(Hyperosmotic - more concentrated than their environment)
What are the freshwater fish influenced by during passive processes?
- Osmotic and ionic gradients
- Permeability of animals outer body to water and ions
- Surface area across which exchange is occurring
How do freshwater fish regulate urine?
- Produce dilute urine in large volume
- Hyposmotic to the blood = U/P osmotic and ionic ratios <1
- Kidneys are regulatory = regulations all the time
What do the gills do in freshwater fish?
Actively uptake Na+ and Cl- into blood
Describe the marine fish passive processes?
- Water loss = water wants to move out to dilute sea water
- Salt gain = ions move in down concentration gradient
(Hyposmotic = less concentrated than their env.)
How do marine fish regulate urine?
Drink seawater and replace water lost by osmosis
- Salt balance is disrupted
- Excrete Mg2+ and SO2-4 (divalent ions) in urine at kidneys
- Actively uses ATP
What do the gills do in marine fish?
Actively excrete Na+ and Cl- (monovalent ions)
Actively uses ATP
Xeric =
Capable of living in dry, water-poor environments
- lipid layer to reduce water loss
- respiratory surfaces inside body
Humidic =
Restricted to humid, water-rich environments
- live underground, leaf litter, under logs/rocks
- can only reduce water loss by living in a humid environment
- high permeability (skin, exoskeleton)
Respiratory evaporative water loss =
Evaporation from breathing
- air is saturated when exhaled, but exhaled at a lower temperature
Temporal countercurrent exchange =
- Air inhaled = warm air + add water
- Air exhaled = cool air + remove water
- Mammals lose more water when in a warmer environment
Excretory water loss =
Water loss in urine production
- concentrate urine to retain water
- make poorly soluble or insoluble nitrogenous wastes so don’t need as much water (Desert animals)
Terrestrial amphibians
- Humidic - high evaporative water loss
- Isosmotic urine (Do not drink)
- Use bladder for water storage , NaCl actively transported
Desert lizards
Eat primarily insects + plants
- High water content
- Low metabolic rate
- Low respiratory evaporative water loss
- Nitrogenous waste = uric acid or urate salts
- Behavioral adaptations (shade + sun)
Small desert mammals
Eat insects + plants
- Higher metabolic rate
- Higher respiratory evaporative water loss
What was an adaptation to gain water in desert lizards?
Thorny devil sucks water up in skin grooves
Large desert mammals - Oryxes
Modulate core body temperature
- reduce water use for thermoregulation
- get water from food so can live for months or years w/o drinking
