13 to 15: Osmoregulation Flashcards Preview

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Flashcards in 13 to 15: Osmoregulation Deck (31):

How is the water balance maintained in the body?

What goes in the body must be used up or excreted. Eg diet, environment, behavior, thermoregulation
Input + production = utilization + output


Water gains: metabolic water
What is metabolic water

Water gains: metabolic water
Water generated as a result of oxidative phosphorylation
Ie carbs --> energy --> water
Dessert animals like small mice are highly dependent on metabolic water.
Eg camels store fat in their humps, to gain water they metabolism this fat


Water gains- preformed water
What is it and how do you get it?

It is water associated with food
Ie dry seeds -5-10%
Insects, meat 60-70%
Green Pasture 80-90%
What you eat will determine your preformed water intake


Water gains: electrolytes

By regulating their electrolyte concentration, cells can control their water content (through osmosis)
Main solutes:
K and HCO in intracellular fluid
Na and Cl in extracellular fluid


Electrolytes: classification of solutes

Distinguished by their effects on macromolecules
-disrupt macromolecule functions
-Na, Cl, K, SO4+, charged amino acids
-known to increase the Km of an enzyme
-little effect
-polyols (glycerol, glucose) and uncharged amino acids
-disrupt function on their own, but counteract disruptive effects of another solute when employed in combination
-urea disrupts and methylamines strengthen hydrophobic interactions; together there is little effect


How many moles in 9 grams of NaCl?

1 mole= 6.02 x 10^23
Then use:
Need molecular mass= 58.5
9/58.5 = .154 moles of NaCl


Molarity: number of moles of a solute psent in 1 litre of solution.
Calculate the concentration (mol/L) when 9 grams NaCl is dissolves in 1L of water

If the NaCl dissociates it will be an electrolyte, because they are charged molecules
The total osmotic activity in a solution is the sum of the individual osmotic activities of ll solutes in the solution
What is the osmolarity if 0.9% NaCl
0.154mol Na + 0.154 mol of Cl etc etc refer tonsoide


What is the difference between non-electrolytes and electrolytes?
Calculating their osmoles

Non electrolytes:
Covalent bonds that prevent dissociation in solution, so that no electrically charged species occur when they dissolve in water (mostly organic molecules)
Number of osmoles = number of moles

-Chemical compounds that dissociate in water into ions, and because ions are charged, then electricity can be conducted
-typically include inorganic salts, inorganic and organic acids and bases, and some proteins
-number of osmoles = sum of the number of moles of each electrolyte
Ie (solid)NaCl + H2O --> (ions) Na+ + Cl-


The total osmotic activity in a solution is the sum of the individual osmotic activities of all the solutes in the solution.
What is the osmolarity of 0.9% NaCl

??? Will do in class


Outputs: Nitrogen excretion

When amino acids are oxidized or converted to other kinds of molecules, the amino (NH2) group must be removed.

-nitrogenous wastes are ammonia, urea, or Utica acid (they are toxic and must be broken down) they are excreted in 3 forms
1. Ammonia
2. Urea
3. Uric acid


Outputs: nitrogen excretion- ammonia
What are the advantages and disadvantages

-direct end-product deanimation of amino acids, therefore the process requires no additional energy cost
-highly soluble in water

-very toxic- requires 400ml of water to dilute each gram to a non-toxic concentration
-must be excreted rapidly or converted to a less toxic form (eg uric acid or urea)


Outputs: nitrogen excretion- urea
What are the advantages and disadvantages

-less toxic than ammonia, doesn't need as much water to dilute it which makes it for better storage
-highly soluble: can be moderately concentrated to conserve water

-requires more energy to produce than ammonia does
-a fair amount of water needed for its storage and excretion


Outputs: nitrogen excretion -uric acid
What are the advantages and disadvantages?

-can be produced in a concentrated crystal form which saves water
-low toxicity- 50x less water for storage and excretion at non toxic concentrations
-can be stored

-synthesis of uric acid requires more energy than urea synthesis


Vertebrate kidneys have 6 roles what are they?

-ion balance-osmotic balance
-blood pressure
Ph balance
Hormone regulatio


One of the earliest signs of kidney failure in cats and dogs is incontinence what is it?

-kidney lose their ability to concentrate the urine effectively- reduced water reabsorption


How would you treat an animal with kidney failure?

-diet low in protein and phosphorus


Be able to label the kidney!

Kidneys receive 20% of cardiac output


Outline the path of urine through a nephron

Blood flows in through the afferent artery into the glomerulus. Filtrate (water and solutes) is filtered out to continue down the nephron. It travels through the proximal convoluted tubule then into loop of Henley (which determines the concentration gradient). It then heads to the distal convoluted tubule it goes through selective reabsorption and secretion. Then collecting duct: ADH absent: no reabsorption =dilute urine. If ADH is present urine will be concentrated.


What happens in the proximal tubule

Massvreabsorption. Eg Na, Cl, k, glucose,naming acids, vitamins, urea, choline.


Osmoregulation: the concept of balance
How do we maintain homeostasis of water?

Input + production = utilisation + output
Input + production: oxidation water, water in food, drinking water
Utilisation + output: evaporation from lungs, evaporation from skin, water in faeces, water in urine


What happens in the loop of henle

Generates the interstitial concentration gradient
Need to finish these notes on kidney


Marine teleosts (bony fish)
How about osmoconformers like sharks and rays? How do they survive in salt water?
How about fresh water vertebrates?

Are hypotonic to their medium
-drink sea water at 1% of their body weight/hour
-chloride cells in their gills excreting salts
-kidney have very few or no glomeruli
-urine volume is very small

-specialised rectal gland excreted excess salts

Freshwater vertebrates:
-don't drink water, gain it from osmosis and produce bulk urine
-chloride cells in gills use active transport to pump salts into their body


Terrestrial vertebrates generally must conserve water.

-amphibians are highly dependant on water
-skin is permeable to water
-no loops of henle: so can't concentrate urine
-tadpoles excrete ammonia
-adults excrete urea


Terrestrial vertebrates: reptiles

-have skin that is relatively resistant to water
-they loose most of their water from breathing
- so an adaption is that they have a low metabolic rate which gives them a low respiratory rates


Terrestrial vertebrates: birds

Have two types of nephrons- reptile like and mammal like
-with countercurrent loops of Henle-can form a concentrated urine
-most birds form not much hyper osmotic urine, however wage malarial as urate (precipitates as crystals and therefore excerts no osmotic pressure.
-most birds lack a bladder, the lower intestine recovers water


Terrestrial vertebrates: birds and reptiles near the sea

They consume large amounts of salt in diets
-nasal salt glands remove excess salt from body by secreting a concentrated salt solution
-reptiles and birds have salt glands-glands located near the eyes that drain into ducts that empty near the nostril
-excrete hyper osmotic solutions if Na and Cl
-hyper osmotic solutions are produced via ion pumps
-salt glands mean these animals can drink sea water


Terrestrial vertebrates: mammals-behaviour to reduce water loss

A) limit activity during heat of the day
-reduce metabolic rate and respiratory rate p
-breathing: alter volume not rate
B) diet:
-alter feeding times or plant
C) retreat
-burrow-water vapour
D) thermoregulation:
E) drinking:


Functions of the kidney: filtration

Blood pressure generates hydrostatic pressure gradient, forcing plasma into Bowbens capsule


Function of the kidney: re absorption

-most of the water and salt in the primary urine is re absorbed using transport proteins and energy


Function of the kidneys: secretion

Similar to re absorption but reverse!
-secretory products: K+, NH4+, H+, medicines, and water soluble vitamins
-requires transport proteins and energy


Functions of the kidney: reabsorption and secretion

Reabsorption and secretion are highly selective
-the proximal convoluted tubule is most important in reabsorption (70 % of water and solute are re absorbed here)
-som actively re absorbed eg glucose, Na+) others like water by passive diffusion