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BMS107 > Osmoregulation > Flashcards

Osmoregulation Flashcards

1
Q

Definitions;

  • Osmoregulator
  • Osmoconformer
A
  • Osmoregulator: Controls extraceullular solute profile
    • is most vertebrates
    • Ensure that internal ion and water composition
  • Osmoconfomer: Exerts little control over their extracellular solute profile
  • Stenohaline animal: can only deal with a narrow range of osmolarities
  • Euryhaline animal: can tolerate a wide range of osmolarities
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2
Q

Metabolic water

  • what is it, how much water produced
  • e.g. of animal that relies on it
  • Carbohydrates, fats and protein H2O content
A
  • Metabolic water is water generated as a result of oxidative phosphorylation
    • for every mol of glucose, 6 moles of water produced
  • small desert animals mainly rely on this method for obtaining water
  • Carbohydrates: 0.56g H2O/g food
  • Fats: 1.07 g H2O/g food
  • Proteins: 0.40 g H20/g food
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3
Q

Performed water

  • what is it
  • % water in different types of food
A
  • Performed water: Water associated with food

- dry seeds = 5 - 10%; insects, meat = 60-70%; pasture = 80-90% and nectar = 80-95%

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4
Q

Classification of Solutes (3)

  • what it does
  • e.g.
A
  1. Perturbing: Disrupt macromolecule function
    • Na, K, Cl, SO4, charged a.a.
    • as conc increases, enzyme has to work harder
  2. Compatible: little effect; polyols (glycerol, glucose) and uncharged amino acids
  3. Counteracting: Disrupt function on own but counteract disruptive effects of another solute when in combo
    • Urea disrupts and methylamines strengthen hydrophobic interactions -> together = little effect
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5
Q

Molarity (calculation)

A
  • number of moles of solute present in 1 litre of solution (expressed in mol/L)
    • mol = grams/MW
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6
Q

Osmolarity - definition

A

-Osmolarity: Total osmotic activity in a solution as the sum of the individual osmotic activities of all the solutes in the soln.

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7
Q

Nitrogenous Excretions

  • how it comes about
  • 3 types
A
  • a.a. used in proteins and other nitrogen-containing molecules
    • when a.a. oxidised or converted to other kinds of molecules, the amino group must be removed
  • nitrogenous wastes are ammonia, urea or uric acid
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8
Q

Nitrogenous excretions; Ammonia

-basics - when produced and what transformed into

A
  • Produced during a.a. and other nitrogen-containing molecule breakdown
  • Is toxic and must be excreted
  • Can be transformed into other forms (urea and uric acid)
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9
Q

Ammonia -> Advantages and disadvantages

A

Advantages: direct end-product of deanimation of a.a. therefore requires no extra energy
-highly soluble in water
Disadvantages: Very toxic (needs 400ml H2O to dilute each gram)
-must be excreted rapidly or converted to less toxic form

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10
Q

Urea -> Advantages and disadvantages

-where produced

A

Advantages: -Less toxic than ammonia (10 x less water for storage)
-Highly soluble (can be moderately conc to conserve water)
Disadvantages: -Requires more energy to produce than ammonia
-Fair amount of water needed for its storage and excretion

*produced in the liver

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11
Q

Uric acid (Urate) -> Advantages and disadvantages

A

Advantages: -Produced in concentrated crystal form (saves water)
-Low toxicity
-Can be stored
Disadvantages: synthesis requires more energy

*important in egg-laying terrestrial vertebrates

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12
Q

Nitrogen Excretion - General rules as to what organisms excrete what

A
  • Teleost fish -> ammonia and urea
  • Chondrichthyes -> urea
  • Amphibians -> Ammonia, urea and uric acid
  • Birds and reptiles -> uric acid
  • Mammals -> urea

Varies with;

  • Life stages (tadpoles - ammonia to frogs - urea)
  • Diets (hummingbirds - high conc = uric acid; low conc nectar = ammonia)
  • Species/breed: dalmation dogs = uric acid
  • Habitat: turtles/tortoises
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13
Q

Marine Fish:

-When marine environment has higher osmolarity than fish

A
  • Marine teleosts (bony fish)
  • hypotonic to medium (higher osmolarity in external enviro)
  • Drink lots of seawater
  • Chloride cells in their gills excrete salts
  • Kidneys - few or no glomeruli
  • Urine volume very small (no bladder)
  • most solutes move in to animal and H2O moves out (need to continually remove solutes and get H2O in
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14
Q

Marine fish;

-When fish has about the same osmolarity as external environment

A
  • “primitive fish” and cartilaginous fish are iso-osmotic with sea water
  • conc solutes in tissues of osmoconfomers is similar to ocean
    • high solutes conc due to urea and TMAO
  • well-developed kidneys
  • specialised rectal gland excretes excess salts
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15
Q

Freshwater vertebrates;

-When osmolarity is higher in fish than environment

A
  • Freshwater teleosts
  • Do NOT drink water - gain water from environment by osmosis
  • Produce large quantities of dilute urine
  • Chloride cells in the gills use active transport to pump salts into their body
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16
Q

Osmoregulation - water balance

A
  • Input + production = utilization + output
  • What comes in body must eventually be used for excreted to maintain homeostasis
    • done either by diet, environment, behaviour and thermoregulation
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17
Q

Main electrolytes in ECF and in ICF

A
  • K and HCO3 are high in the intracellular fluid

- Na and Cl are high in the extracellular fluid

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18
Q

The integument in osmositic balance

A
  • The Integument: Can mediate the permeability by changing amount of aquaporin proteins
    • can add mucous to decrease H2O loss (frogs)
    • thick integument also makes skin impermeable
19
Q

Amphibian generalisations (H2O control) (3)

-Exceptions

A
  • Are highly dependent on water
  • skin is permeable to water (waxy secretion can decrease permeability)
  • No loops of Henle - means can’t concentrate urine

EXCEPTIONS;

  • several arid-adapted spp. can store urates in bladder (usu. adults secrete urea)
    • also sheds skin to act as a cocoon)
  • Water-holding frog burrows and aestivates and stores watter
20
Q

Reptiles -> H2O control

  • thinks they can do to decrease water loss
  • waste they produce
A
  • Have a relatively resistant integument (virtually waterproof)
  • Cutaneous Evaporative Water loss (EWL) is still major water loss
  • Can decrease respiratory EWL as can decrease metabolic rate and therefore low respiratory rate
  • Simple kidneys (w/ no loop of Henle)
  • obligatory drinking uncommon
  • Produce urates
  • reabsorb water at cloaca (via salt transport)
  • Nasal salt glands
  • very dry poo
21
Q

Birds -> H2O Control

  • types of nephrons
  • waste
  • other features
  • birds near ocean
A
  • Have 2 types of nephrons -> ‘reptile-like’ and ‘mammal-like’
    • i.e. one with no loop of henle, one with
    • nephron v. lobular
  • Most birds only form modestly hyperosmotic urine (can get up to 3 x plasma concentration -tho mammals can get up to 27 x)
  • waste = urate (crystals therefore no osmotic pressure)
  • most lack urinary bladder
  • cloaca and lower intestine can recover water
  • nasal salt glands remove excess salt (excrete hyperosmotic solutions of Na and Cl via countercurrent system)
    • only those that live near sea (allows them to consume seawater)
  • Birds pant to try and cool down -> decrease foraging when temp hot
  • EWL increases as temp increases
22
Q

Mammal behaviour to control H2O loss

A
  • Limit activity in the heat of day
    e. g. being nocturnal, reducing metabolic rate and breathing (alter volume, NOT rate)
  • Diet (alter feeding times or plant sp.)
  • Retreat (burrow, shade or orientation)
  • Thermoregulation
  • Drinking
    e. g. Bedoin goat can drink every 2-4 days (stomach lining acts as an osmotic barrier)
23
Q

Mammals -> EWL

-adaptations to minimise EWL

A
  • Lose more water through EWL than other groups
  • selective brain cooling (carotid rete) plays a role in reducing EWL
  • some have specialised nasal adaptations (e.g. camels and dik-diks)
    - warmer air holds more H2O - if not fully saturated, have to do so when breathed in
    - when breathe out through mouth, can lose a lot of water
    - longer nose = better at retrieving more H2O; is a countercurrent multiplier (is an evaporative cooling)
24
Q

Faecal water loss in mammals

-urine too

A
  • desert rodents have approximately 21-37%
    • dik-dik, goat = 40-50%; horses/cow = 70-80%
  • Produced concentrated urine -> thru well developed loops of henle
    • it’s all about how they use structure
25
Q

Countercurrent Multiplier Definition

A
  • A structure in which two fluids flow in opposite directions on either side of an exchange surface, allowing high-efficiency exchange of materials by active means
    e. g. ion concentration in the loop of Henle
26
Q

6 Roles of the Kidney

A
  1. Ion Balance
  2. Osmotic Balance
  3. Blood pressure
  4. pH balance
  5. Excretion
  6. Hormone Production

*are less than 1% of body mass, but take 20 % of cardiac output

27
Q

The Nephron

-2 general parts

  • Glomerulus + Bowman’s capsule
    • fluid relationship
A
  • The functional unit of the kidney
  • Made of renal tubule and associated vascular
    • Renal Tubule = tube from single layer of epithelial cells
  • Gomerulus = twisted ball of capillaries that delivers fluids to the tubule
  • Bowman’s capsule = mouth of tubule (cuplike expansion that surrounds the gomerulus
    • fluids that leave glomerulus enter Bowman’s capsule and move down PC tubule
    • blood cells and large macromolecules are not filtered
28
Q

Blood Supply to Nephron

A
  • Blood enters Kidney via renal artery
  • Afferent arteriole enters glomerulus, efferent leaves
    • efferent flow into peritubular capillary beds that wrap around tubules (in cortical)
    • also found around PCT and DCT
      - in juxtamedullary, efferent diverges into vasa recta (run along loop of Henle)
      - vasa recta prevents dissipation of osmotic gradient while supplying nutrients and removing wastes
29
Q

Tubule Regions

definitions of;

  • Filtration
  • Reabsorption
  • Secretion
  • Excretion
A
  • Proximal Tubules: Mass reabsorption
  • Loop of Henle: Generates the interstitial concentration gradient
  • Distal tubule: reabsorption completed for most soluts
  • Collecting duct: drains multiple nephrons

Filtration” basis of size - fluid from blood to tubules
Reabsorption: Take out of filtrate that we want in blood
Secretion: blood to tubule
Excretion tubule to external environment

30
Q

Filtration, Reabsorption, Secretion and Excretion in Nephron

A
  • Filtration: Gomerulus
  • Reabsorption: PCT, Ascending and Descending limbs of loop of henle, DCT and Collecting duct
    • PCT is most important in reabsorption of H2O
  • Secretion: PCT, DCT, Collecting Duct
  • Excretion: Collecting Duct
31
Q

Anti-diareutic hormones on aquaporins in collecting duct

A
  • ADH absent: No reaborption of water = dilute urine
  • ADH present = reabsorption of water = concentrated urine

*ADH present increases aquaporins, enables water to be uptaken in collecting duct

32
Q

Filtration -> Glomerulus

  • Glomerular capillaries
  • Mesangial cells
A
  • Glomerular capillaries are very leaky -> have foot processes that make filtration structure
  • Mesangial cells control blood pressure and filtration within glomerulus
  • Hydrostatic pressure w/in glomerulus determines how much fluid is pushed into renal corpsule
33
Q

Primary Urine

  • What it is it
  • What happens to it later on
A
  • Primary Urine: initial flitrate filtered in Bowman’s Capsule that is isosmotic to blood
    • most water and salt in primary urine is reabsorbed using transport proteins and energy
34
Q

Secretion

A
  • Secretory products include K, NH4, H, pharmaceuticals and water-soluble vitamins
  • requires transport proteins and energy
35
Q

Features of Reabsorption and Secretion

A
  • Are highly selective

- Some materials are actively reabsorbed (glucose and Na) others follow by passive diffusion (water)

36
Q

Excretion

  • parts
  • micturition reflex
A
  • After urine produced, leaves kidney and enters the urinary bladder
  • urine lives the bladder via the urethra
  • opening and closing of sphincters is controlled by a spinal cord reflex arc that can be influenced by voluntary controls
37
Q

Basic Renal processes

-Fate of Urea, uric acid and glucose in filtrate

A
  • Glucose: reabsorbed back into bloodstream via active transport
  • Urea: Most left in filtrate - a little bit reabsorbed
  • Uric acid: too big to be filtered in glomerulus, but secreted into filtrate later
38
Q

Conserving water via filtrate

A
  • High plasma osmolality
  • low blood pressure

*due to decreasing Glomerular filtration rate

39
Q

Producing copious dilute urine via filtrate

A
  • low plasma osmolality
  • high blood pressure

*Due to increasing Glomerular filtration rate

40
Q

Hummingbirds and Aestivating frogs - adaptation

A

-Both shut down glomerular filtration to save energy (kindeys use up to 16% body’s ATP)

41
Q

Cortical and Juxtamedullary nephrons

-relationship between loop of henle length and osmolality of urine

A
  • Cortical: Nephrons that primarily sit in the cortex -> have a short loop of Henle that doesn’t contribute much to osmotic gradient
  • Juxtamedullary: Sit closer to the corticomedullary junction -> have a longer loop of henle
    • create strong concentration gradient inside kidney
  • Animals that produce more concentrated urine have a longer loop of henle and a thicker medulla
    • maximum urine osmolality and medullary area proportional (directly)
42
Q

Loop of Henley and Collecting Ducts

  • what are they classified as?
  • What osmotic conc of final urine depends on
A
  • Both act as countercurrent multipliers: create osmotic gradients that facilitate tranpsort processes
    • gradients maintained by vasa recta capillaries
  • Osmotic con. of final urine depends on permeability of the distal tubule and collecting duct
    • impermeable = dilute; permeable = concentrated
43
Q

Antidiuretic Hormone

A
  • Controls urine volume
  • secreted from pituitary gland (under control of hypothalamus)
  • binds to receptors on DCT and collecting ducts and stimulate production of aquaporins
  • Called arginie vasopressin in most mammals

*inhibited by alcohol and caffeine

44
Q

Case example of H2O retention by Kangaroo Rat

A
  • Never have to drink: rely on metabolic water and some preformed water
  • Nocturnal
  • Avoid movement while in burrow to decrease heat production
  • dry food stored in burrow absorbs moisture lost in breathing
  • Noses cool oxygen leaving nose - decreases EWL
  • Large intestine absorbs alsmost all water in digestive tract (hard, dry faeces)
  • Concentrated urine produced

BMS107 (15 decks)

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