ch. 44 Flashcards
where do physiological systems of animals operate
in a fluid environment
osmoregulation
controls solute concentrations and balances water gain and loss
desert and marine animals
face desiccating environments that can quickly deplete body water
freshwater animals
conserve solutes and absorb salts from surroundings
overview of excretion
rids body of nitrogenous metabolites and other waste products
what is osmoregulation based on
balancing uptake and loss of water and solutes
driving force for movement of water and solutes
concentration gradient of 1+ solutes across plasma membrane
how does water enter and leave a cell
osmosis
osmolarity
solute concentration of a solution
- determines water movement across selectively permeable membrane
isoosmotic
water molecules will cross the membrane at equal rates in both directions
hypoosmotic
- lower solute concentration
- higher free H2O concentration
hyperosmotic
- higher solute concentration
- lower free H2O concentration
net flow of water
hypo osmotic to hyperosmotic
hypo
below
hyper
more
2 ways animals can maintain water balance
- osmoconformers
- osmoregulators
osmoconformers
isosmotic with their surroundings and do not regulate osmolarity
osmoregulators
expend energy to control water uptake and loss in a hyperosmotic or hypoosmotic environment
stenohaline
can’t tolerate substantial changes in external osmolarity
- most animals
steno
narrow
haline
salt
euryhaline
animals can survive large fluctuations in external osmolarity
eu
true
what are most marine invertebrates
osmoconformers (isosmotic)
what are many marine vertebrates and some marine invertebrates
osmoregulators
what are bony fishes to seawater
hypoosmotic
- water moves from bodies to sea water
- balance water loss by drinking large amounts of seawater and eliminating ingested salts through gills and kidneys
what is osmoregulation frequently coupled to
elimination of nitrogenous waste products
sharks and urea
- high concentration of urea in bodies
- trimethylamine oxide (TMAO) protects them from its denaturing effect
how do sharks take in and lose water?
- take in water by osmosis and food
- water disposed of in urine
- urine also removes some of salt that diffuses into shark’s body
osmoregulation in marine fish
- gain water through drinking seawater and food
- gain salts through drinking seawater and food
- lose salts through gills and urine
- lose water through gills/surface and urine
osmoregulation in freshwater animals
- gain water through osmosis from hypoosmotic environment and some drinking
- gain salts through food and gills
- lose salts through diffusion and urine
how do freshwater animals maintain water balance
drinking almost no water and excreting large amounts of dilute urine
animals in temporary ponds
lose almost all their body water and survive in a dormant state - anhydrobiosis
tardigrades (water bears)
dehydrate from about 85% water to 2% water in dehydrated, inactive state
how to land animals maintain water balance
- body coverings prevent dehydration
- anatomical features/behaviors - nocturnal desert
- eating moist food
- producing water metabolically through cellular respiration
what must osmoregulators do to maintain osmotic gradients
expend energy
what does amount of osmotic energy depend on
- how different animal’s osmolarity is from surroundings
- how easily water and solutes move across animal’s surface
- work required to pump solutes across membrane
transport epithelia
epithelial cells specialized for controlled movement of solutes in specific directions
how are transport epithelia arranged
complex tubular networks
ex. of transport epithelia
nasal glands of marine birds that remove excess NaCl from blood
most significant wastes
nitrogenous breakdown and products of proteins and nucleic acids
what do some animals do with toxic ammonia?
convert it to less toxic compounds before excretion
different forms of nitrogenous waste
ammonia, urea, uric acid
ammonia
- lots of water
- highly toxic
- little energy
- invertebrates: release across whole body surface
urea
- medium toxicity
- medium water
- more energy
what do most terrestrial mammals and many marine species excrete?
urea
- vertebrates: produced in liver, then carried to kidneys
uric acid
- little toxicity
- little water
- lots of energy
which animals excrete uric acid
insects, land snails, reptiles, birds
characteristics of uric acid
- doesn’t dissolve readily in water
- secreted as paste with little water loss
what does gout result in
production of uric acid as metabolic byproduct
how do most excretory systems produce urine
by refining a filtrate derived from body fluids
key functions of excretory systems
- filtration - body fluids
- reabsorption - reclaiming valuable solutes
- secretion - adding nonessential solutes/wastes to filtrate
- excretion - processed filtrated released from body
protonephridium
network of dead-end tubules that branch throughout body
- smallest branches of network capped by flame bulb
- excrete dilute fluid, osmoregulation
metanephridia
- in each segment of an earthworm
- tubules that collect coelomic fluid and produce dilute urine, osmoregulation
Malpighian tubules
- remove nitrogenous waste from hemolymph, osmoregulation
- conserves water effectively
where are Malpighian tubules found
insects and other arthropods
what waste do insects produce
dry waste matter mainly composed of uric acid
kidneys
excretory organs of vertebrates that function in excretion and osmoregulation
2 types of nephrons
- cortical - more in cortex
- juxtamedullary - more in medulla
filtrate produced in Bowman’s capsule
contains salts, glucose, amino acids, vitamins, nitrogenous waste, and other small molecules
descending limb of loop of henle
- reabsorption of water through channels formed by aquaporin proteins
- movement driven by high osmolarity of interstitial fluid (hyperosmotic to filtrate)
- filtrate becomes increasingly concentrated
ascending limb of the loop of henle
- salt but not water is able to diffuse from tubule into interstitial fluid
- filtrate becomes increasingly dilute
distal tubule
- regales K+ and NaCl concentrations of body fluids
- controlled movements of ions (H+, HCO3-) contribute to pH regulation
collecting duct
- carries filtrate through medulla to renal pelvis
- reabsorption of solutes/water
- urine hyperosmotic to body fluids
what is a key terrestrial adaptation of the mammalian kidney
ability to conserve water
why can hyperosmotic urine be produced
because considerable energy is expended to transport solutes against concentration gradients
2 primary solutes affecting osmolarity
NaCl and urea
concentrating urine in mammalian kidney
- proximal tubule: filtrate volume decreases, water and salt reabsorbed, osmolarity remains the same
- descending Henle: soluties becomes more concentrated, water leaving tubule by osmosis
what does NaCl diffusing from the ascending limb do
maintain a high osmolarity in the interstitial fluid of the renal medulla
what is expended to actively transport NaCl from filtrate in upper part of ascending limb
energy
countercurrent multiplier system (loop of Henle)
maintains high salt concentration in kidney
vasa recta
supplies kidney with nutrients without interfering w/ osmolarity gradient
osmolarity of urine
isosmotic to interstitial fluid of inner medulla, but hyperosmotic to blood and interstitial fluids everywhere else in the body
juxtamedullary nephron
key to water conservation in terrestrial animals
loops of Henle in dry environment animals vs. fresh water
- dry - long loops
- fresh water - short loops
kidney function in vampire bat
alternate rapidly between producing large amounts of dilute urine and small amounts of hyperosmotic urine
how do birds conserve water
- have shorter loops of Henle
- excrete uric acid instead of urea
where do reptiles reabsorb water from wastes
cloaca
- only have cortical nephrons
where do freshwater fishes conserve salt
in distal tubules and excrete large volumes of dilute urine
what is kidney function in amphibians similar to
freshwater fishes
how to amphibians conserve water on land
by reabsorbing water from urinary bladder
marine bony fish
- fewers/smaller nephrons than freshwater, lack distal tubule
- small or no glomeruli
- filtration rates lot, little urine excreted
- osmoregulation relies on specialized chloride cells in gills
what can mammals control the volume and osmolarity of urine in response to?
changes in salt intake and water availability
what kind of controls manage osmoregulatory functions of the mammalian kidney
nervous and hormonal
- contribute to blood pressure and blood volume
antidiuretic hormone (ADH)
activate membrane receptors on collecting duct cells
- initiates signal cascade leading to insertion of aquaporin proteins into membrane of collection duct
- increases water recapture to reduce urine volume
another name for ADH
vasopressin
where are ADH molecules released from
posterior pituitary
what do osmoreceptor cells in the hypothalamus monitor
blood osmolarity and regulate release of ADH
what happens when osmolarity rises above its set point
ADH release into bloodstream increases
- opposite for decrease in osmolarity
alcohol
- diuretic
- inhibits release of ADH
what can mutation in ADH production lead to
severe dehydration and diabetes insipidus
renin-angiotensin-aldosterone system (RAAS)
part of complex feedback circuit that functions in homeostasis
what can a drop in blood pressure near the glomerulus cause
justaglomerular apparatus (JGA) to release enzyme renin
renin
triggers formation of peptide angiotensin II
angiotensin Ii
- raises blood pressure
- decreases blood flow to kidneys
- stimulates release of aldosterone (increases blood volume and pressure)
what do ADH and RAAS both increase
water absorption
- only RAAS will respond to decrease in blood volume
atrial natriuretic peptide (ANP)
opposes RAAS
- released by atria of heart
when is ANP released
in response to increase in blood volume and pressure, inhibits release of renin
