BIL360 | FE | L5 Water & Salt Physiology 2
Terms in this set (58)
When examining water and salt physiology, always consider:
- evolutionary history
- enviro cond
FW teleost: evolutionary history
FW teleost: body
FW teleost: challenges
1. gain H₂O via osmosis
2. lose ions via diffusion
FW teleost: adaptations
1. dilute urine to void xs H₂O
2. actively transport ions to gills
SW teleost: evolutionary history
FW vertebrate animals
(moved from SW -> FW -> SW)
SW teleost: body
SW teleost: challenges
1. lose H₂O via osmosis
2. gain ions via diffusion
SW teleost: adaptations
1. dec H₂O loss in urine
2. drink SW
3. actively transport monovalent ions to gills
4. excrete divalent ions in urine
SW reptiles/birds/mammals: evolutionary history
SW reptiles/birds/mammals: body
SW reptiles/birds/mammals: challenges
1. lose H₂O via osmosis
2. gain ions via diffusion
How do SW reptiles/birds/mammals prevent water loss?
less permeable integument
How do SW mammals prevent ion gain and water loss?
How do SW reptiles/birds prevent ion gain and water loss?
extrarenal salt secretion
energetic costs of regulation depend on:
rate of passive exchange of ion/water
rates of passive exchange of ions/water are affected by:
1. blood/enviro gradients
How do osmotic P compare b/w FW and SW animals?
FW animals have lower osmotic P
dec gradient b/w enviro and plasma, low rate of water gain and ion loss, and dec energy needed to maintain normal plasma composition
How does a low osmotic P affect gradients b/w body fluids and enviro?
How do FW reduce passive exchange?
integuments with low permeability
Where in the body does most passive exchange occur?
across the gills
regulatory mech of FW animals
- large amounts of dilute urine that is hyposmotic to blood (U/P < 1)
- active ion uptake
how do kidneys help FW fish regulate?
ion, volume (void excess water) - in conflict w/ each other in FW animals
How do FW fish deal with water gain?
kidneys limit [ion] in urine, but still a loss of ions
What is conflict for FW fish using urine to regulate?
volume conflicts ions
How do FW fish deal with ion loss?
actively transport major ions from water to gills while removing metabolic waste
chloride pump in gills
exchanges bicarbonate for Cl
sodium pump in gills
exchanges H for Na
FW animal ion pumps are electro_____
marine animal ancestry
- some completely marine
- some moved to FW and land, then returned to sea
cuttlefish ancestry & blood plasma
triggerfish ancestry & blood plasma
How do marine inverts differ from SW?
although isosmotic to SW, differ in particular ions
only marine vert with exclusively marine ancestry
- primitive jawless fish
- only VERTS with exclusively marine ancestry
- similar in osmotic & ionic relations to marine inverts
compare body fluid osmotic P for FW teleosts, marine inverts, and SW teleosts
FW teleost < SW teleost < marine inverts
relative to SW, marine teleosts have ______ body fluids
to replace water lost by osmosis, teleost fish:
- drink SW to cause diffusion of body water into SW in gut
- in later parts of the gut, Na and Cl are actively transported into the blood to favor osmotic uptake of water into the blood
SW teleosts excrete excess divalent ions by:
urine excretion (isosmotic to plasma U/P = 1)
ionic U/P ratio of ions < 1
SW teleosts excrete excess monovalent ions by:
gills (U/P > 1)
SW teleosts limit urine production bc:
ionic regulation via urine production conflicts w/ osmoregulation
What can be voided across gills?
- nitrogenous wastes
... without any water!
How are ions voided across the gills?
- Na-K pump creates electrochemical gradient favoring Na+ diffusion out of cell
- Na+ diffuse into cell at NKCC w/ K+, 2 Cl-
- Cl- entry creates gradient favoring diffusion out of cell via Cl- channels
basically pump Na out, create gradient that draws Na back in along with Cl, K returns to blood, and Na is pushed out of the cell
How do SW fish excrete Na+
active or passive depending on spp
primary site of osmoreg in fish
FW teleosts are hy__osmostic to surrounding
- active uptake of ions at gills
- produce dilute urine
SW teleosts are hy__osmotic to surrounding
- ingest SW
- excrete ions in urine and across gills
compared to the blood, reptile and bird urine is:
How do reptiles and birds deal with excess salt?
extrarenal excretion via salt glands (excretions are saltier than SW!)
compared to the blood, mammal urine is:
most conc of all verts!
How does urine conc compare b/w terrestrial and marine mammals?
marine elasmobranchs are hyp__osmotic and hyp__ionic
hyper (blood conc)
...but hypoionic to SW (blood ion conc lower than SW)
elasmobranch blood conc of ____ and ___ are low while _____ and _____ are high
low: Na, Cl
high: urea, TMAO (trimethylamineoxide)
How do elasmobranchs gain water and salt?
- rectal gland secretions: rich in monovalent ions (Na, Cl)
- feces: salt, water
- urine: hyposmotic to plasma, rich in divalent ions (Mg, SO4)
what is different about elasmobranch osmo and salt reg?
TMAO fxn in elasmobranchs
counteract effect of urea to protect proteins
nitrogenous waste products:
- mammal/elasmobranch: urea
- teleost: ammonia
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