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Osmotic and Ionic Regulation. All animals face osmotic and ionic stresses. Stresses depend on environment: Aquatic Marine Freshwater Brackish (estuarine) Terrestrial. Regardless of their environment, all animals must be capable of maintaining isosmoticity between - PowerPoint PPT Presentation
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Osmotic and Ionic Regulation
All animals face osmotic and ionic stresses.
Stresses depend on environment:• Aquatic
• Marine• Freshwater• Brackish (estuarine)
• Terrestrial
Regardless of their environment,all animals must be capable of
maintaining isosmoticity betweenthe ICF (intracellular fluid) and
ECF (extracellular fluid).
Regulating ICF osmotic conc. in responseto changes in the osmotic conc. of the ECF
is called:
Cell Volume Regulation
HYPERTONIC HYPOTONIC
Unchecked swelling under hypotonicconditions can lead to
OSMOTIC LYSIS
If the osmotic conc. of the ECF decreases,water moves into the ICF and the cell swells.
H2O
RegulatoryVolume
Decrease(RVD)
If the osmotic conc. of the ECF increases,water moves out of the ICF and the cell shrinks.
H2O
RegulatoryVolumeIncrease
(RVI)
RVI - Ionic Fluxes
osmoticallyshrunken
cell
Na+
H+
Cl-
HCO3-
H2O + CO2
H2O
H+
K+
Cl-
HCO3-
H2O + CO2
H2Oosmoticallyswollen
cell
RVD - Ionic Fluxes
ICFcontent
FWSW
H2O
F.A.A.
F.A.A. = free amino acids
FW SW
ICFcontent
Days0 15
H2O
F.A.A.
Animals can reduce the amountof volume regulation their cells
must do by regulating ECF osmoticconcentrations.
Osmotic and ionic regulation occursin both aquatic and terrestrial spp.
We’ll look at aquatic organisms first
Medium osmolarity (mOsm)
0 1000
1000
EC
F o
smol
arity
(m
Osm
)
isosmoticline
osmoconformer
osmoregulator
Stenohaline - able to tolerate a narrow salinity rangeEuryhaline - able to tolerate a wide salinity range
Volume changes on transfer to dilute seawater