Osmoregulation Flashcards
Osmoregulation
Maintaining water and salt balance in the animal body. Also The selective retention and excretion of water and salt from the body
Terrestrial
can dehydrate so need to retain water
Aquatic
need to maintain salt balance
Marine
Depends on living in freshwater or salt water
osmosis
Water molecules move across a selectively permeable membrane from a region of high concentration to a region of low concentration
Osmolality
-Osmotic concentration(osmotic pressure) of a solution.
- Number of osmoses per kg of solute
- osmotic concentration measured in osmoles
Hyperosmotic
Solution has a high osmolality on one side of a membrane
Hypoosmotic
Solution has a low osmolality on one side of a membrane
Isoosmotic
Solutions on both sides of the membrane have the same osmotic concentration
Osmoregulatory system
-Regulate water/solutes in blood, secondarily in interstitial fluid
-cells also have some ability to alter their cell volume
Cell Volume regulation
Cells have limited ability to alter volume through ion and water movement
-ECF provides more stability for cellular functions
Ion concentration Management
intracellular ion concentrations are critical for
- Macromolecule function
-enzyme and protein performance
Membrane constraints
- cells have a semipermeable membrane
- ICF must be closely regulated without major disruptions
Fluid Composition
-Interstitial fluid and blood plasma are regulated to be very similar
-most cells can maintain ionic differences across cell membranes
-use ATP to regulate intracellular ion composition
Perturbing
-Disrupt macromolecular function
-Na+, K+, Cl-, SO4+ charged amino acids
Compatible
-Little effect on macromoleculecular function
-Polyols (glycerol, Glucose) and uncharged amino acids
Counteracting
-Disrupt macromolecular functions on their own
-Counteraction Disruptive effects of other solutes when employed in combination
Transcellular transport
-Movement through the cell across membranes
Paracellular transport
- Movement between cells
- “leaky” vs. “tight” epithelia
Types of transporters
-Na+K+ATPase, Ca2+ -ATPase
-Ion channels (Cl-, K+, Na+, Ca2+)
-Electroneutral Cotransporters
-Electroneutral exchangers
Movement of Water
Water moves from low solute concentration (High water potential) to high solute concentration (Low water potential) —–> Osmotic gradient
Osmolarity and volume
Changes in osmolarity causes a trans-membrane osmotic gradient, and therefore water moves across the membrance affecting cell volume
Osmolarity
is the measure of solute concentration (number of osmoles per liter)
Examples
1 mol of glucose= 1 osmol
1 mol of NaCl = 2 osmol
Cell volume regulation
A critical problem faced by all cells: Maintenance of a constant
volume in the face of extracellular and intracellular osmotic
perturbations
* Most cells respond to swelling or shrinkage by activating
specific membrane transport and/or metabolic processes that
serve to return cell volume to its normal resting state
* Volume sensing mechanism are extremely sensitive, cells can
sense and respond to volume changes of ~3%
Ionic regualtion
-concentration of specific ions
volume regulation
total amount of water in a body fluid
Osmotic regulation
osmotic pressure of body fluids
Osmoregulators
-Maintain extracellular osmolarity and ion composition constant
-Strict extracellular osmotic homeostasis
- cells and tissues are not able to cope with changes in extracellular osmolarity and ion concentration
Osmoconformers
-Do no actively control the osmotic conditions of the extracellular environment, but may control extracellular osmolytes
- high degree of cellular osmotic tolerance
