Osmoregulation Flashcards
Crab molting
When a crab sheds its old exoskeleton, it takes on water in a carefully orchestrated way of swells. These wells crack open the old exoskeleton so that the crab can pull itself out.
Fluids and body weight
In humans, about 60% of our bodyweight is in fluids. These fluids include intracellular fluid which makes up the majority of the 60%, and the extracellular fluids blood plasma and interstitial fluid making up the rest.
Anatomy of body fluids
Picture a series of capillaries, like branches on a tree with spaces in between. The blood plasma is contained within the capillaries. In the gaps between the caps, there are cells filled with intracellular fluid. Between these cells is interstitial fluid. The Interstitial fluid is separated from the caps by the endothelial cells of the capillary walls.
Approximate osmotic pressure of seawater
1000mOsm (milliosmolarity)
Regulator vs conformer
A regulator maintains their blood osmotic pressure regardless of the ambient osmotic pressure, where a conformer changes their blood osmotic pressure to match the ambient osmotic pressure (like endo and ectotherms but for osmotic pressure).
Regulators and conformers in reality
in reality, osmotic regulators/conformers are not always able to perfectly maintain/match their blood osmotic pressure. In shrimp (regulator), they maintain their BOP within a specific range. In green crabs they are actually both, maintain their BOP in ambient OPs of 500 or less, somewhat conforming in ambient OPs between 500 and 1000, then conforming once ambient OPs reach 1000 mOsm.
Salinity trends in Chesapeake bay
At the top (most inland point) of the bay, Salinity is bellow 5g/Kg, which increases to over 25g/Kg at the mouth of the bay 250 km away. This distribution fluctuates based on time of day as the tide rises and falls, as well as through the seasons. For example, during spring rainfall the entire system is more diluted with freshwater and therefore has lower salinity
Blue crabs in Chesapeake bay
Blue crabs are abundant in this area and other estuaries along the Atlantic and gulf coasts in the USA. When ambient osmotic pressure and salinity are low (>1000 mOsm and >35 g/Kg) they function as regulators, however once AOP and Salinity pass these thresholds, the function as conformers.
U/P ratio
a measurement that compares the concentration of a substance in urine to its concentration in blood plasma, indicating how effectively the kidneys are concentrating or diluting urine
U/P ratio = 1 (isosmotic)
Effect on water excretion: Water is excreted from the body in the same balance with other dissolved substances as found in the blood.
Effect on solute excretion: Solutes are excreted from the body in the same balance with Water as found in the blood.
Effect on blood osmotic pressure: Formation of urine leaves ratio of solutes to water in blood plasma unchanged thus it does not alter blood osmotic pressure
What does U/P ration effect
-Water Excretion
-Solute Excretion
-Blood osmotic pressure
U/P ratio < 1 (hypoosmotic)
Effect on water excretion: Water is removed more than solutes, so the urine is more diluted than the blood.
Effect on solute excretion: The body keeps more solutes (salts/waste) and removes more water, so urine is more diluted than blood.
Effect on blood osmotic pressure: Ratio of solutes to water in the blood is shifted upward, so blood osmotic pressure increases
U/P ratio > 1 (hyperosmotic)
Effect on water excretion: The body holds onto more water and removes more solutes, making urine more concentrated than blood
Effect on solute excretion: Your body gets rid of more solutes than water, making urine more concentrated (saltier) than blood.
Effect on blood osmotic pressure: Ratio of solutes to water in the blood is shifted downward, so blood osmotic pressure decreases
Cell volume regulation
-Recall: water moves to where there is more solutes
-When a cell is moved into a more dilute solution, it initially swells with water. To regulate its size back to normal, it must reduce the content of dissolved entities within itself, causing water to flow out.
-When a cell is move into a more concentrated solution, it initially loses water and shrinks. To regulate its size back to normal, it must increase the content of dissolved entities within itself, causing water to flow in.
