Osmoregulation Part Two Flashcards
Osmoregulators are able to maintain what regardless of osmotic changes in the external environment?
Osmoregulators maintain a steady extracellular fluid (ECF) osmotic pressure.
Marine osmoregulators are usually: hypo-osmotic or hyper-osmotic?
Hypo-osmotic, with an inside of 400 mOsm and an environment of 1000 mOsm.
Freshwater osmoregulators are usually: hyper-osmotic or hypo-osmotic?
Hyper-osmotic, with an inside of 300 mOsm and an environment of <5 mOsm.
What is important about hypo-osmotic osmoregulators?
They maintain extracellular fluid and cellular osmotic concentrations of 250-400 mOsm. They have low concentrations of organic osmolytes, and marine animals must drink seawater and absorb NaCl in order to absorb water, creating an excess of salt in the blood.
Gills use epithelial chloride cells to actively transport Na+ and Cl- outward.
What is important about hyper-osmotic osmoregulators?
They must cope with the low osmolarity of freshwater. Valuable solutes are lost through the gills, but they have several mechanisms for regulating extracellular fluid osmolarity. These mechanisms include: the active uptake of ions across the gills and skin, hypotonic fluid excretion by kidneys or other structures, lower internal osmolarities, and low permeability of integument.
True or False: Some fish can alternate between modes of osmotic adaptation.
True. For example, they can be hypo-osmotic in oceans but hyper-osmotic in rivers. This is done through acclimatization regulation coupled with an anticipation mechanism.
In water animals are Salt Glands found?
Marine birds and reptiles; helps with salt water because they may never have access to fresh water and due to the ion concentration, the kidneys are unable to obtain water from the sea.
What does the Salt Gland consist of?
Ducts, nostrils with salt secretions, and nasal salt glands that are two structures located above the eye and are osmoregulator organs. They secrete a hyper-osmotic NaCl solution through active NaCl transport, allowing the animal to drink sea water. This is a countercurrent exchange with the blood, offering the maximum transport rate.
How much water does a Salt Gland-lidded animal get per litre of salt water?
They get .5 litres of water per 1 litre of saltwater.
In the regulation of salt glands in birds, what happens to the kidneys with a high intake of saltwater?
The kidneys shut down to help with water conservation with a high blood osmolarity/high intake of seawater.
What stimulates nasal salt glands?
Corticosterone.
What is the Kidney?
A group of organs that share one property - they produce a primary fluid, primary urine, that goes through a series of tubes to produce urine. It is an internal organ mostly concerned with osmoregulation, that has common architectural and physiological principles.
Where in the Kidney does major changes in the osmotic concentration of urine take place?
In the Distal tubule; minor change in osmotic concentration take place in the proximal tubule.
Where in the Kidney does major changes in ionic concentration take place?
In the Proximal tubule.
What occurs with the blood in the collecting area?
This first step leads to primary urine (the urine before further modification). There are two different mechanisms that lead to primary urine; ultrafiltration (gradients are used to push fluid into and through the kidney) and active secretion (uses ATP to move ions that push water).
Why modify primary urine?
Primary urine is urine after the filtration step, and nearly all animals modify primary urine by retrieving and secreting solutes through active transport.
The primary urine is iso-osmotic with the body, and full of good solutes. The cells activate K+ Cl- channels in order to recover Sodium and chloride from the primary urine, but doesn’t allow water to cross. The remaining urine has half the concentration of the primary urine.
What are the Malpighian tubules?
An osmoregulatory organ (in insects) that can produce hypo-osmotic urine with a high concentration of NaCl (in Rhodnius prolixus, where the blood is 50% plasma [hypo-osmotic], half of body weight is excreted as urine).
