Water and electrolyte balance Flashcards
How do marine bony fish maintain hypotonic homeostasis?
Water diffuses out of the fish while salt diffuses in. In an effort to prevent isotonicity, the fish pumps salt out via chloride cells. Marine fish must intake more water in order to replace what was lost.
How do freshwater fish maintain hypertonic homeostasis?
Salt diffuses out of the fish while water diffuses in. Chloride cells pump salts into the fish to maintain hypertonicity, and the fish must urinate more to eliminate extra water.
What are some methods of waste removal?
Protozoans use contractile vacuoles, flatworms use protonephridia, and segmented worms and mollusks use metanephridia with “tubings”
What function do nephrons fulfill in mammalian urinary systems?
Nephrons maintain the water and ion balances in the blood.
How does the renal corpuscle carry out its primary function as a filter?
“Dirty” blood enters the glomerulus which filters most of the water and small molecules. Large molecules like proteins and cells stay in the “clean” blood.
How does the proximal tubule utilize Na/K-ATPase?
Nutrients are transported into the lumen using an electrochemical gradient. Nutrients then diffuse into blood vessels
How do the descending and ascending limbs of the Loop of Henle promote an osmotic gradient?
The Loop of Henle uses countercurrent exchange where water diffuses out of the descending limb, creating an osmotic gradient for Na and Cl to be passively and actively transported out of the ascending limb. The vasa recta (blood vessels) maintains the osmotic gradient by removing water.
What roles do hormones play in regulating water and electrolyte balance?
Antidiuretic hormone (ADH) triggers an increase in the number of aquaporins in the distal tubule to resorb water if an individual is dehydrated. Diabetes insipidus is caused by the absence of ADH.
Aldosterone signals the resorption of water and Na when blood flow decreases due to low Na levels.
