Explain how theprocess of filtrationand reabsorption inthe mammaliannephron regulatebody fluidcomposition The nephron is a regulatoryunit, meaning it absorbs orsecretes substances in orderto maintain homeostasis andconstant composition of bodyfluids.Proximal tube: Bicarbonateions are reabsorbed into theblood and hydrogen ions aresecreted out to maintain pH ofblood.The Loop of Henle: In thedescending limb, it ispermeable to water but notsalt. So water passes out of thenephron through osmosis. In the ascending limb, the walls are permeable salt not water, therefore salt passively passes out through the in the bottom, but is actively passed out in the top Distal tube: Selective reabsorption of sodium ions and potassium ions occurs here again to regulate the pH ofthe blood, and the concentration of salts. Collecting duct: This is the end of the nephron and connects to the ureters. The walls are permeable to water only, and water is transported out according to the bodies needs. The final filtrate is called urine.Outline the role of the hormones, aldosterone and ADH (anti-diuretic hormone) in the regulation of water and salt levels in bloodADH (Anti-Diuretic Hormone): Controls the reabsorption of water and concentration of salt through water retention by adjusting the permeability of the collecting ducts and the distal tubules. In high salt concentrations ADH levels increase, some distal tubules and collecting ducts become more permeable to water (more water is reabsorbed to return concentrations to normal). In low salt concentrations the ADH levels increase, but make the distal tubules and collecting ducts less permeable, meaning less water is absorbed.Aldosterone: Controls the amount of salt in the blood by regulating the reabsorption of salt in the nephron. Inhigh salt levels, levels of aldosterone decrease, resulting less salt being reabsorbed and less water diffusing in. Salt then decreases and blood volume/pressure also decrease. In low salt levels, the level of aldosterone are increased, so that more salt is reabsorbed and more water is diffusing in. The salt levels then increase, blood volume and pressure also increase.
Define enantiostasis as the maintenance of metabolic and physiological functions in response to variations in the environment and discuss its importance to estuarine organism in maintaining appropriate salt concentration Enantiostasis is the maintenance of metabolic and physiological functions in response to variations in the environment.