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Osmoregulation and Excretion: Sections 44.2,44.3, and 44.5 w/ some IB Topics Deanna, Stephanie, & Christen Nitrogenous Wastes Breakdown products of proteins and nucleic acids Ammonia: very soluble, highly toxic, tolerable only at low concentrations; excreted b/c animal needs access to lots of water; aquatic species; readily lost by diffusion across body surface / thru gills to surrounding H2O Urea: terrestrial animals (b/c less access to water for ammonia release); “produced in the vertebrate liver by a metabolic cycle that combines ammonia w/ CO2; 100,000x less toxic than NH3; disadvantage: must expend energy to produce urea from NH3 Uric Acid: relatively nontoxic; in insects, land snails, reptiles, birds; largely insoluble in water & excreted as semi-sold paste w/ lil water loss; adv for animals w/ lil water access but lots of energy to produce (so lots of ATP needed) Proteins Nucleic acids Nitrogenous bases Amino acids Pg. 927 –NH2 Amino groups Most aquatic animals, including most bony fishes Many reptiles (including birds), insects, land snails Mammals, most amphibians, sharks, some bony fishes O H C O Ammonia C O NH2 Urea C C C N C NH2 NH3 HN N N H H Uric acid O Influence of Evolution and Environment on Nitrogenous Wastes Depends upon an animal’s evolutionary history and habitat – esp availability of water Mode of reproduction affected which kind Adjusting to environment Shelled egg vs. shell-less egg or mammalian embryo Ex: certain tortoise changes from urea to uric acid when temp increases and water less available Amount produced depends on ‘energy budget’ – type of food Ex: endotherms eat more food so more wastes IB Syllabus! Arrows pointing to the IB slides in this presentation. 11.3.9: Explain the presence of glucose in urine of untreated diabetic patients Glucose is often present in the urine of untreated diabetic patients. This is because the glucose concentration of blood rises much higher than 90 mg per 100 ml, so the pumps in the proximal convoluted tubule can’t reabsorb all the glucose that is filtered out into the glomerulus. 11.3.8: Explain the differences in concentration of proteins, glucose and urea between blood plasma, glomerular filtrate and urine. Comparison of Fluid in the Kidney Content (mg per 100mg of blood) Blood in renal artery Urine Glomerular filtrate Blood in renal veins Glucose 90 0 90 90 Urea 30 2000 30 24 Proteins 740 0 0 740 Remember drawing this from yesterday? The next slide helps explain in more detail. 11.3.4: Explain the process of ultrafiltration, including blood pressure, fenestrated blood capillaries, and basement membrane. Function of glomerulus is production of filtrate from blood by ultrafiltration Blood plasma escape through walls of capillaries [remember video?], but in glomerulus 20% escapes (more than usual) Why this happens: Blood pressure very high b/c efferent arteriole is narrower than afferent arteriole Capillaries in the glomerulus are fenestrated (porous) These pores are large enough to let any molecules through, but on the outside of the capillary wall is a basement membrane composed of a gel of glycoprotein. It lets all substances in the blood plasma through except plasma proteins. The fluid produced by ultrafiltration is collected by the Bowman’s capsule and flows on into the proximal convoluted tubule. 11.3.7: Explain the roles of the loop of Henle, medulla, collecting duct and ADH (vasopressin) in maintaining the water balance of the blood. (pg102) Survey of Excretory Systems - Intro Various excretory mechanisms have evolved in animals for the purpose of osmoregulation and for the removal of toxins. Toxins include by-products of cellular metabolism, such as the nitrogen wastes. Contractile Vacuoles Found in the cytoplasm of various protists, such as paramecia and amoebas. These vacuoles accumulate water, merge with the plasma membrane, and release the water to the environment. Flame Cells Aka protonephridium Flatworms. Network of dead-end tubules lacking internal openings. The cells are distributed along a branched tube system that permeates the flatworm. Body fluids are filtered across the flame cells whose internal cilia move the fluids through the tube system. Wastes (water and salts) are excreted from the tubule system through pores that exit the body. Tubules reabsorb most solutes before the urine exits the body so the urine is dilute. Aka Metanephridia Unlike previous, has internal openings Earthworms. Occur in pairs within each segment of the earthworm. Interstitial fluids enter through a cilated opening called a nephrostome. Fluids concentrated as they pass through the collecting tubule which includes a storage bladder that opens to the outside through a pores. As urine moves along the tubule, most solutes are reabsorbed and returned to the blood in the capillaries. Nitrogenous wastes remain and are excreted outside. Live in damp soil and absorb water through osmosis. They balance water influx by making diluted urine. Nephridia Malpighian Tubules Insects and other terrestrial arthropods. Tubes attached to the midsection of the digestive tract collect body fluids from the hemolymph that bathe the cells. Fluids which include both nitrogen wastes and materials to be retained (salts and water), are deposited to the midsection. • As fluids pass near the rectum, most solutes are pumped back into the hemolymph. • The nitrogenous wastes are eliminated as nearly dry matter along with the feces. Kidney The last one.. Kidneys. But you all should be experts on that now. Teehee. Regulation of Kidney Functions: Hormones These hormones influence osmoregulation by regulating the concentration of salts in the urine: ADH JGA Angiotensin II Aldosterone ANF Antidiuretic Hormone (ADH) Increases the reabsorption of water by the body and increases the concentration of salts in the urine. It does this by increasing the permeability of the collecting duct to water. Urine becomes more concentrated as water diffuses out of the collecting duct as the filtrate descends into the renal pelvis. Recall its position: Posterior Pituitary Recall process of Feedback Inhibition Juxtaglomerular Apparatus (JGA) to Angiotensin II Location: near afferent arteriole that supplies blood to the glomerulus When blood pressure/volume drops, an enzyme (renin) aids in producing a peptide called angiotensin II. This hormone raises blood pressure by constricting arterioles, decreasing blood flow to many capillaries, like in the kidney. Also stimulates the proximal tubules of the nephrons to reabosorb more NaCL and water which reduces the amount of both in the urine. Aldosterone This hormone acts on the nephrons’ distal tubules making them reaborb more sodium (Na+) and water allowing for further increase of blood volume/pressure It does this by increasing the permeability of the distal tubule and collecting duct to Na+ As a result, more Na+ diffuses out of this tubule and duct allowing for water to passive flow. In summary so far, RAAS Starting basically from the JGA to Aldosterone, that whole process is called RAAS When blood pressure drops, JGA is released and aids in rising it again with angiotensin II and aldosterone. So, the first hormone ADH and the RAAS process raise blood pressure. Isn’t this a bit redundant? ADH vs RAAS Both increase water reabsorption, but counter different osmoregulatory proglems. ADH is a response to body dehydration. A loss of both salt and body fluids such as an injury or severe diarrhea will reduce blood volume without increasing osmolarity. This will not induce a change in ADH release but RAAS will respond by increasing water and Na+ reabsorption. Atrial Natriuretic Factor (ANF) This hormone opposes the former RAAS Recall renin, the enzyme that helped make JGA ANG inhibits the release of renin, inhibits NaCl reabsorption by the collecting ducts, and reduces aldosterone release. This basically lowers blood volume/pressure. Thus, ADH, RAAS, and ANF is basically a biological check and balance system Guess what?! No more new info! Review if time. Enjoy your 3 day weekend! =] Study away for those exams….=/