Urine Formation  Glomerular filtrate: is the plasma like fluid that is squeezed from the glomerulus and is collected by the bowman’s capsule  Glomerular filtration rate (GFR): can be auto regulated using BP in vessels, flow of tubular fluid, the enzyme renin

Urine Formation  Renin: an enzyme that is produced when BP is low, changes a protein into the hormone angiotensin II  angiotensin II: slows GFR to reduce water loss, promotes Na and water retention

Urine Formation  PCT: reabsorbs 65% of filtrate through passive and active transport  Na + : is key b/c of osmotic gradient  Cl -, HCO 3, glucose, are also reabsorbed  The nephron reabsorbs 40-60% of urea but due to the reabsorption of 99% water the concentration of urea is much higher  Of 180L filtrate only 2-3L voided

Formation Hormones  Aldosterone: the salt hormone increases the nephron loop uptake of Na + which in turn increases K + and Cl - uptake  Atrial natriuretic peptide (ANP): is secreted when BP is high causes a decrease in water and Na + uptake reducing B volume  Antiduretic hormone (ADH): dehydration trigger, causes increase in water uptake in PCT  Parathyroid (PTH): restores Ca 2+ levels

Water conservation  Countercurrent multiplier: occurs in the loop. The thin descending part diffuses water out to ECF based on osmolarity, the thick ascending part actively transports salt and K + in response to increased levels of salt and K +  Countercurrent exchange: B vessels loose water due to osmolarity and then on the way up gain more water then they lost