Homeostasis in the urinary system

Function-maintenance of homeostasis a. Regulation of water content in the blood In the case of dehydration, sensors in the brain stimulate the release of the hormone ADH (antidiuretic hormone also called vasopressin) ADH is released from the pituitary It passes through the blood to the kidneys where it stimulates the release of water back into the blood from the distal tubule and the collecting duct. When water balance is normal, the ADH secretion is stopped. Chapter 30

Chapter 30

Penicillin, salicylates (aspirin) excreted b. Regulation of levels of molecules in the blood Penicillin, salicylates (aspirin) excreted glucose, proteins, and amino acids are all reabsorbed. phosphate, sulfate, lactate, vit. C all reabsorbed. Chapter 30

Most important buffer system is bicarbonate ion (HCO3- ) c. Maintenance of blood pH Most important buffer system is bicarbonate ion (HCO3- ) buffers maintain constant pH kidney reabsorbs bicarbonate when blood is acidic and produces bicarbonate to further buffer the blood. Chapter 30

d. Regulation of blood pressure and oxygen content when blood pressure falls, kidneys release renin into the blood. This causes formation of angiotensin. angiotensin causes arterioles to constrict increasing blood pressure. Constriction also causes less blood to be filtered, maintaining water balance and further increasing blood pressure. for low oxygen levels, kidneys release erythropoietin, stimulating red blood cell growth Chapter 30

Cross Section of a Kidney Biology: Life on Earth (Audesirk) Renal Pelvis Renal Cortex Cross Section of a Kidney Renal Artery Nephron Renal Medulla Renal Vein Renal Pelvis The cross section shows the blood supply and internal structure of a kidney. The renal artery, which brings blood to the kidney, and the renal vein, which carries the filtered blood away, branch extensively within the kidney. The two are joined by a highly permeable capillary network through which substances are exchanged between the blood and the nephrons. A nephron, considerably enlarged, is drawn to show its orientation in the kidney. The renal pelvis is the branched collecting chamber that funnels urine out of the kidney. Ureter Chapter 30 Chapter 30

Regulation of Water in Blood Biology: Life on Earth (Audesirk) Regulation of Water in Blood Sensors in hypothalamus gauge osmotic concentration Deviations cause posterior pituitary to turn ADH release on or off ADH restores blood osmotic concentration Red = increased osmotic concentration Green = decreased osmotic concentration 1 5 2 The water content of the blood is regulated in part by a negative feedback mechanism. Sensors in the hypothalamus gauge the concentration of solutes in the blood; deviations from a set point cause the anterior pituitary gland to turn on or turn off a release of the hormone ADH. Any perturbation of the system (for example, by dehydration) triggers a change that will restore blood solute concentration to the appropriate level (red arrows indicate increased osmotic concentration; green arrows indicate decreased concentration). 3 4 Chapter 30 Chapter 30