7.6: Water Balance • Antidiuretic hormone (ADH): causes the kidneys to increase water reabsorption • Regulating ADH: • water intake • [blood solute] • blood osmotic pressure and is sensed by osmoreceptors in the hypothalamus • hypothalamus cells shrink; nerve message is sent to the pituitary gland to release ADH; initiates sensation of thirst • ADH is carried to the kidneys and signals the reabsorption of water • This produces a more concentrated urine
Osmotic Pressure (H2O balance – Regulating ADH) • high osmotic pressure = when there is little water in blood (dehydrated) … this causes water to rush out of cells to enter bloodstream. • A hormone, antidiuretic hormone (ADH), helps regulate the osmotic pressure of bodily fluids by causing the kidneys to increase water reabsorption
Animation: Hormonal Communication Communication between hypothalamus and pituitary gland. * ADH secretion triggers reabsorption of water at the kidney.
Kidneys and Blood Pressure 1. low blood volume and low blood pressure 2. sensed by blood pressure receptors in juxtaglomerular apparatus 3. renin is released to convert angiotensinogen into angiotensin 4. angiotensin constricts blood vessels and simulates release of aldosterone from adrenal gland 5. aldosterone is carried to the kidneys 6. nephrons increase Na+ and H2O reabsorption
Blood Pressure (Adjusting Blood Volume) • a hormone aldosterone, produced in the adrenal glands (located above kidneys), acts on the nephrons to increase Na+ reabsorption. • water = blood pressure = O2 to tissues so… • receptors near glomerulus detect blood pressure change • = release renin (enzyme) which converts the plasma protein angiotensinogen into angiotensin (enzyme) • * angiotensin has 2 roles: • vasoconstriction (constriction of blood vessels) • stimulates the release of aldosterone which increases reabsorption of NaCl/H2O at the nephron • in blood pressure
pH Balance • The pH of our body is 7.3 7.5 • Cell respiration releases H+ ions into the blood which decreases pH • So… our buffer system: • H+ + HCO3- H2CO3 H2O + CO2 • But this removes HCO3- ions so we have to get more of them • So… 2 things happen (in different parts of the kidney) to replace the HCO3-
Kidney Disease Diabetes Insipidus • kidneys don't concentrate urine well Symptoms • frequent urination • strong thirst response Causes • inadequate production of ________. • may be caused by head injury or brain tumours. • Medication containing lithium Treatment: • drink large volumes of water
Diabetes Mellitus • islet cells of the pancreas produce little or no insulin Symptoms • frequent urination • extreme thirst • lack of energy • vision problems Treatment • insulin replacement therapy • oral hypoglycemic medication Blood Sugar Animation: Blood Sugar Regulation in Diabetics
Bright's Disease (Nephritis) • grouping of diseases characterized by the inflammation of the nephrons. One type of nephritis changes the permeability of the glomerulus allowing proteins to pass into the nephron. This causes an increase in urine production. Kidney Stones • caused by the precipitation of mineral solutes from the blood • sharp stones can damage tissues • Extracorporeal shock-wave lithotripsy (ESWL) breaks stones into smaller fragments that can be voided through the excretory system
Dialysis Technology • the exchange of substances across a semipermeable membrane • haeomodialysis a tube is connected to a vein and blood is removed from the body the blood goes into a dialysis machine (in the tube) and passes through various environments(solutions) that remove toxins from the blood essentially a “man made” kidney.
peritoneal dialysis pump dialysis fluids into abdominal cavity (~2 L) • the selectively permeable membranes of the cavity allow toxins to go into the fluid • fluid is removed and new fluid pumped in • wastes diffuse from the plasma into the peritoneum and is filtered into the dialysis fluid • accumulated wastes are drained off and replaced several times a day • performed at home (2-6 hours) • neither provide the hormones that kidneys do so they have to be injected
Kidney Transplant • 85 % successful • new kidney is placed lower in the pelvis and attached to blood vessels and ureter • old kidney is not removed • patient must receive immunosuppressant drugs forever • Section 7.7, pp. 362, #1-10 • Review: pp. 367, #1-8; pp. 368, #1-13, 15, 17