TREATMENT GROUPSWaterColaCaffeine-free Diet ColaDiet ColaPotato ChipsControlFluid & Electrolyte BalanceHuman Renal PhysiologyPreparationEquipment RequiredExercise 1: Physical Analysis of UrineProcedureExercise 2: Chemical Analysis of UrineProcedureExercise 3: Excretion Analysis: Fluid and Electrolyte BalanceProcedureClean UpData AnalysisQuestionsObservation Normal Value Student Urine SpecimenColor Pale Yellow ____________________Fluid & Electrolyte BalanceHuman Renal Physiology Overview The mammalian kidney plays a major role in waste excretion and in the maintenance of extracellular water and electrolyte balance. Human beings, like other osmoregulators, must maintain their cells in osmotic and ionic conditions that are within acceptable limits. Changes in interstitial fluid composition and volume are detected and corrected, mainly through feedback control mechanisms. The control of water retention by the human kidney is a well-known example of one of these feedback mechanisms. When a large volume of water is lost from the body, dehydration can occur. Unless the lost water is replaced through ingestion of water, plasma osmolarity will increase. Changes in plasma osmolarity are sensed by osmotically- sensitive neurons located in the hypothalamus. These neurons respond to increased plasma osmolarity by increasingthe rate at which they fire. The impulses are carried down the axons of these cells to terminals located in the posterior lobe of the pituitary gland. The result is ADH, Antidiuretic Hormone, which is released into the circulatory system. ADH travels through the blood and eventually finds its way to the epithelial cells that make up the walls of the kidney’s collecting ducts. As ADH levels increase in the blood, the walls of the collecting duct become more permeable to water and thus more water is drawn out of the urine. As a result, the body retains more water and a concentrated urine is created. Water conserved by ADH re-enters the circulatory system through the capillary network that surrounds the entire tubular system of the kidney. Plasma osmolarity decreases as a result of the reabsorbed water, which dilutes solute in the blood. Eventually, the lower plasma osmolarity is sensed by the neurons in the hypothalamus and the firing rate of these cells decrease. As a result, secretion of ADH decreases and the permeability of the collecting duct to water is reduced. Feedback regulation of blood osmolarity by action of ADH Another feedback mechanism involves the synthesis and release of Aldosterone, a steroid hormone produced by the adrenal cortex in response to increased extracellular potassium (low extracellular Na+). Release of Aldosterone results in sodium reabsorbtion in the distal convoluted tubule (DCT) and the collecting ducts of the mammalian kidney. As sodium is reabsorbed from the kidney tubule, extracellular osmolarity increases (sodium is the main extracellular ion in human interstitial fluid). Eventually, extracellular osmolarity reaches a value that inhibits further release of Aldosterone. In the absence of Aldosterone, sodium is permitted to pass through the DCT/collecting ducts and finally is excreted in the urine.The following lab exercise is designed to illustrate the nature of fluid and electrolyte balance in the human kidney. You will perform a urinalysis to determine the composition, volume and osmolarity of your own urine. Then you will be asked to ingest a treatment (fluid(s) and/or solid food item(s)) and to determine the effect of the treatment on your urine volume and osmolarity over time. Preparation1. Do not drink anything but water during the 2-hour period before lab. You may drink as much water as you wish. 2. Urinate one hour before coming to lab. Do not urinate again until the first collection at the beginning of laboratory. 3. If you have circulatory problems, poor kidney function or have any medical condition related to diet, please inform your TA before the lab. Equipment RequiredDrinking cupUrine collecting cupsTest tubeTest tube rackPipettesRefractometerChemsticksExercise 1: Physical Analysis of UrineGoal: Measure the volume and specific gravity (relative solute concentration) of a urine sample. Procedure1. Retrieve a graduated specimen cup and a glass test tube. Label both the cup and test tube with tape and a marker (do NOT mark directly on the test tube or beaker!!!). Place your test tube in the test tube rack on your benchtop.2. Take the graduated specimen cup to the bathroom. Clear your bladder by urinating into the specimen cup. Return to lab with the cup half filled (you may dispose of the rest of your urine in the bathroom (toilet) after approximating the total volume of urine produced).3. In your laboratory notebook, record the time when this collection was made.4. Record the total volume of urine collected (in milliliters) as well as the color (light yellow to amber), odor and transparency (transparent to cloudy). 5. Use a plastic pipette to transfer a sample of your urine into a test tube (the test tube should be ¾ filled). Leave your specimen cup on the benchtop (in a location that minimizes the possibility of spillage) and take the sample of urine to the front of the room to determine specific gravity. You will be using a Refractometer to determine the specific gravity of your urine. A Refractometer is an instrument that measures the relative concentration of solutions as compared to distilled water (note: distilled water should not have dissolved solutes. Its specific gravity should be 1.000 (no units)). If you do not haveexperience working with a Refractometer, your TA will assist you. 6. Do not dispose of your urine until you have completed Exercise 2!Exercise 2: Chemical Analysis of UrineGoal: Use a diagnostic tool (Chemstick) to measure for the presence of: leukocytes (white blood cells), erythrocytes (red blood cells), nitrites, proteins, glucose, ketones, urobilinogen, and bilirubin (not necessarily in that order). You will also determine the urine pH. Procedure1. Bring your lab notebook, a pen and a sample of your urine (in your labeled test tube) to the front of the classroom to perform a chemical analysis of your urine. 2. Use a pipette to drop urine onto the Chemstick reagent areas (colored squares). A few drops should be sufficient to wet all reagent areas.3. Place the Chemstick on a paper towel while analyzing your results. 4. Use the indicator key on the Chemstick box to