PGY 300 5st EditionExam # 4 Study Guide Lectures: 1 - 8Lecture 1: Physiology, the Kidney and Homeostasis Basic Functions of Renal System: Regulation of plasma osmolality (ADH) Regulation of extracellular fluid volume and blood pressure (RAAS and ANP) Maintenance of electrolyte balance – Na, K, Ca, Mg, Cl, PO43- Regulation of plasma pH by conservation of & generation of new bicarbonate Excretion of metabolic waste - urea, uric acid, creatinine Production of hormone, erythropoietin – regulates production of RBC Activation of Vitamin D – hormone regulates Ca balanceUrinary SystemNervous System – automatic Bladder & Sphincter o Sensory neuron o Sympathetic/Parasympathetic neurono Motor (somatic) neuron – controls external sphincter o Sphincters: internal (smooth m.) & external (skeletal m.)  Renal function o Sympathetic neuron Micturition: control over urination Mass Balance and the Steady-State Input = outputSolution, Solvents, Solutes, Electrolytes and Body Fluid Compartments:Total body water (TBW) and Body weight (BW) Adult : 55-60 % total body weight TBW = intracellular fluid (ICF) volume + extracellular fluid (ECF) volume o General ratio : ICF – 2/3, ECF - 1/33 Major fluid compartments: Plasma- 3.5L Interstitial – 10.5L ECF : 14L ICF: 28LStructure of the Human Nephron & Associated Vasculature:Peritubular capillaries – surround nephronLong Loop of Henle – deep into the medullaShort Loop of Henle – closer to the surface of kidneyPrincipal cell – majority of Na, Cl, H2O absorptionKidney – transporting organ GFR: glomerus filtration rate – 120-180 liters per day  Need rapid filter/reabsorption to figure out if something’s wrongLecture 2: Glomerular Filtration and Renal Blood FlowRenal arteries take blood to the renal cortexAfferent arterioles and glomeruli are all found in renal cortexOrganizations of Glomerular Filter:- Size - Electrical charge Mesangial cell: control of surface area for filtration Podocyte: foot cell, surround each capillary leaving silts for filtration Afferent and efferent arterioles are the major sites of renal vascular resistance Downstream of blood = low pressure Upstream of blood = high pressureStarling Forces of Capillary Exchange:Net pressure = hydrostatic pressure – colloid osmotic pressure (oncotic) Hydrostatic pressure: forces fluid (H2O) out of capillary  Oncotic pressure: pulls fluid in the capillary, bring H2O in vascular space- constant - presence of plasma protein Starling Forces in the Glomerulus:Kf = filtration coefficient - diabetic = low Kf- protein in urine = high KfGFR: glomerular filtration rate- GFR = Kf * PnetRelationship between arterial blood press & renal blood flow (RBF) & GFR- Built in every nephron; prevent changes in BF, BP, filtration through kidney Macula densa cells- Respond to flow & concentration rate of NaAutoregulation: Changes in arterial BP- Myogenic - Stretch of vascular smooth m. Changes in NaCl concentration of tubular fluid flowing past macula densa - Tubuloglomerular feedback (TGF)- Adenosine increases resistance of afferent arterioleLecture 3: Renal Tubular TransportThe process of reabsorption and secretion occur by unique mechanisms, characteristic to each segment of the renal tubule- Different R (reabsorption) = different mechanisms Transepithelial Solute & Water transport:- Epithelial: separate 2 fluid compartments (barriers)- Paracellular pathway: moves around cell- Transcellular pathway: moves through cell- Tight junction: can be tight or leaky; if tighter greater ability to separate fluid compartmentsConcentration of solutes in tubule fluid as a function of length along proximal tubule:- Cl-: # of negative = # of positive- Na+ osmolality: constant; reduce volume of Na & H2O therefore ratio remains same- Osmolality: measure of # of solute in solution- Proximal tubule; once nutrients leave proximal tubule not absorbed, leads to urineIsosmotic fluid reabsorption: no change in value- Leaky to waterThick ascending limb = diluting segment - Regulate independently solute & H2O movementIntercalated cells – acid secretionLecture 4: Renal ClearanceAssessment of Renal Function:- Measurement of RBF & GFR- Clearance measurements- Plasma creatinine - Blood Urea Nitrogen (BUN)Assessment of GFR: mass balance within a nephron- GFR = urine flow * Uinulin/ InulinGeneral Clearance Equation - Clearance of X (Cx) = urine flow * U x/ PxInulin Clearance – freely filtered, not reabsorbed, not secreted, and not metabolizedAssessment of “NET” Reabsorption and Secretion:- NET : cannot be certain- Net reabsorption: some returned to body- Net secretion: some added to tubular fluid excess to filtrationLecture 5: Regulation of Water Balance AKA Osmoregulation- Osmoregulation: separating water and solute movementsWater balance: measure what you have, compare what you want- If there’s a difference = error; reg. sys. Works on error back to O Osmosis and osmotic pressure:- Osmosis: diffusion of water; drive by differences in concentration of water molecules (high to low)- Must have equal pressure - Solute concentration (things dissolve in water): determines osmotic pressure- Water moves from low osmotic pressure to high osmotic pressure; water diffusing down chemical gradient- Concentration: # of particles we’re interested in per unit of volume- Increase in H2O = decrease in osmotic pressure- If not in equilibrium pressure flows to ICF -> can swell up cellsOsmoreceptors: detects plasma osmolality, thirst Antidiuretic hormone (ADH): sends vasopressin hormone down axon & stores in terminal & vesiclesBaroreceptors input: protective, “fail safe” detects BP; not going to happen unless loss of a lot of bloodAQP2: aquaporin 2 makes H2O impermeableWater diuresis- excrete H2OAntidiuresis- conserves H2OLonger Loop of Henle = greater effect on gradient Lecture 6: Regulation of Potassium Balance PNa = mmoles Na/ ECF Volume - P= plasma compartment - Mmoles Na = quantityECF Volume = mmoles Na/ PNa- ECF Volume related to quantity of Na- PNa = fixed value - Increase in ECF Volume = increase in mmoles Na; vice versaVolume & Sodium sensors:Vascular Low pressure - Cardiac atria - Pulmonary vasculature  High pressure - Carotid sinus- Aortic arch - Juxtaglomerular apparatus of kidney  CNS Hepatic – liverSegmental sodium reabsorption by nephron & collecting duct- If want to conserve or expand volume -> conserve Na- Decrease volume