PHIS 206 1st EditionLecture 21Outline of Last Lecture I. Functions of the KidneysII. Excretory SystemIII. NephronIV. 2 Types of NephronsV. Blood Supply VI. 3 ProcessesVII. FiltrationVIII. ReabsorptionIX. Pressure DifferenceX. Reabsorption and Active TransportOutline of Current Lecture I. GlucoseII. DiabetesIII. Active Reabsorption of Na+IV. Passive ReabsorptionV. SecretionVI. Urine OutputVII. Plasma ClearanceVIII. InulinIX. CreatinineX. p-Aminohippuric acid (PAH)Current LectureI. Glucose-100% reabsorbed for a normal person-only fuel brain can use-active transport system: all reabsorbed in proximal tubule-must have a carrier protein that is saturableThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute. input of Energy moves it outside nephron finite capacity that the protein can carry-Maximum rate: transport maximumamount entering: tubular loado concentration in glomerulal filtrate × filtration rate- Transfer Maximum: Tm (Glucose) = 400 mg/min - Normal Tubular Load = 125 mg/min 100% gets reabsorbed in proximal tubule- Plasma Glucose Level 1 min 125 mg/min 0 in urine 2 min 250 mg/min 0 in urine 3 min 375 mg/min 0 in urine 4 min 500 mg/min 100 in urine 5 min 625 mg/min 225 in urine 6 min 750 mg/min 350 in urineII. Diabetes-Diabetes melatis: “honeylike”-Diabetes insipitis: “without sugar”III. Active Reabsorption of Na+-causes passive reabsorption of Cl- since cation (of Na+) and anion (of Cl-) must equal out-When Na+ and Cl- reabsorbed, water follows osmoticallyIV. Passive Reabsorption-things can diffuse out of nephron passively best example: urea (non-toxic)-most aquatic animals produce ammonia that diffuse away fast before storage we have to convert toxic ammonia to something safer convert ammonia into urea-urea is 2nd fastest to diffuse, after water-osmotically reabsorb water, as water decreases, urea increases urea diffuses up when left in high concentrations-sequence of events1. Actively transport solutes2. Water follows (PASSIVE)3. Things that can diffuse (urea) will diffuse down conc. gradient (PASSIVE)-urea more in plasmagreater than Tm = 400 mg/minV. Secretion-add stuff to tubule add Extracellular Fluid in tubules, which is plasma in capillaries-actively transfer into nephron from capillaries-MOST IMPORTANT THING SECRETED: H+ proximal, distal, collecting vessel-Number of anions actively secreted too-Anionated groups attach to drugs and are excreted through urineVI. Urine Output-1-2 L/day: normal urine output ≈ 1 mL/min-Gfr = 180 L/day-urine output = 1 L/day VII. Plasma Clearance-know how much you are excreting and concentration of stuff in plasma, then you know the number of mL of plasma to provide some specific compound each minute (Definition of Plasma Clearance)-plasma clearance tells you how efficiently you are removing the compound from the kidneys-plasma clearance large to provide stuff that is actively secretedVIII. Inulin-freely-filtered, but not reabsorbed or secreted-amount in glomerulal filtrate is amount that entered-if you measure inulin clearance, you are actually measuring the Gfr-not normal in blood unless you love garlic or artichokesIX. Creatinine-creatinine clearance also gives you Gfr-not reabsorbed, weakly secreted-more commonly-used to measure GfrX. p-Aminohippuric acid (PAH)-actively-secreted so almost none left in renal vein-whatever enters winds up in urine mainly-plasma clearance for PAH = renal plasma flow-renal blood flow is approximately 2× plasma flowReabsorbed 179
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