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Phys Exam 4: Ch 27
Tubular Processing of the Glomerular filtrate
Question | Answer |
---|---|
Define Excretion | Filtration - Resorption + Secretion |
How do you calculate filtration rate? | FR = [plasma] x GFR |
What is the average daily value for GFR | 180 L/day |
What 2 substances are completely reabsorbed? | Glucose, AAs |
What 3 substances that are almost completely reabsorbed? | Bicarb ions, Na+, Cl- |
What substance is not reabsorbed at all? | Creatinine |
Which is larger, filtration & resorption, or excretion? | Filtration & reabsorption |
Is absorption very selective or less selective? | Very selective, esp in contrast to filtration |
Refresh: active transport | moves a solute against an electrochemical gradient and requires energy derived from metabolism (ATP) |
Refresh: primary active transport | liked directly to cellular hydrolysis of ATP |
Refresh: secondary active transport | Utilized (but is not directly linked to) ATP hydrolysis |
Refresh: osmosis | movement of water in the direction of ion transport |
Refresh: passive diffusion | Cl- and urea move down gradients set up by osmosis |
Refresh: transcellular movement of molecules | passage through a tubular cell |
Refresh: paracellular movement of molecules | passage between tubular cells across tight jxns |
What causes transport maximum? | Due to saturation of proteins involved in active transport |
What is the normal glucose filtration rate? | 125 mb/min |
What is normal plasma [glucose]? | below 200mg/100mL |
What happens if plasma [glucose] is above normal? | If levels are above 200mg/100mL some glucose appears in the urine. Some nephrons below average value |
Describe cells in the proximal tubule | Abundant mitochondria, extensive surface area (brush border, basal channels), high carrier [protein] |
What gets reabsorbed in the proximal tubule? | ~65% of the filtered Na+, Cl-, HCO3-, K+, and all glucose & AAs |
How does the proximal tubule neutralize HCO3-? | Secretion of H+ neutralized HCO3- to water and CO2 via the Na-H antiporter |
What substances are secreted by the proximal tubular cells and are not reabsorbed? | Organic acids & bases, oxalate, catecholamines, salicylates, penicillin |
How is Cl- resorption enhanced? | Na+ resorption increases lumen negativity |
What increases [Cl-]? | Osmotic removal of water |
What is ionically co-transported w/Cl-? | Na+ |
What maintains a low intracellular [Na+]? | Na-K-ATPase pump in the basolateral membrane |
What carries in most of the Na+? | The 1-Na, 2-Cl, 1-K co-transporter on the apical surface |
What is the fxn of the Na-H counter-transport? | Moving Na+ into the cell from the luminal side |
What is the fxn of principal cells? | Reabsorb Na, secrete K, using the Na-K-ATPase pump |
What is the effects of the presence of aldosterone on the principal cells? | Increases the concentration of the Na-K-ATPase pumps, and the specific Na-channel proteins by inducing synthesis of these pumps |
What does ADH do to the permeability of the late distal tubule and cortical collecting tubule? | The tubule & duct are impervious to water except in the presence of ADH |
Where are principal cells found? | The late distal tubule & cortical collecting tubule |
What is the fxn of intercalated cells and where are they found? | Reabsorb HCO3- & K+, secrete H+, are found in the late distal tubule and cortical collecting tubule |
How is H+ secreted in the late distal tubule and cortical collecting tubule? | H+-ATPase pump |
What is the fxn of the medullary collecting duct? | Location of final fine-tuning of Na+ & water excretion |
What happens to urea in the medullary collecting ducts? | Urea is reabsorbed into the interstitial fluid of the medulla, raising osmolality |
What happens to H+ in the medullary collecting ducts? | secreted against a large concentration gradient using H+-ATPase pump |
What controls water permeability of the medullary collecting ducts? | Vasopressin (ADH) |
How does an increased renal arterial pressure cause an increase in urine output? | Slight increase in GFR, increase in peritubular capillary hydrostatic pressure, and reduction in AngII production |
How does AndII influence urine output? | |
How does aldosterone influence urine output? | |
How does ADH/vasopressin influence urine output? | Increases water permeability of the late distal tubule and collecting duct. Stimulates movement of aquaporin to the cell membrane, and several aquaporin proteins fuse to form a water channel |
What is glomerulotubular balance? | The resorption rate of the proximal tubule increases in response too increased flow/increased GFR |
What happens in the presence of ADH? | Water is reabsorbed back into the body, decreasing the amount of urine |
What happens in the absence of ADH? | Water is excreted, increasing the amount of urine |
When are ANP & BNP (atrial natriuretic peptide) secreted, and what do they do? | |
How does parathyroid hormone (PTH) influence urine output? | |
What are the 4 parts of the renal tubule? | Proximal tubule, Loop of Henle, Distal tubule, Collecting tubule |
What are the 3 parts of the Loop of Henle? | Thin descending, Thin & Thick ascending |
What are the 2 parts of the distal tubule? | early & late distal tubule |
What are the 2 parts of the collecting tubule? | cortical collecting tubule, medullary collecting tubule |