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Phys Exam 4: Ch 27

Tubular Processing of the Glomerular filtrate

QuestionAnswer
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
Created by: hclark86