7.2 Urinary Flashcards

Question

describe the extrinsic mechanisms

Answer 1

* hormonal (renin-angiotensin-aldosterone mechanism) * decrease in systemic BP, sensed by granular cells of juxtaglomerular complex of kidney * releases renin * catalyzes cascade resulting in formation of angiotensin II * Inc aldosterone secreted by adrenal cortex * inc Na reabsorption by kidney tubules; water follows * increases blood volume * overall inc in systemic pressure * neural contorls * inhibits baroreceptors in blood vessels of systemic circulation * activates sympathetic nervous system * acts on granualr cells of juxtaglomerular complex and/or vasocontriction of systemic arterioles increasesing peripheral resistance * (converges to pathway above)

Answer 2

- renal cells releae a variety of chemicals - some act as paracrine factors that affect renal arterioles like adenosine and prostaglandin E₂ - some cells make thier own locally acting angiotensin II - reinforces effects of hormonal angiotensin II

Answer 3

- abnoramlly low urinary output (less than 50mL/day) - may indicate that glomerular blood pressure is too low to cause filtration - renal failure and anuria can also result from situations in which nephrons stop functioning ex: acute nephritis, transfusion reactions, and crush injuries (injury to kidenys themselves) \*injury to the kidneys themselves

Answer 4

- quickly recalis most of tubualr contens and return them to blood - almost all organic nutrients are reabsorbed - water and ion reabsorption is partly hrmonally regualred and adjusted - includes active and passive tubular reabsorption, substances can flow **trancellularly or paracellularly**

Answer 5

1. transport across the apical membrane 2. diffusion through the cytosol 3. transport across the basolaterial membrane (ofen involved the lateral intercellular spaces bc ions transported into these spaces) 4. movement thorugh the interstitial fluid and into capillary

Answer 6

- movemnt through leaky tight junctions, particularly in PCT - movement through the interstitial fluid and into the capillary \*limited by tight junctions in move parts of tubule, but leaky in PCT water, Ca, Mg, K and some Na

Answer 7

1. Na is tranported across basolateral membrane by Na/K ATPase pump 2. K+ dissues back across the membrane passively (thu channel * K+ leaks out cell into interstitial fluid -\> neg charge inside cell * helps to pull Na inward across apical membrane * Na+ and K+ reutn into circulation via **peritubular capillaries** 3. Na reabsoprtion across apical membrane via secondary active tranposrt * coupled with other ions, amino acids, glucose and occasionally facilliated diffusion * export of Na caues an electrochemical gradietns (lots Na in filtrate, little in tubule cell) * Na reabs is main driving force for reabsorption of other nutrients

Answer 8

- constituative aquaporins in PCT (obligatorry water reabsorption) - inducible aquaporins in collecting ducts (faculative, inseted into collecting ducts only if ADH is present

Answer 9

- as water is reabsorbed, the concentration of solutes remaining in filtrate inc -\> forms concentration gradient - solutes passively follow concentration gradient (if able) - \> lipid soluble mol will diffuse directly though tubule cells - \> ions and urea follow paracellular route \*this is why lipid-solubledrugsand environmental pollutants are reabsorbed even though it is not desirable

Answer 10

1. At basolateral membrane Na is pumped into interstitial space by Na/K+ ATPase. * active Na transport creates conc gradient 2. Get downhill Na+ entry at apical membrane 3. Reabsorption of organic nutrients and certain ions by cotransport at **apical membrane** 4. reabsorption of water by osmosis via aquaporins. * inc conc of solutes that are left behind * solutes can be reabsored as they move down gradients 5. Lipid solubel substances diffuse by transcellular route 6. ions and urea diffuse by paracellular route

Answer 11

- transport maximum (T_m) exists for almost every reabsorbed substance \*reflects number of carriers in renal tubules - when carriers for a solute are saturated, excess is excreted in urine ex: hyperglycemia leads to high blood glucose levels that exceed T_m and glucose spills over into urine

Answer 12

- in PCT by primary active transport via basolateral Na+-K+ pump - crosses apical memrbane through channels, symptorters or antiporters

Answer 13

\*glucose amino acids, vitamins and some ions - secondary active transport with Na

Answer 14

passive paracellular diffusion driven by electrochemical gradient

Answer 15

HCO₃^- abs by secondary active tranpodrt in PCT linked to H+ sections and Na+ reabsorption

Answer 16

primarily passive paracellular diffusion ~50%

Answer 17

65% in PCT by osmosis (driven by solute reabsorption -\> obligatory water reabs) - in descening limb: permeable to water \*ascenidn glimb is impermeable to water

Answer 18

\*impermeable to water but permeable to solutes - thin segment: passive diffusion of Na+ - Thick segments ahs secondary active Na+/K+/2Cl sympotrts and Na/J antiporters to transport Na in \*Na, Cl and K by secondary actie transport \*Ca and Mg by passive paracellular diffusion

Answer 19

- PCT and nephron loop handle majority of reabsorption but is not responsive to changing needs of body - DCT and collecting duct do fine tuning of reabsorption

Answer 20

priamry active Na transport at basolateral membrane secondary active transport at apical membrane via Na/Cl sympotrter - aldosterone regulated at distal portion

Answer 21

- pasive uptake via PTH modulated channels in apical membrane - primary and secondary active transport in basolateral membrane

Answer 22

priamry ctive of Na (req aldosterone) - passive paracellular diffusion of some Cl - net K= sectetion

Answer 23

- faculative water reabs, ADH is required

Answer 24

- facilitated diffusion in response to conc gradient in deep medulla region - contributes to osmotic gradient

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7.2 Urinary Flashcards

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