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47 Cards in this Set
- Front
- Back
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What happens to the osmotic pressure of tubular fluid in the proximal tubules?
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remains the same. water and salts are being reabsorbed together.
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What happens to the osmotic pressure of tubular fluid in the ascending Loop of Henle?
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is becomes more diluted (less concentrated) as solute moves out. this part is impermeable to water and is not affected by ADH
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ADH acts on what part of the nephron?
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late distal tubule and collecting duct
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At what part of the nephron is the tubular fluid the most concentrated?
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bottom of the Loop of Henle and right before excretion from the collecting duct after ADH acts
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Without ADH, what happens to the osmolarity of the tubular fluid in the collecting duct?
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is becomes less concentrated as solute moves out of the collecting duct. if there was ADH, it would move water out faster than the solute and
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Obligatory urine volume =
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(minimum solute excreted)/(urine concentrating ability) = 600/1200 = 0.5 L/day
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2 major requirements to excrete a non-dilute urine
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high medullary osmotic pressure and ADH
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High specific gravity of urine suggests what endocrine disorder?
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SIADH (very concentrated urine)
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What is the difference between specific gravity and osmolarity?
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specific gravity accounts for number and size of solutes in fluid. osmolarity just accounts for number of solutes in fluid
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Why does the renal medulla need to have a high osmotic pressure?
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so when ADH inserts aquaporins in the collecting duct, the water will move out of the collecting duct towards the renal medulla
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What ensures that the renal medulla will keep a high osmotic pressure for ADH to function?
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counter-current exchange mechanism and vasa recta
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In what parts of the nephron are sodium actively transported out of tubular fluid the most?
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proximal tubule and ascending loop (some active transport in distal and collecting duct)
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What parts of the nephron are permeable to water?
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proximal tubule and descending loop. distal and CD are permeable only with ADH. ascending loop is impermeable to water
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What parts of the nephron have passive reabsorption of Na?
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proximal tubule and descending loop. and thin ascending loop
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Where is Urea reabsorbed in the nephron?
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proximal tubule, thin descending/ascending limb. collecting duct also with ADH
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What part of the nephron is most important in creating the hyper-osmotic renal medulla interstitium?
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thick ascending loop. it is impermeable to water and actively pumping the salts into the interstitial space
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How is urea reabsorbed out of the nephron tubules?
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passively
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With high ADH levels, what happens to urea in the collecting duct?
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water gets reabsorbed first and urea gets very concentrated in the tubulra fluid and eventually just diffuses into the renal interstitium. ADH also activates passive urea transporters. the final urine has a high urea concentration still though because more water moves out
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In a normal patient, what happens to the urea that is reabsorbed in the collecting duct?
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recycled through the loop of Henle to continuously contribute to the renal interstitium hyperosmolarity
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If a patient has a decreased GFR due to nephropathy, what would we expect their urea excretion rate to be?
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same. as less urea is filtered, the higher concentration of urea in the blood will force it to be filtered back to normal
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Even though urea is absorbed in the proximal tubule, why does [urea] actually increase?
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water is reabsorbed faster, concentrating the urea
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Function of the vasa recta
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provide blood supply to the renal medulla while preserving the hypoerosmolarity
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An angina patient has been taking many vasodilators. What might we expect to see with regard to his urine's specific gravity?
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vasodilators = more blood flow to renal medulla = more solute "wash out" = lower renal medulla osmolarity = less movement of water out of collecting duct = more dilute urine = lower specific gravity
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Increased medullary blood flow has what effect on urine concentration?
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more blood flow to the renal medulla = solute "wash out" = less ability to concentrate urine = dilute urine
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An angina patient has been taking many vasodilators. What might we expect to see with regard to his urine's specific gravity?
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vasodilators = more blood flow to renal medulla = more solute "wash out" = lower renal medulla osmolarity = less movement of water out of collecting duct = more dilute urine = lower specific gravity
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Increased medullary blood flow has what effect on urine concentration?
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more blood flow to the renal medulla = solute "wash out" = less ability to concentrate urine = dilute urine
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A patient has dehydration, but low sodium intake as well. What can we predict to see in his urine regarding concentration and content?
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there will be lower amounts of Na due to renin-angiotensin activation and the urine will be concentrated with other solutes. the urine will not be dilute because ADH will act to bring water in since he is dehydrated
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A patient with kidney failure has an inability to create a counter-current exchange in their nephrons. What might we expect to see when looking at specific gravity in a urinalysis?
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low specific gravity due to dilute urine. bad counter-current exchange = not very concentrated renal medulla = less water will move out of the collecting ducts when ADH acts = more water lost as urine= lower specific gravity
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A patient presents with extremely frequent urination. Desmopressin is given and the problem does not resolve. What physiologic process is most likely damaged?
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decreased ability of the V2 receptors in the nephron to respond to ADH or decreased countercurrent exchange ability
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How does an increase in extracellular osmolarity lead to ADH release?
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high blood osmolarity = shrinkage of anterior hypothalamus osmoreceptors = activation of supraoptic nuclei = ADH production/secretion > negative feedback
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What type of neurons synthesize ADH in the supraoptic nuclei?
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magnocellular
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How is ADH released from the posterior pituitary?
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calcium mediated vesicle exocytosis (its released from the neuron ending)
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What is the AV3V region?
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anteroventral region of 3rd ventricle: contains subfornical. organum vasculosum and median pre-optic nucleus that also regulate ADH secretion and osmolarity
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Excessive stimulation of the AV3V region in a patient will lead to what endocrine disorder?
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SIADH. AV3V stimulation causes ADH secretion
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How does a decrease in blood pressure lead to ADH secretion?
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baroreceptor reflex and cardiopulmonary reflexes to solitary nucleus
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ADH is more responsive to changes in (blood pressure or osmolarity)?
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osmolarity. a small change in osmolarity leads to a dramatic ADH increase.
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A patient in the ER has overdosed on morphine. What endocrine disorder could this mimic?
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SIADH. morphine leads to ADH release
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A patient in the ER has overdosed on alcohol. What endocrine disorder could this mimic?
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diabetes insipidus. alcohol inhibits ADH
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Hypoxia has what effect on ADH release?
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hypoxia = more ADH release
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Increased osmolarity of the CSF is likely detected by ...
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organum vasculosum of the lamina terminalis near AV3V
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Angiotensin 2 has what effect on thirst?
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increases thirst
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Why is "metered" fluid intake important?
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to prevent overhydration. hydration is not immediate to it is important to regulate how much we intake
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Gastrointestinal distention has what effect on thirst?
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decreases thirst
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What effect does aldosterone have on plasma sodium concentration?
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LITTLE EFFECT. aldosterone doesn't change Na CONCENTRATION that much because water follow the sodium back into the blood. it increases the amount of sodium in the blood, but concentration is almost constant. so its not that helpful to satisfy thirst
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What is Addison's disease?
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lack of aldosterone
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ADH increases levels of what urea transporter
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UT-3
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What urea transporters put urea into the renal medulla form the collecting duct?
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UT-1, UT-3
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