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Flashcards in 9.6 Urine Deck (21):

What are the ascending and descending limb of the loop of Henle permeable to?

Descending limb is permeable to water, water leaves and filtrate becomes concentrated inside the loop of Henle
Ascending limb is NOT permeable water, pumps out NaCl without allowing water to balance


What is the vasa recta? What is it's function?

countercurrent exchange: vasa recta blood flow turns up and around the loops of henle, exchanging NaCl and water along with the established gradient
= maintain countercurrent


How does ADH work on the nephron?

More ADH-> more aquaporin channels in collecting duct-> more water retained


How do diuretics work?

prescribed for high blood pressure, block hormonal mechanisms, block medullary gradient formation, dilute, large volumes of urine excreted


What is tubular secretion?

selectively adding to the filtrate by removing molecules from the blood
Excess in blood, needs excretion: metabolic waste (creatinine, etc), plasma protein bound drugs, acid (H+) or base (HCO3-), ions (K+), urea


Where is K+ secreted? Why is this important?

is regulated to maintain electrical gradients, especially in the heart, and maintain Na/K pump activity in the kidneys
Secretion occurs in the DCT and Collecting Duct
Na/K Pump, moves K+ into tubules
K+ leaky channels in DCT and collecting duct lumen
Secretion stimulated by aldosterone


Where is H+ secreted? Why important?

H+ secretion is regulated in order to maintain acid/base balance
Normally causes urine to be acidic pH = 6
occurs in mainly in PCT and Collecting Duct
H+ ATPase pumps
H+/K+ ATPase pumps
Na+/H+ cotransporters; antiporters
Balanced with HCO3- formation and reabsorption to blood


What are sources of acid?

phosphoric acid: due to protein breakdown
lactic acid: due to anaerobic metabolism
ketone bodies: due to fatty acid metabolism (lack of glucose energy source)
CO2 production


What is the timeframe for respiratory vs urinary compensation to acid?

respiratory compensation within seconds
urinary compensation within hours to days


How are organic ions secreted? Consequences?

Two types of non-selective carriers for
organic anions
organic cations
Consequence of general anion/cation group carriers is that drugs compete for carriers during elimination, causes drug interactions
Two drugs taken that use the same carrier, will NOT be fully eliminated


What determines the plasma clearance rate of something?

Reabsorption rate
Secretion rate


Compare creatine, glucose, and H+ clearance to GFR

Creatinine- normal breakdown product, usually 100% cleared, so creatinine clearance rate is a good estimate of GFR
Vs Glucose- filtered, should be 100% reabsorbed: glucose < GFR, should be 0
Acid- filtered, actively removed, clearance rate should be much higher than GFR


How can creatinine clearance be used to estimate GFR?

fully filtered, not reabsorbed 100% produced creatinine should be found in urine (and very little in the blood)
simple way to estimate GFR
low creatinine clearance  low GFR, impaired renal function, hypotension, heart failure, shock
high creatinine clearance  high creatinine production ex: pregnancy, diabetes mellitus, high protein diet


What regulate Na+ reabsorption and secretion?

Renin-angiotensin-Aldosterone System (RAAS)
Increases Na+ reabsorption
Atrial and Brain Natriuretic Peptides: ANP & BNP
Decreases Na+ reabsorption


What regulates water reabsorption and secretion?

Osmotic Gradient & Vasopressin (ADH)
Increases H20 reabsorption, maintains blood volume


What is the net effect of the RAAS pathway?

is increased Na+ reabsorption in DCT and Collecting Duct
= BP up


What cell secretes renin? Stimulus?

JG cells secrete renin, stimulated by JGA (stimulus: low BP)


What is the RAAS pathway?

Renin convertes angiotensinogen into angiotensin I
Angiotensin I converted to angiotensin II by ACE in lung
Angiotensin II stimulates adrenal cortex: increase thirst, systemic vasoconstriction; aldosterone release


What are the stimulus, integration, and response of the thirst response?

stimulus: low ECF, dry mouth, angiotensin II
angiotensin II released by RAAS pathway during low blood pressure
integration: hypothalamus
response: thirst, water seeking behavior


What are the stimulus, integration, and response of ADH release?

stimulus: low blood volume
integration: hypothalamus to posterior pituitary
produce and release ADH
response: increases water reabsorption by kidneys (collecting duct)
increases blood volume
reduces urine output


What are ANP, BNP?
Fxn? Stimulus?

are released by the atria and ventricles to lower blood volume and blood pressure
Decreases Na+ reabsorption in DCT and Collecting Duct
inhibits renin, inhibit aldosterone, inhibit vasopressin
Relax mesangial cells to decrease Kf
Triggered by:
Heart muscle stretch due to increased blood volume