Exam 4 Part 2 Flashcards
What are the 2 main functions of the loop of Henle?
reabsorbs H2O then reabsorbsNaCl
The end goal of the Loop of Henle is create a _____tonic tubule fluid
hypotonic
What is the main action of the thin descending limb?
H2O reabsorption
Does NaCl reabsorption occur in the thin descending limb?
no
Fluid movement down the thin descending limb become more ___________
concentrated (hyperosmotic)
What is the main action of the thin ascending limb/thick ascending?
NaCl reabsorption
Does H2O reabsorption occur in the thin acsending limb/thick ascending?
no
Fluid movement up the thin ascending limb/thick ascending limb become more ___________
diluted (hyposmotic)
How does reabsorption of NaCl through the thin ascending limb occur?
passivley
How does reabsorption of NaCl through the thick ascending limb occur?
active transport
What active transporter reabsorbs NaCl out of the thick ascending limb?
Na/K/2Cl co-transporter
What is the Vte in the thick ascending limb?
+10
very positive
What makes the Vte so positive in the thick ascending limb?
abundance of apical K+ channel that stimualtes paracellular transport of K+ into tubule lumen
What is Bartter Syndrome?
defective Na/K/Cl cotransporter (thick ascending limb) causing less K+ movement = less positive Vte = slows ion reabsorption
What happens to the Vte if the Na/K/Cl cotransporter in the thick ascending limb is non-functional?
less K+ movement = less positive Vte = slows ion reabsorption
What are loop diuretics?
inhibit Na/K/Cl cotransporter (in thick ascending limb)
reduces NaCl reabsorption by preventing K+ for keeping lumen positive
What is the importance of K+ in the thick ascending limb?
keeps Vte positive to drive ion reabsorption
What ions are reabsorbed in the thick ascending limb?
Na+
Cl-
Ca2+
Mg2+
How is K+ reabsorbed in the thick ascending limb?
50% via Na/K/Cl cotransporter (transcellular)
How is Ca2+ reabsorbed in the thick ascending limb?
50% paracellular
50% transcellular
- has its own ion channel, does not use Na/K/Cl cotransporter
What ion’s reabsorption dominates of Ca2+ through the paracellular route?
Mg2+
How is Mg2+ reabsorbed in the thick ascending limb?
paracellular diffusion
Where is most of the Mg2+ reabsorbed?
thick ascending limb (70%)
______________-1 is required for Mg2+ diffusion through tight junctions and is the reason for high Mg2+ in the TAL
paracellin-1
What are the 2 cell types in the distal tubule and collective duct?
alpha/beta-intercalated cells
principle cells
What is the importance of principle cells in the distal tubule?
Na+ reabsorption stimulated by aldosterone
What is special about the medullary collecting duct cells?
(end of nephron)
very tight to prevent reabsorption/leaking at the end
In the distal tubule, NaCl is reabsorbed transcellularly via what co-transporter?
thiazide sensitive NaCl cotransporter
What happens if the thiazide sensitive NaCl cotransporter in the distal tubule doesn’t work?
NaCl is not reabsorbed and urine is more concentrated
What is Gitelman syndrome?
defective thiazide sensitive NaCl cotransporter in the distal tubule (NaCl not reabsorbed)
What is the Vte of principle cells in the collect duct?
-40 mV
very negative
What is the transcellular transporter/channel that reabsorbs Na+ in principle cells of the collecting duct?
ENac
Why is the Vte of principle cells so negative?
ENac is pulling Na+ out of lumen
How does Cl- travel out of lumen in collecting duct in principle cells?
paracellularly
What it Liddle syndrome?
increased ENac activity (collecting duct) causing high BP
- increased reabsorption of NaCl
What is the Vte of beta-intercalated cells in the collecting duct?
-40 mV
very negative
Why is the Vte of beta-intercalated cells so negative in the collecting ducts?
HCO3- is being pumped into lumen
What transporter is used by beta-intercalated cells in collecting ducts to transport Cl-?
Cl-HCO3- exchanger
Do beta-intercalated cells in the collecting duct transport Na+?
no
only Cl-, HCO3, H+
What is special about the beta-intercalated in the collecting duct?
aid in acid base exchange
(HCO3 into the lumen and H+ reabsorbed)
What is aldosterone’s affect on NaCl reabsorption?
increases NaCl reabsorption
Do intercalated cells or principle cells in the collecting duct perform K+ secretion?
principle cells
What cells perform K+ reabsorption in DT and CD?
alpha-intercalated cells
Why does hypokalemia induce acidosis?
K+ reabsorption is mediated by lumen H/K pump where H+ is secreted
- low K+ in blood = higher H+ in blood
- alpha-intercalated cells
Do alpha or beta intercalated cells perform H+ secretion?
alpha
Do alpha or beta intercalated cells perform HCO3- secretion?
beta
What side is the HCO3- pump and the H+ pump located on alpha-intercalated cells?
HCO3-: basolateral
H+: apical
What side is the HCO3- pump and the H+ pump located on beta-intercalated cells?
HCO3-: apical
H+: basolateral
Ca+ is reabsorbed in the proximal tubule but also in the …
distal (convoluted) tubule
Ca+ reabsorption is tightly regulated in the __________ compared to the proximal tubule.
distal (convoluted) tubule
What are volatile vs non-volatile acid?
volatile: blown off by lungs
non-volatile: builds up
What are 3 ways to control pH plasma?
buffering system (CO2/HCO3, phosphate, ammonia)
lung system (CO2 levels)
kidney system (HCO3- levels, and execrating non-volatile acids)
What are the 3 buffering system examples?
CO2/HCO3
phosphate
ammonia
What is the job of a proton buffer?
minimize changes in pH
The HCO3-/CO2 buffering system has a poor pK. Why is this ok?
CO2 can be blown off and HCO3 levels can be very high
What are 2 reasons kidneys excrete H+ into the lumen of tubules?
- reabsorb filtered HCO3- (protons not excreted)
- excrete non-volatile acids (protons excreted)
What’s the net uptake of acid in one day?
30
What is the net amount of metabolic acid produced in one day?
55
(15 CO2; 40 non-volatile acid)
How much H+ is excreted in one day?
70
How much HCO3- is reabsorbed in one day?
4320
What are 3 steps the body takes when a load of acid is introduced?
- plasma HCO3- immediately buffers H+
- CO2 generated from 1. is blown off
- new HCO3 forms in kidneys and replaces HCO3 used in 1.
Draw the steps of HCO3 reabsorption?
slide 11
Draw the steps of H+ excretion?
slide 11
What are the 2 titratable acids?
H2PO4-
NH4
What are the 2 fates of H+ secreted in the lumen?
- combined to make water to generate new HCO3
- excreted as titratable acids
Is the HCO3 made in H+ excreted considered new or old?
new
Is HCO3 made in HCO3 reabsorption considered new or old?
old
Where is most of the HCO3 reabsorbed in the nephron?
proximal tubule
Where is the other two 10% of HCO3 reabsorbed?
thick ascending limb
distal tubule
The majority of new HCO3- is generated from H2PO4 or NH4?
NH4
What 3 segments of the nephron participate in acid secretion?
proximal tubule
thick ascending limb
cortical collecting duct
How does the proximal tubule play a role in acid secretion?
Cl/HCO3- exchanger (bicarbonate reabsorption)
How does the thick ascending limb play a role in acid secretion?
Cl-/HCO3- exchanger (bicarbonate reabsorption)
How does the cortical collecting duct play a role in acid secretion?
alpha and beta intercalated cells (bicarbonate reabsorption)
What is the importance of glutamine breakdown and urea formation?
important for excretion amine groups
What’s the difference between glutamine breakdown and urea formation?
glutamine breakdown: generates new HCO3
urea formation: looses HCO3
Is urea formation or glutamine breakdown stimulated by acidosis?
glutamine breakdown
- forms new HCO3-
Kidneys regulate plasma osmolality by regulating ______ osmolality
urine (creating a concentrated or dilute urine)
Dilute urine is a result of reabsorption of _____
NaCl
Concentrated urine is a result of reabsorption of _____
H2O
To make a concentrated urine, what 2 things are needed?
- H2O permeable nephron segments
- hyper-osmotic medullary intersistum
What is the role of ADH?
increases water reabsorption (more concentrated urine)
How does ADH work?
binds to receptors on principle cells which causes more aquaporins to be inserted on apical side = more water reabsorption
What are 2 stimulators of ADH?
- increased plasma osmolality
- decreased ECF
What is the main stimulator of ADH?
increased plasma osmolality
What are the 2 feedback loops used to return elevated plasma osmolality back to normal?
- increase thirst = increase water intake
- release ADH = increased water reabsorption
What 2 segments of the nephron are the most water permiable?
proximal tubule
thin descending limb
Where is ADH most active in the nephron?
inner medulla collecting duct
Where in the nephron does ADH first appear?
distal tubule
What are the 2 steps to generating a hypersmotic medullary interstitum?
- reabsorb H2O in thin descending loop
- reabsorb NaCl in tALH anf TAL
Is the medullary intersistum hyperosmotic or hyposmotic at the end of the thin descending limb?
hypososmotic
Is the medullary intersistum hyperosmotic or hyposmotic at the end of the thick ascending limb?
hyperosmotic
Does tALH and TAL have water permiability?
no
NaCl is actively or passively reabsorbed out of thin ascending limb?
passively
NaCl is actively or passively reabsorbed out of thick ascending limb?
actively
Reabsorption of NaCl by the ascending limb creates a gradient between the interstitum and the tubule lumen and is amplified by …
counter current loop
The countercurrent multiplier loop causes a gradient that drives NaCl to the _______ of the nephron in the medulla
tip
What is the single effect in the countercurrent multiplier loop?
movement of NaCl out of ascending limb which increases the osmolarity of interstitium
What is the osmotic equillibrium in the countercurrent multiplier loop?
entering isosmotic fluid (from PT) is turned hyperosmotic b/c water is leaving lumen
What is tubule flow countercurrent multiplier loop?
concentrated fluid moves to the tip of loop which drives more NaCl into intersistium (hyperosmotic interstitum)
What are the 3 steps of the countercurrent multiplier loop?
- single effect
- osmotic equillibrium
- tubule flow
What are 2 methods to prevent blood from picking up NaCl and washing it out of interstitum?
- vasta recta
- decrease blood flow
What does the vasta recta do?
capillaries running parallel to LH that pick up salt but then deliver it back to intersistum
Where are vasta recta capillaries located?
parallel to LH
Urea concentration _________ as you get deeper in the medulla?
increases
What secretes 50% of urea?
tip of loop of Henle
Concentrated urea in the collecting duct is reabsorbed in the presence of _______
ADH
decreased H2O intake = ________ ADH = ________ urea recycling = _______ urea build up in intersisitum = ________ interstitium osmolarity = ________ water reabsorption = __________ H2O excretion
increase ADH
increase urea recycling
increase build up
increase osm
increase reabsorption
decreased excretion
If water intake decreases what happen to ADH levels?
increases
If ADH increases urea will build up in interstitum, why?
driving force for water reabsorption to hydrate body
Respiratory acidosis…
pH:
[HCO3-]:
PCO2:
equation:
pH: decrease
[HCO3-]: increase
PCO2: increase
equation: right
Respiratory alkalosis…
pH:
[HCO3-]:
PCO2:
equation:
pH: increase
[HCO3-]: decrease
PCO2: decrease
equation: left
Metabolic acidosis…
pH:
[HCO3-]:
PCO2:
equation:
pH: decrease
[HCO3-]: decrease
PCO2: NA
equation: left
Metabolic alkalosis…
pH:
[HCO3-]:
PCO2:
equation:
pH: increase
[HCO3-]: increase
PCO2: NA
equation: right
In metabolic acidosis compensation, which is larger…[HCO3]/[CO2]?
small/large
* needs to decrease CO2
In metabolic alkalosis compensation, which is larger…[HCO3]/[CO2]?
large/small
* needs to increase CO2
In respiratory acidosis compensation, which is larger…[HCO3]/[CO2]?
large/small
* needs to increase CO2
In respiratory alkalosis compensation, which is larger…[HCO3]/[CO2]?
small/large
* needs to decrease CO2
