Renal Review Flashcards
Differentiate superficial cortical nephrons and juxtamedullary nephrons
Superficial cortical: glomeruli in outer cortex; relatively short Loops of Henle descending into only the outer medulla
Juxtamedullary: glomeruli larger, which + higher glomerular filtration rates; long loops of henle
The glomerulus is a glomerular capillary network emerging from an _______ and exiting via a _______
afferent arteriole
efferent arteriole
Long loops of henle in juxtamedullary nephrons are essential in _________
concentrating urine
________ branch from efferent arterioles
Peritubular capillaries
Peritubular capillaries, in juxtamedullary nephrons, also have ______, which are long, hairpin-shaped blood vessels surrounding the loop of Henle. They help participate in ______
vasa recta
osmotic exchange, concentrating urine
Water accounts for ______ of BW
60% (50-70%)
The major cations of the ICF are ______. Anions?
K+
Mg+
organic phosphates, proteins
What is an ultrafilatrate of plasma?
interstitial fluid
What is the average osmolarity?
290-300 mOsm/L
In a ____ state, intracellular osmolarity + extracellular osmolarity and water shifts freely across membranes
steady
Volume contraction is a(n) [increase/decrease] in [ECF/ICF] volume, and volume expansion is a(n) [increase/decrease] in [ECF/ICF] volume
decrease, ECF
increase, ECF
Give examples of volume contraction
diarrhea
water deprivation
adrenal insufficiency
Give examples of volume expansion
infusion of isotonic NaCl
high NaCl intake
syndrome of inappropriate ADH
What does a low renal clearance mean?
very little or none of the substance is removed
Why is renal clearance important?
uses the rate at which a compound is “cleared” from the body (expected in urine) to determine aspects of renal function
What is the equation for renal clearance?
_____ is used to estimate renal plasma flow
PAH (volume of blood delivered to kidneys per unit time)
______ is used to estimate GFR
insulin or creatinine
________ should have zero filtration
Albumin
A CR < 1.0 means what
either substance is not filtered or it is filtered and reabsorbed
The major mechanism for changing renal blood flow is by changing __________
arteriolar resistance
T/F: Renal blood flow (RBF) is inversely proportional to resistance of renal vasculature (mainly by arterioles)
TRUE
There are more alpha-1 receptors on [afferent/efferent] arterioles. This [increases/decreases] GFR & RBF
afferent
decreases
What affects efferent arterioles more because they are more sensitive to low levels of this? Does this increase or decrease GFR?
angiotensin II
increase
If there is high angiotensin II, what happens to GFR?
decreases
because high levels of angiotensin II has a greater effect on AFferent arterioles (low levels affect efferent)
ANP causes [constriction/dilation] on [afferent/efferent] arterioles. What happens to renal vascular resistance, RBF, and GFR?
dilation
efferent
decrease
increase
increase
What effect do prostaglandins have on afferent and efferent arterioles?
vasodilation on both to protect renal blood flow
- responding to SNS activity
What modulates vasoconstriction of SNS?
prostaglandins and dopamine
How does dopamine affect afferent and efferent arterioles?
dilates renal arterioles - particularly useful in hemorrhage
In the myogenic hypothesis, [increased/decreased] arterial pressure stretches blood vessels and ultimately [increases/decreases] resistance to blood flow
increased
increases
What does tubuloglomerular feedback hypothesis ultimately do?
constrict afferent arteriole
(macula densa in early distal tubule senses increased load)
How do you calculate renal blood flow?
RBF = RPF/(1 - Hct)
The amount of substance entering an organ equals the amount of substance leaving the organ is the _____ principle
Fick
Is true RPF or effective RPF more feasible?
effective
effective RPF = clearance of PAH
What is the first step in forming urine?
glomerular filtration
T/F: Ultrafiltrate in glomerulus contains water, small solutes, proteins, and blood cells
FALSE
NO proteins or blood cells
The renal corpuscle is responsible for ________
filtering blood
What are the 2 cell types in the glomerulus?
endothelial (large pores)
mesangial cells (modified smooth muscle cells located between capillaries; extraglomerular & intraglomerular)
What are the layers of the glomerular capillary?
endothelium - no filtering of blood cells
basement membrane - no filtration of plasma proteins
epithelium: podocytes; no proteins here
There is a [positive/negative] charge on the glomerular capillary barrier which helps large solutes be repelled
negative
What is the dominant pressure across glomerular capillaries?
hydrostatic forces in capillary blood
Which oncotic pressure should be 0?
one in Bowman’s space; no protein should be here
What is Kf in the Starling equation?
water permeability of glomerular capillary wall
Net ultrafiltration pressure always favors filtration [in/out] of capillaries
OUT
T/F: The change in GFR depends on which arteriole is affected
TRUE
The clearance of inulin is = to
GFR
What is filtration fraction
expresses relationship between GFR and RPF
FF = GFR / RPF
What are some issues with using creatinine as a GFR marker?
only when 75% nonfuncitonal
patients with low muscle mass
Can you look at BUN to alone evaluate renal function?
NO - look at creatinine:BUN ratio
What are some issues with using BUN as a GFR marker?
not produced at a constant rate
depends on dietary protein intake
measuring during fasting or post-prandial
An increased BUN:creatinine ratio means ______ has increased
BUN
No change in ratio means that BUN:creatinine ratio ______
both increased/decreased
What is good about SDMA?
increases earlier than creatinine as kidney function decreases
not affected by muscle mass
What portion of kidney action requires energy?
reabsorption
secretion
If filtered load is less than excretion rate, net ______ of a substance occurs
secretion
Where does glucose reabsorption occur?
proximal convoluted tubule
What is the type of transport used in glucose transport to the proximal convoluted tubule?
2Na+/glucose co-transport
Most Na+ reabsorption occurs where?
proximal convoluted tubule
What part of the nephron is impermeable to water?
thick ascending limb
What fine-tunes Na+ reabsorption? Where?
aldosterone
late distal tubule
collecting ducts
T/F: 85% of HCO3- by the mid-PCT is reabsorbed
TRUE
What is Fanconi Syndrome?
failure to reabsorb glucose, bicarbonate, phosphates, certain aa
What is absorbed in the late PCT?
NaCl - paracellular and cellular routes
What are the cellular and paracellular routes of NaCl in the late proximal tubule?
cellular: Na+/H+ exchanger; Cl-/formate exchanger
paracellular: tight junctions loose and permeable to small solutes; Cl- diffuses, followed by Na+
In the PCT, [water/Na+] follows passively
water
Na+ is reabsorbed first and water follows
If filtration fraction increases, then oncotic pressure in peritubular capillaries [increases/decreases] & reabsorption [increases/decreases]
increases
increases
Principal cells are for [Na+/K+/H+] [reabsorption/secretion/excretion], and alpha-intercalated cells are for [Na+/K+/H+] [reabsorption/secretion/excretion]. Where?
principal: Na+ reabsorption, K+ secretion
alpha-intercalated: K+ reabsorption, H+ secretion
Late DT & CD
Hyperkalemia is concerned with high [ECF/ICF] concentration. It leads to [depolarization/hyperpolarization].
ECF
depolarization (hyperexcitable cells)
Hypokalemia is concerned with high [ECF/ICF] concentration. It leads to [depolarization/hyperpolarization].
ICF (decrease in ECF conc.)
hyperpolarization
______ increases Na+/k+ ATPase activity
insulin
[Acidemia/alkalemia] is associated with hyperkalemia.
acidemia
[Acidemia/alkalemia] is associated with hypokalemia.
alkalemia
Which ion’s concentration varies by diet that determines urinary excretion?
K+
The magnitude of _____ secretion is determined by the size of the electrochemical gradient for ____ across the liminal membrane
K+
K+
About ______ of plasma phosphate filtered
90%
What transporter in the proximal tubule is for phosphate?
Na+/phosphate co-transporter
Which hormone stimulates Ca2+ reabsorption in the DCT of kidneys?
PTH
What is the only nephron segment where Ca2+ reabsorption NOT coupled to Na+ reabsorption?
early DT
Where is there countercurrent multiplication in the kidney?
loop of henle
When water reabsorption increases, what happens to urine osmolarity and urine volume?
osmolarity increases
volume decreases
What is the goal of countercurrent multiplication?
concentrate urine
The descending limb is [permeable/impermeable] to water
permeable
The tubular fluid concentration at which part of the loop determines maximal urine concentration?
base of the loop
What are the 3 actions of ADH?
act on mTAL to increase activity of Na/K/2Cl cotransporter
act on principal cells in late distal tubule and collecting tubule to increase water reabsorption in principal cells
acts on inner medullary collecting ducts to increase urea transporter-1
What does angiotensin 2 stimulate in the PT?
Na+/H+ exchange
HCO3- reabsorption
An increase CO2, it will [increase/decrease] reabsorption of HCO3-
increase
H+ is primarily excreted by _____
alpha-intercalated cells
Which enzyme in the proximal tubule metabolizes glutamine to glutamate + NH4+?
glutaminase
