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68 Cards in this Set

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What are the two portions of the collecting duct?
a cortical portion
medullary portion
The changes in osmolality and volume in the collecting ducts depend on the amount of vasopressin acting on the ducts. TRUE/FALSE
TRUE
Vasopressin(ADH) increases the permeability of the collecting ducts to water. TRUE/FALSE
TRUE.
The key to the action of vasopressin on the collecting ducts is due to what substance?
Aquaporin-2. This aquaporin is stored in vesicles in the cytoplasm of principle cells. vasopressin causes rapid insertion of these vesicles into the apical membrane of cells.
The function and physiology of these vesicles is due to what?
The effect is mediated via the vasopressin V2 receptor, cyclic AMP, protein kinase A and a molecular motor, one of the dyneins.
What are dyneins?
Molecular motor proteins?
They have 2 heads, with their neck pieces embedded in a complex of proteins. Cytoplasmic dynein has a function like that of conventional kinesin, except that it moves particles and membranes to the end of the microtubules. The heads of these molecules hydrolyze ATP and use energy to produce motion.
maximum urine osmolality is about 2500mosm/kg in dogs, about 3200 in lab rats, and as high as 5,000mosm/kg in certain desert rodents. TRUE/FALSE
TRUE.
What is nephrogenic diabetes insipidus?
The collecting ducts fail to respond to vasopressin. two forms are recognized. The gene for the V2 receptor is mutated, making the receptor unresponsive. In the other form, the autosomal gene for aquaporin-2 is mutated.
What is a counter-current system?
It is a system in which the inflow runs parallel to, counter to and in close proximity to the outflow for some distance.
The ECF is app. 4X as salty deep in the medulla as it is in the cortex. TRUE/FALSE
TRUE. The nephron loop acts as a countercurrent multiplier, which continually recaptures salt and returns it to the deep medullary tissue.
Why is it called a multiplier system?
It multiplies the salinity deep in the medulla, and a countercurrent mechanism because it is based on fluid flowing in opposite directions in two adjacent tubules.
Give a general synapse of the C/M system.
1. More salt is continually added by the PCT.
2. The higher the osmlarity of the ECF, the more water leaves the descending limb by osmosis.
3. The more water that leaves the descending limb, the saltier the fluid is that remains in the tubule.
4. The saltier the fluid in the ascending limb, the more salt the tubule pumps into the ECF.
5. The more salt that is pumped out of the ascending limb, the saltier the ECF is in the renal medulla.
Most or all of the ascending limb(thick segment) by contrast is impermeable to water. TRUE/FALSE
TRUE. It has however, active transport pumps that cotransport Na+, K+ and Cl- into the ECF. This keeps the osmolarity of the renal medulla high.
What happens to the fluid as it approaches the cortex?
The tubular fluid becomes more dilute as it approaches the cortex, and is only about 100mOsm/L at the top of the loop.
What is the fate of urea in the collecting duct?
Ther C/D helps to maintain the osmotic gradient. Its lower end is somewhat permeable to urea, which diffuses down its concentration gradient out of the duct and into the ECF.
What happens to the urea once in the tubule?
Some of this urea enters the descending thin segment of the nephron loop and travels to the DCT.
neither the thick segment of the loop nor the DCT is permeable to urea, so urea remains in the tubules and returns to the collecting duct. TRUE/FALSE
TRUE. There is a continual recycling of urea from the collecting duct to the medulla and back. Urea accounts for about 40% of the high osmolarity deep in the medulla.
What is the countercurrent exchange system?
The capillaries of the medulla could carry away the urea and salt that produce the high osmolarity. The vasa recta that supply the medulla, form a countercurrent system of their own that prevents this from happening. Blood flows in opposite directions in adjacent parallel capillaries. These capillaries form a CCES.
What exactly do the vasa recta exchange?
Blood in the vasa recta exchanges water for salt as it flows downward into the deep medulla- water diffuses out of the capillaries and salt diffuses in. As the blood flows back toward the cortex, the opposite occurs, it exchanges salt for water.
Urea contributes to the establishment of the osmotic gradient in the medullary pyramids and to the ability to form a concentrated urine in the collecting ducts. TRUE/FALSE
TRUE.
Urea transport is mediated by urea transporters, by facilitated diffusion. TRUE/FALSE
TRUE. There are atleast 4 isoforms of the transport protein, UT-A in the kidneys(UT-A1- UT-A4. UT-B is found in erythrocytes. A high protein diet increases the ability of the kidneys to concentrate the urine.
During excretion of an average osmotic load, the maximum urine flow that can bbe produced during a water diuresis is about...
16mL/min
What happens if water is ingested at a higher rate than 16mL/min?
Swelling of the cells because of the uptake of water from the hypotonic ECF becomes severe and rarely, the symptoms of water intoxication may develop. Swelling of brain cells may result in seizures, coma and death.
Incautamente
incautiously, imprudently
Essere incensurato
to have a clean record
Incespicare
incespicare nel parlare
to stumble
to stumble on ones words
inclito
illustrious
Mal gliene incolse
No good came of it
Incolume
unhurt
attentare all' incolumita di qualcuno
to make attempt on somebody's life
Incompiutezza
incompleteness
inconciliabile
irreconciliable
inconfutato
indisputable
inconsueto
unusual
incordare
to string, to rope
Essere incurante della propria salute
to neglect ones health
indicibile
indescribable
Indefesso
tireless
Indispettito
angry, cross
Sii indulgenet
Dont be too severe
Corrispondenza inevasa
unanswered mail
prognosi infausta
fatal prognosis
Infido
unreliable
Mi dispiace infinitamente
Im awfully sorry
Infruttuosamente
unsuccessfully
Inganno ottico
optical illusion
dar prova d' ingegno
to show ingenuity
Ingegnosamente
cleverly
Ingraticciata
trellis
Inimicarsi
to become somebody's enemy
Inintelligibile
beyond human understanding
Inoltrato
a maggio inoltrato
very late
well into May
Inopinabile
unimaginable
Inquisitivo
enquiring
Inscusabile
inexcusable
T'insegno io a rigare diritto
Ill teach you not to misbehave
Intarsiare
to inlay(mobili)
Integerrimo
very honest
Intervallare
to space out(scrivere)
Intimorire
to frighten
Intirizzito
numb
Invalicabile
impassable
Inviperito
furious
Invizzire
to wrinkle, to shrivel
Non mi importa uno iota
I couldnt care less
Irrepribile
untraceable
Irreprensibile
faultless
irrilevante
insignificant