Physiology 4 + 5 Flashcards
what is the normal GFR in litres per day?
180
kidneys reabsorb creatinine T or F
F
of reabsorption and filtration, which is specific?
reabsorption
where is most filtered fluid reabsorbed in the nephron?
proximal tubule (about 80ml/min)
give examples of substances secreted from the proximal tubule
Ach adrenaline noradrenaline drugs H+
what substanes are reabsorbed by the proximal tubule?
sugars amino acids phosphate sulfate lactate
epithelial cells are polarised T or F
T
what membrane does a substance have to cross to get from the tubular lumen to the tubular epithelial cells?
apical membrane
what does paracellular reabsorption mean?
substance is reabsorbed through tight junctions between epithelial cells
what does transcellular reabsorption mean?
substance is reabsorbed through the epithelial cell itself
how does secondary active transport differ from primary?
carrier molecule is transported coupled to the concentration of an ion eg Na (rather than just moving against its own conc gradient)
how much filtered salt is reabsorbed within the proximal tubule?
about 2/3
which ion leaves the cell in the Na/K pump?
Na
how is sodium conc in the ECF kept higher than the ICF?
any Na that makes it into the cell is forced to leave by the Na/K pump
Na leaves the epithelial cells by what route?
transcellular
Cl and H20 leave the epithelial cells by what route? why are they reabsorbed?
paracellular; an osmotic and electrochemical gradient are created by the movement of Na into the blood
plasma proteins are more concentrated in the proximal tubule than in the afferent arteriole: T or F
T (glomerular filtration decreased volume of fluid so more proteins in a smaller vol)
how is the osmolarity of the tubular fluid kept unchanged?
reabsorbing water and salt in equal proportions
reabsorption of glucose happens where?
proximal tubule
Na/K pump is located in what membrane?
basolateral membrane
Na/glucose transporter is located in what membrane?
apical membrane
rate of filtration is equal to…
plasma conc x GFR
kidneys filter most glucose at low glucose concentrations T or F
F, filter at high glucose concs
if kidneys still filter a substance when reabsorption stops, what happens?
it is excreted as urine
does reabsorption have a limit?
yes, when the transport mechanisms become saturated
what kidney functions will appear as an exponential line that plateaus?
reabsorption mainly
secretion
the tubular fluid is ___ when it leaves the proximal tubule
iso-osmotic
what does iso-osmotic mean in terms of the proximal tubule
it has the same osmolarity as the plasma (300mosmol/l)
main function of the loop of henle?
generate a cortico-medullary solute concentration gradient
the cortico-medullary solute conc gradient will form what tonicity of urine?
hypertonic urine
the tubular fluid in the medulla has a higher osmolarity than in the cortex T or F?
T
what is countercurrent flow?
fluid moving down the descending limb as well as fluid moving up the ascending limb
what type of nephron has longer loops of henle?
juxtamedullary nephrons
cells of the ___ limb are very permeable to water but do not reabsorb salt
descending
cells of the ___ limb are very permeable to salt but impermeable to water
ascending
at what parts of the ascending limb is reabsorption carried out via active transport/diffusion
diffusion at the thin lower end of the limb
active transport at the thick, upper part of limb
what kind of fluid bathes the wall of the tubule?
interstitial fluid
TALH triple cotransporter pumps ions ___ ___ the lumen
out of
where are Na and Cl reabsorbed in the loop of henle?
its thick upper part of the ascending limb
what group of drugs can block the triple co-transporter?
loop diuretics
the triple co-transporter is located in what membrane?
apical membrane
how does chloride get into and out of the epithelial cells of the loop of henle?
in via triple co-transporter
out via potassium/cl transporter
what type of ion undergoes “recycling” to get in and out of the loop of henle?
K+
taking salt away from the tubular fluid will have what effect on its osmolarity?
will decrease it to 200 (was 300mosmol/l)
when salt is reabsorbed in the ascending loop of henle, where does it go? what effect will it have on this substance’s osmolarity?
into the intersitial fluid (will increase its osmolarity to 400mosmol/l)
why does the descending limb’s osmolarity increase during reabsorption of salt?
water leaves this area by osmosis to dilute the now concentrated interstitial fluid (desc limb’s tubular fluid now becomes concentrated)
when is steady state said to have been reached
when tubular fluid of the ascending limb is 100mosmol/l
what tonicity of fluid is in the proximal tubule?
iso-osmotic
what tonicity of fluid is in the ascending limb?
hypotonic aka hypoosmotic
how much urea is reabsorbed back into the blood?
50%
what 2 substances set up the corticomedullary conc gradient?
salt
urea
what does countercurrent multiplication do?
concentrate the medullary intersitial fluid
why do we need the corticomedullary conc gradient?
allows you to produce urine of different volumes and concentrations
if you have a high content of vasopressin/ADH in the blood, are you hydrated or dehydrated?
dehydrated
blood osmolarity ___ as it dips down into the medulla
rises (more salt gained)
blood osmolarity ___ as it rises into the cortex
falls (more water gained)
osmolarity increases as the level of ___ increases
salt
there is no net change of osmolarity in the blood coming into and leaving the vasa recta: T or F
T
vasa recta capillaries are impermeable to NaCl and water T or F
F, are considered “leaky” so are permeable
main job of the vasa recta?
keeps the corticomedullary conc gradient in place
