tubular function

Question 1

how much is reabsorbed in the renal corpuscle?

Answer 1

99%

Question 2

describe sodium handling

Answer 2

na transport facilitates reabsorption of nutrients, water and ions
65% reabsorbed in PCT
25% reabsorbed in ascending loop of henle
8% in DCT- depending on rn
98% reabsorbed

Question 3

what is passive diffusion?

Answer 3

movement of molecules from high to low concentration until equilibrium is reached

Question 4

in what direction is the concentration gradient between the PCT and peritubular capillaries

Answer 4

high -> low

tubules lumen -> tubule wall -> interstitial space -> peritubular capillary

Question 5

how does water move?

Answer 5

aquaporins

Question 6

how do glucose and aa move across the apical surface?

Answer 6

sodium co-transporters

Question 7

describe how the proximal tubule reabsorbs 2/3 of filtrate

Answer 7

Na+K+ pump on basolateral membrane facilitates 65% reabsorption, everything else follows Na+ eg. water follows by osmosis, chroride follows electrical gradient

Question 8

what does Na+ active transport facilitate?

Answer 8

100% nutrient reabsorption
65% water reabsorption
65% neg ions follow electrical gradient
no effect on waste removal
remaining filtrate continues through loop of henle

Question 9

what are the 3 parts of the loop of henle?

Answer 9

thin descending limb
thin ascending limb
thick ascending limb

Question 10

what are the loop rules?

Answer 10

thin descending contains aquaporins-freely permeable to water
both ascending do not contain aquaporins-impermeable to water
thick ascending - site of active sodium reabsorption

Question 11

how does sodium reabsorption occur?

Answer 11

via NKCC2 on apical membrane

Question 12

what is countercurrent multiplication?

Answer 12

mechanism for reabsorbing water from tubular fluid

energy used to create osmotic gradient-produce concentrated urine

Question 13

why does the vasa recta employ counter current exchange?

Answer 13

to maintain concentration gradient of the medulla

Question 14

what is the function of the distal convoluted tubule?

Answer 14

fine-tuning - site of fluid volume and electrolyte regulation
Na & water reabsorption hormonally reg.
ADH- increases reabsorption
aldosterone- increases Na+ reabsorption
AND- promotes Na+ secretion

Question 15

how does ADH affect urine production?

Answer 15

acts on distal and collecting tubules
insertion of aquaporins allows water to be reabsorbed from the filtrate
small vol. cons. urine prod.

Question 16

how does aldosterone affect urine production?

Answer 16

acts on distal and collecting tubules
upregulates activity and insertion of Na+K+ pumps and channels
small vol. conc. unrine prod.

Question 17

how does ANH affect urine production?

Answer 17

acts on distal and collecting tubules
inhibits action of ADH and aldosterone
large vol. dilute urine prod.