Lecture 5 - Nephron Function II

Question 1

Short loop nephrons?

Answer 1

have water-tight tight junctions, meaning Na+ can travel through NXCC2 without water movement causing hypertonic ECF

Question 2

Where does water go from higher medulla?

Answer 2

vasa recta - counter direction to nephron flow, water exits and solute enters as descends, and vice versa as ascends

Question 3

Early distal convoluted tubule?

Answer 3

removal of NaCl without water for further dilution - blocked by thiazide diuretics, for hypertension and heart failure

Question 4

Late distal convoluted tubule - Principle cells?

Answer 4

reabsorb Na+ through ENaC, lumen is negative, K+ secreted

Question 5

Thiazide diuretic adverse effect?

Answer 5

hypokalaemia, due to increaed Na+ in late convoluted tubule - can cause ventricular arrhythmias

Question 6

Aldosterone and principle cells?

Answer 6

up-regulates activators of ENaC, and induces more ENaC and ATPase

Question 7

Diffusion trapping?

Answer 7

NH3 passively diffuses, but binding to H+ makes NH4+ which is trapped in urine - H+ is loitered to allow more H+ to be added

Question 8

Intercalated cells?

Answer 8

secrete H+ via H+ ATPase for HCO3- reabsorption and production

Question 9

Water movement @ collecting duct?

Answer 9

anti-diuretic hormone (ADH) forms aquaporin channels on the apical membrane

Question 10

Passive hypothesis?

Answer 10

urea bcomes high in cortical collecting duct due to ADH induced water reabsorption, ADH increases urea and H20 permeability in medulla collecting duct, urea deposited into interstitum, H2O causes NaCl to drop and move into interstitum from loop of Henle