PPQs 5-8

Question 1

Describe how ultrafiltration produces glomerular filtrate

Answer 1

hydrostatic pressure
small molecules
pass through basement membrane
proteins too large
presence of podocytes

Question 2

Explain how lack of insulin affects reabsorption of glucose

Answer 2

high conc. glucose in blood
high conc. in filtrate
reabsorbed by facilitated diffusion/active transport
requires proteins/carriers
these are working max. rate
not all glucose reabsorbed

Question 3

Explain the role of the loop of Henle in the absorption of water from the filtrate

Answer 3

Na+ actively removed in ascending limb (against conc. gradient)
ascending limb impermeable to water
Na+ diffuse in descending limb
(maintains water potential gradient for water reabsorption)
water moves out of descending limb
low water potential in medulla/tissue fluid
water leaves collecting duct
by osmosis

Question 4

Explain the role of ADH in the production of concentrated urine

Answer 4

when water potential blood too low
detected by receptors in hypothalamus
pituitary secretes ADH
ADH increases permeability of collecting duct
more water reabsorbed
by osmosis down water potential gradient