Adult knees

Question 1

function of kidneys

Answer 1

excretion
homeostasis (bp, ECF volume, osmolarity, ions, pH)
hormone production (renin)

Question 2

two types of nephrons

Answer 2

cortical nephrons (short loop of henle)
juxtaglomedullary nephrons (long loop of henle in renal medulla surrounded by vasa recta)

Question 3

if bowman’s capsule is damaged

Answer 3

proteinuria (protein in filtrate)

haematuria (RBC in filtrate)

Question 4

three layers of bowman’s capsule

Answer 4

fenestrated endothelium
collagen basement membrane
podocyte filtration slits (epithelium of bowman’s capsul)

Question 5

autoregulation of glomerular filtration rate (GFR) by two mechanisms:

Answer 5

myogenic (stretch) response

• controls resistance renal arterioles
• ↑ arterial pressure -> stretch renal afferent arteriole -> ↑ flow -> vascular smooth muscle contracts -> ↑ resistance -> flow back to normal

tubuloglomerular feedback
- ⬆ GFR -> ⬆ flow through tubule and past macula densa -> afferent arteriole constricts -> ⬆ resistance -> ⬇ hydrostatic pressure in glomerulus -> ⬇ GFR

Question 6

how to measure glomerular filtration rate (GFR)

Answer 6

inulin
(can be filtered, not reabsorbed or secreted, not metabolised or produced, not alter GFR)

GFR = ([inulin] in urine x volume filtrate per min)/ [inulin] in blood plasma

Question 7

proximal convoluted tubule

Answer 7

everything is reabsorbed

e.g. Na+, K+, Ca2+, Mg2+, Cl-, HCO3-, water, glucose, amino acids, protein, vitamins, lactate, urea, uric acid

Question 8

ADH 
produced
released
stimulated by 
affects

Answer 8

supraoptc and paraventricular nuclei of hypothalamus

posterior pituitary gland

increase plasma osmolarity
- ⬆ plasma osmolarity -> osmoreceptor -> posterior pituitary -> ⬆ ADH
decrease blood pressure
low blood volume

increases water reabsorption

• increases water permeability of collecting duct
• increases urea permeability in inner medullary region of collecting duct
• increases NaCl reabsorption in thick ascending limb

Question 9

ADH at site of action

Answer 9

ADH binds to receptor on basolateral surface
stimualtes adenylyl cylase to generate cAMP and activate protein kinase
increase insertion of AQP2 water channels into apical surface
increase water reabsorbed into blood

Question 10

increase in blood osmolarity from water deprivation response

Answer 10

increase ECF osmolarity
supraoptic and paraventricular nuclei in hypothalamus
- ADH release -> collecting duct more water permeable -> water retention in kidney
lateral preoptic area
- thirst -> drink water
blood osmolarity back to normal

Question 11

decrease in blood osmolarity from excessive fludi ingestion response

Answer 11

decrease ECF osmolarity
supraoptic and paraventricular nuclei in hypothalamus
- ADH release suppressed -> collecting duct less water permeable -> water excretion in kidney
lateral preoptic area
- thirst suppressed
blood osmolarity back to normal

Question 12

ADH controlled by

Answer 12

osmoregulators
atrial natriuretric peptide (ANP) inhibits (triggered by atrial stretch)
alcohol inhibits
nicotine stimulates

Question 13

aldosterone 
produced
released
stimulated by 
affects

Answer 13

produced and released by zona glomerulosa of adrenal cortex

increased K+
decreased blood pressure (via RAAS)

regulates Na+ balance
- increase bp and bv -> increase Na+ reabsorption and K+ secretion in distal tubule and collecting duct

Question 14

aldosterone site of action

Answer 14

DCT and collecting duct
aldosterone binds to receptor in cytoplasm
initiates transcription
increase epithelial Na channels ENaC in apical surface
increase Na+/K+ pumps in basolateral surface
increase Na+ uptake and Cl- follows

Question 15

renin affects

Answer 15

decrease blood pressure

decrease Na+ delivery to macula densa

Question 16

ANP
produced and stimulated by
affects

Answer 16

increase volume -> increase atrial stretch -> atria produce and release ANP

generally increases renal Na+ and water excretion

in hypothalamus decrease ADH
in kidney decrease NaCl and H2O reabsorption, decrease renin
in adrenal cortex decrease aldosterone

Question 17

loop of henle countercurrent multiplier

Answer 17

descending limb

• permeable to water, impermeable to solute
• tubular fluid out into higher osmolarity interstitium

thick ascending limb

• impermeable to water, permeable to solute
• creates high osmolarity in interstium

Question 18

distal convoluted tubule

Answer 18

NaCl moves out (Na/Cl cotransporter blocked by diuretics)

H2O stays in

Question 19

collecting duct principal cells

Answer 19

balance Na+ and K+ via ion channels
aldosterone increase Na+ channels and Na+/K+ ATPases
ADH increase AQP2

Question 20

collecting duct intercalated cells

Answer 20

acid-base homeostasis of blood plasma
α-cells respond to acidosis
- H+ to collecting duct to be excreted out
- HCO3- reabsorbed to interstitial space
β-cells respond to alkalosis
- HCO3- to collecting duct to be excreted out
- H+ reabsorbed to interstitial space

Question 21

macula densa responds to changes in NaCl delivery

Answer 21

⬆ glomerular pressure and plasma flow
⬆ GFR
⬆ NaCl to DCT
⬆ flow rate sensed by macula densa
⬆ paracrine signals e.g. ATP, aldosterone
paracrine signalling ⬆ afferent resistance