Nephron physiology Flashcards
Early proximal tubule
all glucose and aa reabsorbed
2/3 fluid - isotonic, H2O follows
2/3 electrolytes
Na+ absorption with HCO3-
Cl- diffuses through following Na+
Review diagram page 599
Draw relative concentrations along the proximal tubule
page 600
above the TF/P line: reabsorbed slower than H2O
“Plasma Concentrations Increase Unless Cleared by Kidneys”
PAH Creatinin inulin urea Cl- K+ and Na+ (isotonic)
Below TF/P line - reabsorbed faster than water:
HCO3-, aa, glucose
Late Proximal tubule
Na+ absorption with Cl-
Anion reabsorption w/ H+ coupling
Page 600
Proximal tubule (anions and cations)
Organic anions and cations into lumen
alpha-ketoglutarate counter transport for anion from interstitial to tubular cell
Organic cation uses H+ counter exchanger to get to lumen
page 600
Thin descending limb
water reabsorption
impermeable to Na+
H2O follows osmotic gradient into hypertonic medulla
luminal fluid concentrated
Thick ascending limb
active reabsorption of Na/K/2Cl to create hypertonic interstitium
impermeable to H2O - filtrate less concentrated (more dilute)
Drugs inhibiting Na/K/2Cl symporter
loop diuretics -> isotonic water excretion
Early distal tubule
active reabsorption of Na+, Cl-
generally impermeable to H2O
PTH acts on Na+/Ca2+ counter transporter to increase resorption of Ca2+
Na/Cl- cotransporter follows gradient established by Na/K ATPase
Ca2+ channel
page 601
Principal cells
reabsorb H2O and Na+
Secrete K+
Intercalated cells
secrete H+ or HCO3-
reabsorb K+
Types of intercalated cells
Alpha cells: H+ secretion (1st letter of alphabet, 1st element)
Beta cells - Bicarb secretion (Bs)
Collecting tubule intercalated cell
H/K ATPase exchanger
H+ ATPase pump
Cl/HCO3- exchange to pump HCO3- into interstitium
Page 602
Collecting tubule principal cell
Site of aldosterone action - up regulates ENac expression -> increased Na+ absorption
ADH binds V2 receptor -> aquaporin channel put on lumenal side -> H2O resorption
Lithium inhibits aquaporin activity -> nephrogenic DI
Page 603
class of diuretics affecting principal cells
K+ sparing diuretics
Aldosterone antagonists - Spirolactone, eplerenone
Inhibit epithelial Na+ channels - triamterine, amiloride
Aldosterone effect on principal cells and intercalated cells
principal cells: reabsorption of Na+, secretion of K+
Intercalated cells: stimulates H+ secretion
