Distal tubule Flashcards
Function of distal tubule?
Fine tune and regulation ions
Separation Na+ from H2O
Dilution water- reabsorb Na+
What 2 cells found in distal tubule?
Principle
Intercalated
Function of principle cells?
Respond aldosterone- increase expression Na/K ATPase
Respond ADH (insertion AQP2- water reabsorbed)
What is ADH also known as?
Vasopressin
Function intercalated cells?
Exchange acids to bases
Vice versa
What are 2 types intercalated cells?
Alpha- secreted acid
Beta- secrete bicarb
Function of aldosterone?
Increase Na/KATPase pumps
Promote Na+ reabsorption
How is intracellular conc of Na+ kept low compared to lumen?
Why important?
Active transport Na+ via basolateral Na/K ATPase pump (3Na+ out, 2 K+ in)
Out of proximal tubule cell into interstitial fluid
Keep intracellular concentration of Na+ low compared to lumen (urine)
Allow Na+ moves down gradient into tubular epithelial cells
Allows continued Na+
Maintain conc gradient
Secondary transport of Na+ moves what?
Glucose and phosphate cotransported
Why does lumen of tubule become more acidic
H+ exchanged for Na+
Why is urine acidic?
Secreted H+
H2O and CO2 combine (carbonic anhydrase) to produce H+ and HCO3-
H+ is pumped into the lumen of urine by H ATPase and H/K counter transporter
K+ brought into cell
How does increased aldosterone effect sodium and potassium lvls?
Increase Na+ reabsorption and H2O
K+ lost due Na/K ATPase pump
When is aldosterone released (3)?
1.RAAS, sympathetic nerves, afferent arteriole wall tension, feedback, paracrine factors
2.Hyperkalaemia; causes the secretion of K+
3.Hyponatraemia; makes you retain Na+
What are effects aldosterone? (3)
1.Increases Na+ reabsorption in the distal tubule
2.Increases K+ secretion in the collecting duct
3.Increases proton secretion in the collecting duct
What stimulates release Atrial Natriuretic Peptide (ANP)?
1) Response stretch (large blood volume) caused by increase Na+
