Excretion is decreased by:
Excretion is increased by
ANP and prostaglandins.
1.1 Hormones Affecting Balance
1.2 Renin-Angiotensin System
Decreases sodium excretion by increasing aldosterone
Direct effect on proximal tubular epithelium
Renal vasoconstriction due to reduced medullary flow which increase medullary osmotic gradient and passive NA reabsorption in thin ascending limb
1.2.1 Direct Effects
Steroid from the adrenal cortex.
Increases Na reabsorption with K and H secretion.
Acts on principal cells of collecting ducts.
Immediate genomic effects to increase permeability to K
Stimulated by Angiotensin
A rise in plasma k very sensitive.
Afall in plasma NA
Atrial natriuretic peptide.
28 amino acids long
Produced in Atrail myocytes, available also as BNP and CNP
They react with receptors to produce effects such as
Natriuresis and diureis.
Lowers BP by causing vasodilation
Reduce smooth muscle responsiveness
Decrease levels of renin, aldosterone and AVP.
3 Potassium Balance
As potassium is the most prevalent cation.
Normalization is needed due to electrical polarisation and for normal intracellular function.
3.5 to 5.5 mmol/l are the ranges, any less or more is bad.
baklancStorage is due to physiology and pathophysiology.
Insulin, adrenaline and aldosterone enables the physiology to keep the balance balanced.
Pathophysiology: acid-base balance, plasma osmolality, cell lysis and exercise
3.1.1 Renal Handling
In the collecting duct, K is reabsorbed by intercalated duct and secreted by principal cells according to need.
3.2 4 Main determinants
A :concentration of K in the cytoplasm in principal cells
B: Conc of K in tubular fluid
C; Transepithelial Potential Difference
D: Permeability of luminal membrane to K
3.2.1 Factors influencing K secretion
Aldosterone A C D
K Intake A C Aldosterone
Distal Nephron Flow Rate B
Distal nephron Na delivery C and Flow rate
Impermeant anions Via C in tubular fluid
3.3 Systemic Acid-Base Status
In acute Alcalosis. K secretion increase. increase in pH makes it more permeable and hence secretion increase
While decrease, i.e acute acidosis K is retained.
Secretion increases due to inhibition of proximal reabsorption.