4 Tubular function 4 Flashcards
euvolemia
maintenance of normal ECF volume by balancing NaCl of exreted with ingested
clinical manifestations of excess sodium
Weight gain
Oedema formation – legs swollen, sock marks, changes in skin turgor
Hypertension
Nocturia
clinical manisfestations of sodium deficit
Weight loss
Changes in skin turgor
Syncope (fainting)
Orthostatic hypotension- drop in bp on standing, increased heart rate, dizzy, faint, tissue hypotension, death
what are the 2 major influences on Na+ excretion
GFR
tubular reabsorption of Na+ for fine control (collecting duct)
% sodium absorption at each part of tubule
PCT: 65-70%
thick ascending limb: 25%
DCT: 6%
Collecting duct: 1%
Effector mechanisms influencing renal Na+ transport
- renin-angiotensin-aldosterone system
- Sympathetic nervous system
- Atrial natriuretic peptide(s)
- Natriuretic factors
- Antidiuretic hormone (ADH)/ Vasopressin (minor)
RAAS influence on renal Na+ transport
AII influences proximal Na+ reabsorption (increases)
aldosterone influences late distal/ CCD Na+ reasborption (increases)
sympathetic nervous system influence of Na+ reabsorption
noradrenaline increases proximal Na+ reabsorption
activates RAAS
decreases GFR
ANP influence on renal Na+ transport
increases GFR (vasodilatation), inceased na+ excretion
decrease PCT and MCD Na+ reabsorption
inhibits aldosterone and renin release
natriuetic factors on renal Na+ transport
decrease proximal tubule Na+ reabsorption
inhibit renin release (increase Na+ excretion)
prostanoids can increase or decrease GFR
ADH influence of renal Na+ transport
inhibits RAAS
what is the juxtaglomerula apparatus
macula densa and granula cells
where is the site of renin release
granular cells
factors affecting renin release
low plasma Na+, ECF volume, BP-> stimulatory
high plasma Na+, ECF volume, BP-> inhibitory
macula densa mechanisms affecting renin release
decreased tubular [NaCl] delivery to distal tubule; Na K 2Cl cotransporter in macula densa cells
leads to increase renin release
