Tubular function 4 Flashcards
Define Euvolemia
maintenance of normal extracellular fluid volume, by balancing NaCl ingested with that excreted
Define natriuresis
Excretion of Na+ in urine
What are 2 major influences on Na+ secretion?
Where is most of the Na+ reabsorbed?
GFR
Tubular reabsorption of Na+ (collecting duct = fine control)
Bulk reabsorption in proximal tubule.
What are 5 effector mechanisms that influence renal Na+ transport?
- Renin-angiotensin-aldosterone system
- Sympathetic nervous system
- Atrial natriuretic peptides
- Natriuretic factors
- ADH/vasopressin
On which part does:
Angiotensin II?
Aldosterone act?
AII- proximal Na+ reabsorption
Aldosterone - late distal/CD Na+reabsorption
Does the RAA system increase or decrease blood Na+ levels?
increase
On which protein channels does Aldosterone act on?
Na/K pump, Na+ diffusion, K+secretion (principal cells) proton pump (intercalated cells)
How do the following systems influence Na+ transport? SNS? ANP? Natriuretic Factors? ADH?
SNS - increases Na+ reabsorption (noradrenaline and activates RAA)
ANP - can increase GFR but dec reabsorption and inhibits aldosterone and renin
NF- decreases, inhibits renin
ADH - inhibits RAA - decreases Na+
Where is Renin released from? Which cells?
Juxtaglomerular apparatus
granular cells release renin
What are 3 main mechanisms that stimulate the release of renin?
What compound do granular cells contain that allow for renin release?
- Macula densa (via NaCl)
- Renal baroreceptor
- Catecholamines
Contain prorenin
What transporter is involved in the macula densa mechanism?
NaCl - lack of triggers renin
Under what conditions are catecholamines released?
Fall in blood pressure stimulate beta-adrenoceptors
Under what conditions are baroreceptors triggered?
decrease in renal perfusion pressure
What 2 things can inhibit renin?
Angiotensin II and ADH
RAA system
What does renin act on?
Angiotensinogen to form angiotensin I
