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
Where is angiotensiongen located?
What enzyme converts angiotensin I into angiotensin II?
Located in the liver
ACE pathway
What does angiotensin II do? 7 things
vasoconstriction
Low BP
Low ECF
inc proximal Na+ uptake
sympathoexcitation - vasoconstriction and increased cardiac output
stimulates thirst mechanism to boost blood volume
stimulates ADH release
Where is aldosterone released from?
ZG, adrenal cortex
Where is ACE released from?
Lungs –> kidney–>ACE
Regulatory factors of RAA. What can ANP inhibit?
What can ADH inhibit?
What can stimulate renin release?
What increases aldosterone release?
ANP inhibits Aldosterone and renin
ADH inhibits renin
Renin is stimulated by macula densa, renal baroreceptor, catecholamines
Aldosterone increased by K+ and ACTH
