Renal 4. Integration of Salt and Water Balance Flashcards
What are the four ways to go about the integration of salt and water balance?
1) Renin-Angiotensin-Aldosterone Axis (RAAA)
2. Renal Sympathetic Nerve Activity
3. Arginine Vasopressin (AVP)
4. Atrial Natriuretic Peptide (ANP)
Renin-Angiotensin-Aldosterone Axis (RAAA)
1) liver produced angiotensinogen (inactive)
2) glomerular cells produce RENIN
(Triggered by blood pressure increase)
3) Renin converts angiotensinogen into angiotensin I
4) angiotensin I is converted to angiotensin II by ACE (produced by capillary endothelial cells)
5) angiotensin II go to adrenal cortex = releases ALDOSTERONE (increases blood pressure via Na+ reabsorption)
Renin Release triggers
- Decrease in systemic blood pressure (sympathetic effect on JGA)
- Decrease in NaCl concentration which is detected by the macula densa (NaCl sensor)
- Decrease in renal perfusion pressure
(Detected by renal baroreceptor)
How does angiotensin II increase blood pressure ?
Signals the adrenal gland = produces aldosterone = acts on the kidneys:
- DECREASE Na+ excretion
- DECREASE H2O excretion
What effect does aldosterone have on the kidney
1) DECREASE Na+ excretion/INCREASE Na+ reabsorption
2) DECREASE H2O excretion /
INCREASE H2O reabsorption
DECREASE Na+ excretion/INCREASE Na+ reabsorption causes?
Causes more Na+ in the blood = H2O follow = more H2O in blood = INCREASES blood pressure
DECREASE H2O excretion /
INCREASE H2O reabsorption causes?
Same thing as the other one .
Does angiotensin II upregulate anything, if so what is it?
YES, NHE (Na/H exchangers)
Why does angiotensin II upregulate Na+/H+ exchangers ?
To increase blood pressure
How does Na+/H+ exchangers allow angiotensin to increase blood pressure?
In the proximal convoluted tubule.
Acts directly on the Na+/H+ exchanger on the apical side of the principle cell = increase Na+ reabsorption = increases Na+ inside the cell = taken to the basolateral listed via Na+/K+ pump ——> into blood —-> trigger release of RENIN ——> angiotensin II increase blood pressure
How does aldosterone work?
Aldosterone released by adrenals glands, travels downstream, then attaches to cytotoxic receptor in principle cells within the distal tubule or collecting duct.
Where does aldosterone attach to
On cytosolic cells inside the distal or collecting tubule
where water reabsorption could occur
Once aldosterone attaches to Cytosolic receptors within the distal or collecting tubules, what does it do?
1) up regulate the Na/K ATPase pumps on the basolateral = increasing Na reabsorption and water will follow, = increasing blood volume = increasing blood pressure.
2) Upragulate both the Na and K channels on the apical membrane = reabsorb more Na from lumen into the cell and eventually into blood.
If you have to much aldosterone, patients will
pee out a lot of K+ ions.
What is another way to increase blood pressure by angiotensin II ?
Increase blood pressure = ANG II causes vasoconstriction of blood vessel = increases resistance = increases exterior pressure.
What could trigger a need to increase blood pressure?
A hemorrhage or loss of blood volume would cause blood pressure to decrease as well, and needs to be returned back to normal
- Renal Sympathetic Nerve Activity has both
Direct and indirect effects
- Renal Sympathetic Nerve Activity
Direct effects
- Increased renal vascular resistance = decreased RPF/GFR = increased Na+ retention in the blood
- Increased Na+ reabsorption by proximal tubule cells (increased NHE and Na-K Pump)
- Arginine Vasopressin (AVP)
Increased Plasma Osmolality Stimulates Osmoreceptors in the Hypothalamus to Trigger the Release of
Arginine Vasopressin, Which Inhibits Water
Excretion (ANTIDIERETIC)
Where does arginine vasopressin function to inhibit water excretion
On the thick ascending limb and the collecting tubules, through Na+
HOW does arginine vasopressin function to inhibit water excretion ?
It upregulates the Na/K/Cl co transports on the apical side of the THICK ascending limb and collecting tubule = Increases Na+ going through the cell and out into the blood. = this will causes H2O to follow it into the blood ——> reduce water excretion !
- Atrial Natriuretic Peptide (ANP)
Major effects are
hemodynamic:
- Atrial Natriuretic Peptide (ANP)
• Major effects are hemodynamic:
Renal vasodilation = increased blood flow:
How does ANP cause renal vasodilation = increased blood flow =
Decreases blood pressure
ANP is the only one that acts in
kidneys to reduced blood pressure when there’s an increase in blood pressure.
ANP released by the walls of the
atrial muscles.
What’s is ANP triggered by how is it released?
Triggered by an increase in blood pressure = walls of atrial muscles stretch = released ANP = renal vasodilation = increased blood flow (2 consequences)
What are the two 2 consequences of increasing blood flow via ANP?
- Increased GFR
2. Increase blood flow in vasa recta
- Increased GFR =
removing more Na out of the blood by filtering it, water follows = blood pressure decreases
- Increase blood flow in vasa recta =
washout the gradient in the medulla = around 800 mOsm instread of 1400 = less H2O reabsorbed = reducing blood volume = reducing blood pressure
- Renal Sympathetic Nerve Activity
Indirect Effect:
- Increase Renin release = increases blood pressure
