3. Long term regulation of Blood Pressure
Nervous mechanisms are not capable of maintaining long term homeostasis
Nervous system resets to new state----Receptor adaptation
Long term regulation of BP is through:
1. Body fluid control
2. Balance between intake and out put of fluid and salts
Regulation of arterial pressure is primarily by conserving or excreting salts and water from circulation via the kidneys to
maintain Normal blood volume

4. Renal body fluid system
↑ECF → ↑blood volume → ↑Blood pressure → ↑Urinary out put of salt and water (Kidneys simply excrete extra volume of Fluid responsible for ↑Blood pressure )
↓ECF → ↓blood volume → ↓Blood pressure → ↓ urinary out put of salt and water (Retention of salt and water)

5. Renal body fluid system
A few mm Hg rise in arterial pressure
→ ↑ ↑ Urinary water loss (Pressure diuresis)
→ ↑ ↑ Urinary Na (Pressure Natriuresis)

6. Pressure Diuresis (Renal output curve)
At 50 mm Hg-
No urine output
At100 mm Hg Normal urine Vol.
200 mm Hg
7-8 times urine output
Renal function curve or
Renal urinary out put curve

7. Effects of addition of Extra fluid
Nervous receptors blocked
Infusion of 400 ml blood
↑ blood volume
↑ COP
↑ Arterial pressure
↑ Urinary out put
Water excreted till the restoration of normal levels

9. Near infinite feed back Gain principle
150 mm Hg
More loss of water and salts than intake
Till equilibrium
80 mm Hg
Intake of salt and water more than out put

10. Effect of altered Renal out put curve (ROC)
ROC shifted to higher pressure side
Salt and water intake normal
Equilibrium point shifted to 150 mm Hg
Arterial pressure will be maintained at 150 mm Hg

11. Effect of change in salt and water intake
ROC normal
Increased level of salt and water intake
Equilibrium point shifted to Higher pressure side
(160 mm Hg)
Arterial pressure will be maintained at mm Hg

12. Two basic determinants of long term arterial pressure are
The level of salt and water intake
The degree of shift of the renal function curve along the pressure axis.

13. Important Excess pure water intake does not maintain elevated pressure
It is very quickly excreted in the urine
ADH mechanism
Excess salt intake is more important for long term elevation of arterial pressure

14. Renin angiotensin system
Besides controlling body fluid volume
Kidneys also contribute in BP homeostasis through Renin angiotensin system
Fall in pressure cause production of Renin from the kidneys
Renin is a protein enzyme produces from JG cells
Renin has multiple ways to control BP

15. Juxtaglomerular apparatus

16. Effects of Angiotensin II
Angiotensin II acts directly on the kidneys to cause salt and water reabsorption
Indirectly increases the secretion of aldosterone by adrenal glands.

17. Importance of vasoconstrictor effect of Angiotensin after hemorrhage
BACK

18. Effects of angiotensin on ROC
Angiotensin shifts the ROC to High pressure level Equilibrium point moves to higher pressure level
Next

19. Angiotensin maintains Normal BP
Angiotensin maintains normal blood pressure despite variations in salt intake
↑ salt intake →↑ECF volume →↑BP → ↑ blood flow in the kidneys →↓Renin →↓Angiotensin→ ↓renal retention of salt and water → ↓BP
↓ salt intake →↓ECF volume →↓BP → ↓ blood flow in the kidneys →↑Renin →↑Angiotensin→ ↑renal retention of salt and water → ↑BP