1. Unit Four: The Circulation
Chapter 19: Role of the Kidneys in Long Term Control of Arterial Pressure and in Hypertension: The Integrated System for Arterial Pressure Regulation
Guyton and Hall, Textbook of Medical Physiology, 12 edition

2. Renal-Body Fluid System for Arterial Pressure Control
Quantitation of Pressure Diuresis as a Basis for
Arterial Pressure Control
Fig Typical renal urinary output curve showing pressure
diuresis when the arterial pressure rises above normal

3. Renal-Body Fluid System for Arterial Pressure Control
Demonstrating the Renal-Body Fluid System
Fig Increases in cardiac output, urinary output, and arterial
pressure caused by increased blood volume in dogs whose
nervous pressure control mechanisms have been blocked

4. Renal-Body Fluid System for Arterial Pressure Control
Arterial Pressure Control---”Near Infinite
Feedback Gain”
Fig Analysis of arterial pressure regulation by equating the “renal
output curve” with the “salt and water intake curve”

5. Renal-Body Fluid System for Arterial Pressure Control
Arterial Pressure Control---”Near Infinite
Feedback Gain”
The return of arterial pressure always back to
the equililbrium point is the near infinite
feedback gain principle for control of arterial
pressure by the renal-body fluid mechanism

6. Renal-Body Fluid System for Arterial Pressure Control
Two Determinants of the Long-Term Arterial
Pressure Level
The degree of pressure shift of the renal output
curve for water and salt
b. The level of water and salt intake

7. Fig. 19.4 Two ways in which the arterial pressure
can be increased:
A: by shifting the renal output curve
in the right hand direction toward a
higher pressure level
B: by increasing the intake level of salt
and water

8. Renal-Body Fluid System (cont.)
Chronic Renal Output Curve is Much Steeper
Than the Acute Curve
Fig. 19.5

9. Renal-Body Fluid System (cont.)
Failure of Increased Total Peripheral Resistance to
Elevate the Long-Term Level of Arterial Pressure
if Fluid Intake and Renal Function Do Not Change
Fig. 19.6

10. Renal-Body Fluid System (cont.)
Increased Fluid Volume Can Elevate Arterial Pressure
by Increasing Cardiac Output or Total Peripheral
Resistance
Fig. 19.7

11. Renal-Body Fluid System (cont.)
Importance of Salt in Renal-Body Fluid for Arterial
Pressure Regulation
When there is excess salt in ECF, the osmolality
increases and stimulates the thirst center
ultimately leading to an increase in ECF volume
Increase in osmolality stimulates the release of ADH
also leading to retention of fluid and increased ECF
volume

12. Renal-Body Fluid System (cont.)
Chronic Hypertension is Caused by Impaired Renal
Fluid Excretion
Mean arterial pressure (MAP) greater than 110 mm Hg
is hypertensive
Severe hypertension: MAP is mm Hg
If more than 50% above normal, a person will live
2-3 years without treatment

13. Renal-Body Fluid System (cont.)
Lethal effects of hypertension are caused in 3 ways
Excess workload on the heart leads to early heart
failure and coronary heart disease
Damage to a major blood vessel in the brain,
followed by death of parts of the brain (cerebral
infarct or stroke)
Injury to the kidneys producing renal destruction
and ultimately kidney failure, uremia, and death

14. Renin-Angiotensin System
Components of the Renin-Angiotensin System
Fig Renin-angiotensin vasoconstrictor
mechanism for arterial pressure
control

15. Renin-Angiotensin System
Rapidity and Intensity of the Vasoconstrictor Pressure Response to Renin-Angiotensin
Fig

16. Renin-Angiotensin System
Effect of Angiotensin II in the Kidneys- causes
retention of both salt and water in two ways:
Acts directly on the kidneys to cause salt and water retention
Causes the adrenal gland to secrete aldosterone, which causes the retention of
both salt and water
Mechanism of the Direct Effect of Angiotensin II

17. Renin-Angiotensin System
Large Variation in Salt Intake
Fig

18. Primary (Essential) Hypertension
Unknown Origin- characteristics cause by weight
gain and/or obesity
Cardiac output in increased
Sympathetic nerve activity, especially in the
kidney, is increased
Angiotensin II and aldosterone are increased 2-3
fold
d. Renal-pressure natriuresis is impaired

19. Primary (Essential) Hypertension
Graphic Analysis of Arterial Pressure Control in
Essential Hypertension
Fig

20. Primary (Essential) Hypertension
Treatment
Vasodilator drugs that increase renal blood flow
Natriuretic or diuretic drugs that decrease
tubular reabsorption of salt and water