Long-term blood pressure control by the kidney !
- Regulation
- Exam priority: medium
In the long run, blood pressure is set by the kidneys: if pressure rises, they excrete more salt and water until it comes back down.
Updated 2026-11-01
Also called: Pressure natriuresis
See it in 3D: Kidneys · Left renal artery · Right renal artery · Left adrenal gland
What it is
When arterial pressure rises, the kidney excretes more sodium and water (pressure natriuresis and diuresis); extracellular volume falls and pressure comes back. The equilibrium pressure is the one at which salt excretion equals intake. So for hypertension to persist, the kidney must need a higher pressure to excrete the salt being eaten.
How it works, step by step
- Arterial pressure rises for any reason.
- Peritubular capillary and renal interstitial pressure rise, and less sodium is reabsorbed in the proximal tubule.
- Renin is suppressed: angiotensin II and aldosterone fall, and the tubule keeps even less sodium.
- More sodium and water are excreted than are taken in.
- Extracellular volume, mean filling pressure and venous return fall.
- Cardiac output drops and, over time, tissue autoregulation lowers peripheral resistance too.
- Pressure settles back where excretion equals intake.
Equations
- CO
- cardiac output
- SVR
- systemic vascular resistance
The kidney does not change the formula; it changes volume, which moves output, and autoregulation then adjusts resistance.
Regulation
- +Angiotensin II: Constricts the efferent arteriole, boosts proximal sodium reabsorption and stimulates aldosterone: shifts the renal curve to higher pressures.
- +Aldosterone: Retains sodium in the collecting duct.
- +Renal sympathetic nerves: Release renin and increase sodium reabsorption.
- −Atrial natriuretic peptides: Raise filtration and sodium excretion when the atria are stretched.
- −Pressure natriuresis: Removes excess salt and water while pressure sits above the equilibrium point.
Clinical notes
- In chronic kidney disease nephrons are lost: more pressure is needed to excrete the same salt, and hypertension is almost the rule.
- Renal artery stenosis lowers the pressure the kidney "sees" and forces systemic pressure up so the salt gets excreted.
- Diuretics and salt restriction lower pressure because they work on this same volume balance.
Test yourself
Think of the answer, then tap the question to see it.
If a person with healthy kidneys is given a large volume load, why does pressure return to baseline within days?
High pressure raises sodium and water excretion (pressure natriuresis) until the extra volume is gone; balance returns to where excretion equals intake.
What must happen in the kidney for hypertension to persist?
The renal function curve must shift right: the kidney needs a higher pressure to excrete the salt being eaten.
Why does a person taking an ACE inhibitor become more salt-sensitive?
Without angiotensin II the kidney cannot tune sodium reabsorption to intake; the renal curve flattens and each change in salt moves pressure more.
Why do baroreceptors not set arterial pressure in the long term?
They reset within a day or two to the new pressure and stop opposing it; the lasting adjustment comes from the renal salt and water balance.
See it in 3D
The structures of Durgical's 3D anatomy where it happens.
Related topics
- The renin–angiotensin–aldosterone system
- Physiology of hypertension
- The baroreceptor reflex
- Nervous control of the circulation and the CNS ischemic response
- Venous return and the Guyton curves
Related conditions
In Biochemistry
In Pharmacology
Educational physiology content; not a diagnostic or treatment guide and no substitute for a health professional's advice. Values are approximate references. No doses are given.
Sources: 20.4 Homeostatic Regulation of the Vascular System (OpenStax (Rice University), 2022); Chronic Kidney Disease (StatPearls (NCBI Bookshelf), 2024); Essential Hypertension (StatPearls (NCBI Bookshelf), 2023); Hall JE. Guyton and Hall Textbook of Medical Physiology, 13th ed. (ch. 19). Reference book used to check facts; its text and figures are not reproduced (Elsevier, 2016).
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Representative model, for educational purposes only.