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[Physiology](https://durgical.com/en/physiology/) · [Cardiovascular](https://durgical.com/en/physiology/#s-cardio)

# Local and humoral control of blood flow

- Regulation
- Exam priority: medium

Each tissue adjusts its own arterioles to get the blood it needs, even when arterial pressure changes.

Updated 2026-11-01

Also called: Autoregulation of blood flow

**See it in 3D:** [Kidneys](https://durgical.com/en/anatomy/kidney/) · [Vessels inside the kidney](https://durgical.com/en/anatomy/intrarenal-arteries-and-veins/) · [Carotid arteries](https://durgical.com/en/anatomy/common-carotid-artery/)

## Key points

- Metabolic theory: adenosine, CO₂, H⁺, K⁺, lactate and falling O₂ dilate the arterioles of active tissue.
- Myogenic theory (Bayliss): when pressure stretches the wall, smooth muscle contracts and flow returns to its set value.
- Autoregulation roughly between ≈60–70 and ≈150–160 mmHg mean pressure in brain and kidney.
- The lung is the exception: alveolar hypoxia constricts its arterioles (hypoxic pulmonary vasoconstriction).
- Endothelium: nitric oxide and prostacyclin dilate; endothelin constricts. Endothelial dysfunction comes before atherosclerosis.

## What it is

Each organ's flow follows its metabolism: when a tissue works harder, its arterioles dilate. Many organs also hold flow nearly constant over a wide range of arterial pressure (autoregulation). On top of this local control, circulating substances constrict or dilate the vessels.

## How it works, step by step

- Active tissue uses more O₂ and makes more CO₂, H⁺, K⁺ and adenosine.
- These metabolites relax the smooth muscle of arterioles and precapillary sphincters.
- Local resistance falls and flow rises (active hyperemia) until the metabolites are washed out.
- If flow is cut off for a while, on release it overshoots well above normal (reactive hyperemia) and repays the oxygen debt.
- Higher flow raises shear stress on the endothelium, which releases nitric oxide and dilates the larger feeding arteries.
- In the long run, sustained ischemia drives the growth of new vessels and collaterals (angiogenesis).

## Regulation

- *+* **Local metabolites (adenosine, CO₂, H⁺, K⁺, lactate) and low PO₂**: Vasodilation of working tissue: more flow.
- *+* **Endothelial nitric oxide and prostacyclin**: Relax smooth muscle; sustain flow-mediated dilation.
- *+* **Bradykinin and histamine**: Dilate arterioles and raise capillary permeability (inflammation, anaphylaxis).
- *+* **Epinephrine at β2 receptors in skeletal muscle**: Muscle vasodilation at low physiological levels.
- *−* **Norepinephrine and epinephrine at α1 receptors**: Vasoconstriction of skin, viscera and kidney.
- *−* **Angiotensin II, vasopressin and endothelin**: Constrict arterioles and raise peripheral resistance.

## What controls flow in each organ

| Organ | Dominant control | Detail |
| --- | --- | --- |
| Heart | Metabolic (adenosine, low PO₂) | High O₂ extraction at rest: more demand needs more flow |
| Brain | CO₂ and H⁺; myogenic autoregulation | Hyperventilation lowers CO₂ and constricts cerebral vessels |
| Kidney | Myogenic and tubuloglomerular feedback | Keeps filtration steady |
| Skeletal muscle | Metabolic in exercise; sympathetic at rest | Flow can rise more than 20-fold |
| Lung | Alveolar hypoxia constricts | Diverts blood to well-ventilated alveoli |

## Clinical notes

- In peripheral artery disease the arterioles are already fully dilated: walking finds no flow reserve and claudication appears.
- In sepsis and anaphylaxis massive vasodilation wipes out peripheral resistance: distributive shock.
- In diabetic retinopathy the retinal capillaries lose autoregulation.

## Memory aid

"Whoever works asks for blood": active tissue opens its own gates with the waste of its work.

## Test yourself

Think of the answer, then tap the question to see it.

## Why does a muscle released from a tourniquet turn red and get more flow than normal?

During ischemia vasodilator metabolites build up and O₂ runs out; when flow returns the arterioles stay dilated (reactive hyperemia) until the oxygen debt is repaid.

## What keeps renal blood flow nearly unchanged when mean arterial pressure rises from 100 to 140 mmHg?

Autoregulation: wall stretch triggers myogenic contraction of the afferent arteriole, and tubuloglomerular feedback reinforces it.

## Why does hypoxia dilate systemic arterioles but constrict pulmonary ones?

In tissues hypoxia means poor supply and more flow fixes it; in the lung it means poorly ventilated alveoli, and constricting those vessels diverts blood to areas that do oxygenate.

## Why does a patient with peripheral artery disease hurt when walking but not at rest?

The stenosis caps maximal flow; at rest it is enough, but in exercise the arterioles are already dilated and there is no reserve for the extra demand.

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/physiology/local-and-humoral-control-of-blood-flow/)

## See it in 3D

The structures of Durgical's 3D anatomy where it happens.

- [Kidneys](https://durgical.com/en/anatomy/kidney/)
- [Vessels inside the kidney](https://durgical.com/en/anatomy/intrarenal-arteries-and-veins/)
- [Carotid arteries](https://durgical.com/en/anatomy/common-carotid-artery/)

## Related topics

- [Coronary circulation and myocardial ischemia](https://durgical.com/en/physiology/coronary-circulation-and-myocardial-ischemia/)
- [Skin blood flow](https://durgical.com/en/physiology/skin-blood-flow/)
- [Muscle blood flow and the cardiovascular response to exercise](https://durgical.com/en/physiology/muscle-blood-flow-and-the-cardiovascular-response-to-exercise/)
- [Nervous control of the circulation and the CNS ischemic response](https://durgical.com/en/physiology/nervous-control-of-the-circulation-and-the-cns-ischemic-response/)
- [Flow, pressure and resistance: Poiseuille and turbulent flow](https://durgical.com/en/physiology/flow-pressure-and-resistance-poiseuille-and-turbulent-flow/)
- [The renin–angiotensin–aldosterone system](https://durgical.com/en/physiology/the-renin-angiotensin-aldosterone-system/)

## Related conditions

- [Peripheral artery disease](https://durgical.com/en/conditions/peripheral-artery-disease/)
- [Acute limb ischaemia](https://durgical.com/en/conditions/acute-limb-ischaemia/)
- [Diabetic retinopathy](https://durgical.com/en/conditions/diabetic-retinopathy/)
- [Anaphylaxis](https://durgical.com/en/conditions/anaphylaxis/)
- [Sepsis and septic shock](https://durgical.com/en/conditions/sepsis-and-septic-shock/)

## In Biochemistry

- [Eicosanoids: prostaglandins, thromboxanes and leukotrienes](https://durgical.com/en/biochemistry/topics/eicosanoids-prostaglandins-thromboxanes-and-leukotrienes/)
- [Adrenaline](https://durgical.com/en/biochemistry/molecules/adrenaline/)
- [Angiotensin-converting enzyme (ACE)](https://durgical.com/en/biochemistry/enzymes/angiotensin-converting-enzyme/)
- [Lactate](https://durgical.com/en/biochemistry/molecules/lactate/)
- [ATP (adenosine triphosphate)](https://durgical.com/en/biochemistry/molecules/atp/)

## In Pharmacology

- [ACE inhibitors](https://durgical.com/en/pharmacology/classes/ace-inhibitors/)

[← All of physiology](https://durgical.com/en/physiology/)

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](https://openstax.org/books/anatomy-and-physiology-2e/pages/20-4-homeostatic-regulation-of-the-vascular-system) (OpenStax (Rice University), 2022); [20.2 Blood Flow, Blood Pressure, and Resistance](https://openstax.org/books/anatomy-and-physiology-2e/pages/20-2-blood-flow-blood-pressure-and-resistance) (OpenStax (Rice University), 2022); [Peripheral Arterial Disease](https://www.ncbi.nlm.nih.gov/books/NBK430745/) (StatPearls (NCBI Bookshelf), 2026); Hall JE. Guyton and Hall Textbook of Medical Physiology, 13th ed. (ch. 17). 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.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/physiology/local-and-humoral-control-of-blood-flow/