- is controlled almost entirely by local metabolic factors.
- exhibits autoregulation.
- exhibits active and reactive hyperemia.
- The most important local metabolic factors are hypoxia and adenosine.
- For example, increases in myocardial contractility are accompanied by an increased demand for 02. To meet this demand, compensatory vasodilation of coronary vessels occurs and, accordingly, both blood flow and 02 delivery to the contracting heart muscle increase (active hyperemia).
-During systole, mechanical compression of the coronary vessels reduces blood flow. After the period of occlusion, blood flow increases to repay the 02 debt (reactive hyperemia).
- Sympathetic nerves play a minor role.
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