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Integrated regulation of pressure and flow in the coronary microcirculation
J M Muller1, M J Davis, W M Chilian
1Department of Medical Physiology, Texas A and M, University Health Science Center, College Station, USA.
Insights
Coronary blood flow is regulated by various mechanisms, including metabolites and neurohumoral factors. Different vessel sizes have varying sensitivities, with integrated responses coordinating overall blood flow control.
Area of Science:
- Cardiovascular Physiology
- Vascular Biology
- Microcirculation Research
Background:
- Coronary blood flow regulation involves multiple interacting mechanisms.
- These include metabolic, myogenic, shear stress-mediated, and neurohumoral influences.
- Coronary arterioles of different sizes exhibit distinct sensitivities to these regulatory factors.
Purpose of the Study:
- To review the diverse regulatory mechanisms of coronary blood flow.
- To present a framework for integrating these mechanisms into a coordinated vascular response.
- To elucidate how different microvascular segments contribute to overall vasomotor tone.
Main Methods:
- This is a review article, synthesizing existing research.
- It discusses established physiological concepts and experimental findings.
- A conceptual framework for integration is proposed.
Main Results:
- Metabolites primarily influence smaller arterioles during hyperemia.
- Myogenic and metabolic mechanisms coordinate upstream microvessel tone.
- Neurohumoral factors modulate the extent of vasodilation.
Conclusions:
- Coronary blood flow regulation is a complex interplay of local and systemic factors.
- Different microvascular segments are controlled by distinct, yet integrated, mechanisms.
- Understanding this integration is key to comprehending coronary vasomotor control.
Abstract:
There are many mechanisms that contribute to the regulation of coronary blood flow including vasodilatory metabolites, myogenic regulation, flow- or shear stress-mediated vasodilation, and neurohumoral influences. It is interesting to note that coronary arterioles of varying sizes appear to possess different sensitivities to these regulatory factors, but each appears to dominate the control of a particular segment of the microvasculature. For example, during metabolic hyperemia the smallest arterioles seem to be most sensitive to the effects of metabolites, but metabolic and myogenic mechanisms that dictate the tone of upstream microvessels likely act in concert to facilitate the overall adjustments in coronary vasomotor tone. Neurohumoral mechanisms, seem to modulate the robustness of these intrinisic adjustments, perhaps by restraining the extent of vasodilation. The purpose of this review is to discuss these many regulatory mechanisms and also present a framework by which the vasoactive reactions elicited by these different mechanisms are integrated into coordinated responses of the entire coronary vascular network.