Regulation of blood flow in the microcirculation. 2005

Steven S Segal
The John B. Pierce Laboratory & Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT 06519, USA. sssegal@jbpierce.org

The regulation of blood flow has rich history of investigation and is exemplified in exercising skeletal muscle by a concerted interaction between striated muscle fibers and their microvascular supply. This review considers blood flow control in light of the regulation of capillary perfusion by and among terminal arterioles, the distribution of blood flow in arteriolar networks according to metabolic and hemodynamic feedback from active muscle fibers, and the balance between peak muscle blood flow and arterial blood pressure governed by sympathetic nerve activity. As metabolic demand increases,the locus of regulating oxygen delivery to muscle fibers "ascends" from terminal arterioles, through intermediate distributing arterioles, and into the proximal arterioles and feed arteries, which govern total flow into a muscle. At multiple levels, venules are positioned to provide feedback to nearby arterioles regarding the metabolic state of the tissue through the convection, production and diffusion of vasodilator stimuli. Electrical signals initiated on microvascular smooth muscle and endothelial cells can travel rapidly for millimeters through cell-to-cell conduction via gap junction channels, rapidly coordinating vasodilator responses that govern the distribution and magnitude of blood flow to active muscle fibers. Sympathetic constriction of proximal arterioles and feed arteries can restrict functional hyperemia while dilation prevails in distal arterioles to promote oxygen extraction. With vasomotor tone reflecting myogenic contraction of smooth muscle cells modulated by shear stress on the endothelium, the initiation of functional vasodilation and its modulation by sympathetic innervation dictate how and where blood flow is distributed in response to metabolic demand. A remarkable ensemble of signaling pathways underlies the integration of smooth muscle and endothelial cell function in microvascular networks. These pathways are being defined with refreshing new insight as novel approaches are applied to understanding the cellular and molecular mechanisms of blood flow control.

UI MeSH Term Description Entries
D008833 Microcirculation The circulation of the BLOOD through the MICROVASCULAR NETWORK. Microvascular Blood Flow,Microvascular Circulation,Blood Flow, Microvascular,Circulation, Microvascular,Flow, Microvascular Blood,Microvascular Blood Flows,Microvascular Circulations
D010100 Oxygen An element with atomic symbol O, atomic number 8, and atomic weight [15.99903; 15.99977]. It is the most abundant element on earth and essential for respiration. Dioxygen,Oxygen-16,Oxygen 16
D001783 Blood Flow Velocity A value equal to the total volume flow divided by the cross-sectional area of the vascular bed. Blood Flow Velocities,Flow Velocities, Blood,Flow Velocity, Blood,Velocities, Blood Flow,Velocity, Blood Flow
D001794 Blood Pressure PRESSURE of the BLOOD on the ARTERIES and other BLOOD VESSELS. Systolic Pressure,Diastolic Pressure,Pulse Pressure,Pressure, Blood,Pressure, Diastolic,Pressure, Pulse,Pressure, Systolic,Pressures, Systolic
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D014666 Vasomotor System The neural systems which act on VASCULAR SMOOTH MUSCLE to control blood vessel diameter. The major neural control is through the sympathetic nervous system. System, Vasomotor,Systems, Vasomotor,Vasomotor Systems

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