Keeping the Brain Well Fed: The Role of Capillaries and Arterioles in Orchestrating Functional Hyperemia

Abstract

Cerebral blood flow increases in regions of increased brain activity. In this issue of Neuron, Rungta et al. (2018) characterize the contribution of different vascular compartments in generating this increase and outline the time course of arteriole and capillary dilation in generating functional hyperemia.

figure

Rungta et al divide the vasculature of the olfactory bulb into 4 compartments: (1) the pial arterioles, (2) the primary functional unit comprising the parenchymal (penetrating) arterioles and 1^st order capillaries, (3) the secondary functional unit comprising 1^st to 4^th order capillaries that are at least 50 μm removed from the parent arteriole, and (4) higher-order small-diameter capillaries, which are closest to the nerve terminals activated by olfactory stimuli. The pial and parenchymal arterioles are enveloped by a continuous layer of SMCs. Capillaries of the primary and secondary functional units are largely covered by enwrapping pericytes while higher-order capillaries are surrounded by thin-strand pericytes. Modified from Rungta et al.