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Fig. 4 | Fluids and Barriers of the CNS

Fig. 4

From: Functional hyperemia drives fluid exchange in the paravascular space

Fig. 4

Functional hyperemia-driven flow in the PVS in an arteriolar-brain model with realistic mechanical properties. Note the geometry is depicted with an unequal aspect ratio in the radial (r) and axial (z) directions for viewing convenience. a Plot of the prescribed arteriolar wall movement for functional hyperemia. All the other boundary conditions used in this simulation are similar to the ones shown in Fig. 3a. b Contours showing the axial velocity (velocity in the z-direction) in a cross section of the PVS, when the arteriolar wall movement is given by a typical neural activity-driven vasodilation response. The boundary conditions (shown in the left panel) for this simulation are the same as the ones shown in Fig. 3. Compared to heartbeat-driven pulsations (Fig. 3c), vasodilation-driven fluid flow occurs through the entire length of the PVS and has substantially higher flow velocities. The model also predicts that the vasodilation can also cause significant deformation in the brain tissue. A portion of the vessel lumen is shown in red to provide a sense of vasodilation. These calculations were performed with fluid permeability, ks = 2 × 10−14 m2 and tissue shear modulus µs = 4 kPa

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