I’m using this picture to point out scattering barriers, to current flow, that we must consider when electrical stimuli are applied to neural tissues via tissue encapsulated electrodes. Here are the encapsulation tissues. Here I point out the perineurium, a tight cell layer forming around a bundle of nerve fibers we call a fascial. The perineurium is an extension of the dura surrounding the central nervous system. Finally, the epineurium, a compact layer of cells surrounding the bundled fascials that form the peripheral nerve.
Donald G. Atzberger, “Tissue Response to Implanted Self-Sizing Spiral Cuff, MS Thesis, CWRU, Departments of Chemical Engineering and Biomedical Engineering, 1998.