Transcranial alternating current stimulation (tACS) at an appropriate dose shows encephalic effects, including neuronal stimulation and cerebral blood flow (CBF) responses. The mechanism of neurovascular coupling (NVC), where neurons communicate with vasculature to increase CBF, remains uncertain due to complex interactions with many parameters. Several vasoactive factors and pathways are involved in NVC. Thus, a robust mechanistic model of the NVU based on current understanding is necessary to study neuron-vasculature relationships. We developed a mathematical model from a multi-compartmental NVU model comprising the synaptic space, post-synaptic neurons, interneurons, astrocyte glial cells, perivascular space, and vascular smooth muscle. Total hemoglobin concentration (tHb) changes from optodes around tACS electrodes were fitted to linear models of six nested pathways. These pathways represent ion concentrations and transmembrane currents in various NVU components, providing insights into the effects of tACS on CBF.