Studies of the local intrinsic cardiac nervous system have revealed its significance and complexity, but yielding so far a fragmented picture that leaves gaps that cannot be addressed by experiments alone towards functional predictions for control of the system. Prior modeling efforts, including our own, have had to work within these limitations. Recently the SPARC initiative has supported comprehensive study of the ICN to provide foundational data to allow modeling that supports functional prediction and control more feasible. These rich datasets on ICN are cross species (rat and pig), include male and female, and have multiple replicates to account for variability and uncertainties including off target effects. The unmet need now is to build on the opportunity for an integrative multiscale model (MSM) of the circuit to integrate this patchwork into a functional whole foundational to determining control points for interventions. The MSM will provide quantitative and dynamic accounting of the signal processing and adaptation dynamics of this local nervous system intrinsic to the heart. The newly available foundational neuroanatomical, physiological and molecular information on the ICN now support MSM to scale single neuron and molecular phenotype data to have ICN networks and cardiac functional impact. We will use MSM modeling to close the gap between these data and ICN functions, supporting exploration of how this system drives cardiac dynamics. This will enable our simulations to predict organ-scale functional consequences of vagal neurostimulation with high fidelity, immediately opening avenues for in silico testing and in vivo and clinical confirmation of neuromodulatory control algorithms.