Dynamic cardiovascular control supports adaptive behavior under external and internal influences. Higher-order brain regions regulate stress-related cardiovascular changes via their influence on medullary nuclei, which control autonomic reflexes. Despite extensive research, the precise neural circuits linking cardiac function and behavior under emotional stress remain unclear. This review highlights recent studies identifying specific cell types and pathways involved in cardiovascular regulation, emphasizing their dynamical role under baseline and threat conditions. Cardiovascular responses are closely tied to behavior through descending brain-to-heart command pathways and ascending interoceptive feedback. Our framework for characterizing cardio-behavioral states under threat identifies rapid-acting “microstates” and slow-changing “macrostates” reflecting context- and time-dependent threat levels. Multidimensional measurements and integrated analytical approaches are required to study neural circuits controlling cardio-behavioral states. Understanding the homeodynamic regulation of cardiac function and its behavioral links is essential for unraveling brain-heart interactions.