Autonomic Innervation of the Heart and Vasculature

The medulla, located in the brainstem, receives sensory input from different systemic and central receptors (e.g., baroreceptors and chemoreceptors) as well as signals from other brain regions (e.g., cerebral cortex and hypothalamus). Autonomic outflow from the brainstem is divided principally into sympathetic and parasympathetic (vagal) branches. Efferent fibers of these autonomic nerves travel to the heart and blood vessels where they modulate activity of these target organs. The S-A node is innervated by vagal (parasympathetic) and sympathetic fibers. Sympathetic efferent nerves are present throughout the atria (especially in the S-A node) and ventricles, and in the conduction system of the heart. Sympathetic nerves also travel to most arteries & veins. Parasympathetic fibers innervate blood vessels in certain organs such as salivary glands, gastrointestinal glands, and in genital erectile tissue.

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