Vagal

Vagal is an adjective relating to the vagus nerve, the tenth cranial nerve, or to parasympathetic activity mediated by this nerve. The term derives from the Latin vagus, meaning wandering. In anatomy and physiology, vagal refers to structures or responses associated with the vagus nerve, which provides extensive innervation to the thorax and abdomen and forms a major component of the parasympathetic nervous system.

Anatomy: The vagus nerve begins in the medulla oblongata of the brainstem and exits the skull through the jugular foramen. It travels down the neck and into the thorax and abdomen, giving off branches to the heart, lungs, stomach, and other organs. Its long course enables widespread parasympathetic regulation across many organ systems.

Physiology: The vagus nerve provides parasympathetic innervation to the heart, affecting heart rate and conduction; to the lungs, influencing bronchial tone; and to the digestive tract, promoting motility, secretion, and pyloric relaxation. It also carries afferent sensory fibers conveying information about visceral status to the brain, enabling reflexes such as coughing, swallowing, and satiety signaling.

Vagal tone and heart rate variability: Vagal tone reflects baseline parasympathetic activity via the vagus and contributes to heart rate variability, a marker of autonomic flexibility. High vagal tone is associated with effective emotion regulation and adaptability, while low tone can accompany heightened stress reactivity and cardiovascular risk in some contexts.

Clinical relevance: Vagal maneuvers aim to increase vagal activity to influence heart rate and rhythm; they can terminate certain supraventricular tachycardias in some patients. Vagus nerve stimulation is used therapeutically for refractory epilepsy and, in some cases, depression. Vagal dysfunction can occur in autonomic disorders and contribute to dysmotility, syncope, or breathing irregularities.