From the Guidelines
The cranial nerve nuclei providing parasympathetic input to the heart are the dorsal motor nucleus of the vagus nerve and the nucleus ambiguus, as evidenced by recent studies on the neuropsychobiology of fear-induced bradycardia in humans 1. These nuclei are located in the medulla oblongata of the brainstem and contain preganglionic parasympathetic neurons that send fibers through the vagus nerve to the heart.
- The dorsal motor nucleus of the vagus nerve is responsible for regulating various autonomic functions, including heart rate and digestion.
- The nucleus ambiguus, on the other hand, contributes to the control of heart rate and other cardiac functions, working in conjunction with the dorsal motor nucleus to provide comprehensive parasympathetic regulation of cardiac function 1. The parasympathetic fibers released by these nuclei synapse with postganglionic neurons located in cardiac ganglia near or within the heart itself, releasing acetylcholine, which binds to muscarinic receptors on cardiac tissue, resulting in decreased heart rate, reduced conduction velocity, and decreased contractility 1. This parasympathetic control serves as the primary mechanism for reducing cardiac output and is essential for maintaining normal heart function, especially during rest, as supported by the neurovisceral integration model 1.
From the Research
Cranial Nerve Nuclei Providing Parasympathetic Input to the Heart
- The dorsal motor nucleus of the vagus nerve (DMV) is a key structure involved in the parasympathetic control of various visceral functions, including heart rate regulation 2, 3, 4, 5, 6.
- Studies have shown that the DMV is subdivided into distinct subnuclei, each with specific cytoarchitectonic and chemoarchitectonic characteristics 2.
- The DMV receives inputs from various sources and sends outputs to different visceral organs, including the heart, via the vagus nerve 3, 6.
- The development of the human DMV has been studied, and it has been shown that the nucleus emerges as a distinct structure with multiple subnuclei by 13-15 weeks of gestation 5.
- Functional maturation of the DMV occurs in parallel with the development of cardiovascular and gastric movements, suggesting a role for the DMV in regulating these functions 5.
- Stimulation of specific areas within the DMV can evoke simultaneous changes in crural diaphragm activity, lower esophageal sphincter pressure, and fundus tone, indicating a coordinated control of visceral functions by the DMV 6.
- The DMV is not the only source of visceromotor fibers, and other cranial nerve nuclei may also contribute to parasympathetic input to the heart 4.