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From the Research
Function of the Nucleus Ambiguus
The nucleus ambiguus (NA) is a complex structure in the medulla oblongata that plays a crucial role in various physiological functions, including:
- Control of laryngeal, pharyngeal, and esophageal muscles 1
- Regulation of respiration, swallowing, and vocalization 1, 2
- Parasympathetic control of cardiorespiratory functions 3
- Motor control of the upper airways and striated esophagus 3
Subdivisions and Projections
The NA can be differentiated into three main subdivisions, each with distinct morphology, distribution, and physiological function of their neurons 2. The NA receives afferent projections from various brain regions, including the medial parabrachial and Kölliker-Fuse nuclei, and the lateral nucleus of the solitary tract 2.
Neuronal Activity and Function
Studies have shown that NA neurons are active during various behaviors, including:
- Vocalization: laryngeal motoneurons (MNs) become active 100-200 ms before vocalization and cease discharging during or immediately after vocalization 1
- Swallowing: some MNs and non-MNs are active during swallowing 1
- Respiration: some MNs and non-MNs are active during respiration 1, 4
- Cardiovascular regulation: a subset of NA neurons innervates the heart through the vagus nerve to control cardiac function at rest and during key autonomic reflexes 3
Clinical Significance
Lesions or damage to the NA have been implicated in various clinical conditions, including:
- Vocal cord abductor paralysis: selective neurogenic atrophy of the posterior cricoarytenoid muscles has been observed in cases of multiple system atrophy presenting with vocal cord abductor paralysis 5
- Neurogenic hypertension: lesion of the NA can facilitate hypertension produced by sinoaortic deafferentation 4