NEURAL CONTROL OF SWALLOWING

ABSTRACT BACKGROUND: Swallowing is a motor process with several discordances and a very difficult neurophysiological study. Maybe that is the reason for the scarcity of papers about it. OBJECTIVE: It is to describe the chewing neural control and oral bolus qualification. A review the cranial nerves involved with swallowing and their relationship with the brainstem, cerebellum, base nuclei and cortex was made. METHODS: From the reviewed literature including personal researches and new observations, a consistent and necessary revision of concepts was made, not rarely conflicting. RESULTS AND CONCLUSION: Five different possibilities of the swallowing oral phase are described: nutritional voluntary, primary cortical, semiautomatic, subsequent gulps, and spontaneous. In relation to the neural control of the swallowing pharyngeal phase, the stimulus that triggers the pharyngeal phase is not the pharyngeal contact produced by the bolus passage, but the pharyngeal pressure distension, with or without contents. In nutritional swallowing, food and pressure are transferred, but in the primary cortical oral phase, only pressure is transferred, and the pharyngeal response is similar. The pharyngeal phase incorporates, as its functional part, the oral phase dynamics already in course. The pharyngeal phase starts by action of the pharyngeal plexus, composed of the glossopharyngeal (IX), vagus (X) and accessory (XI) nerves, with involvement of the trigeminal (V), facial (VII), glossopharyngeal (IX) and the hypoglossal (XII) nerves. The cervical plexus (C1, C2) and the hypoglossal nerve on each side form the ansa cervicalis, from where a pathway of cervical origin goes to the geniohyoid muscle, which acts in the elevation of the hyoid-laryngeal complex. We also appraise the neural control of the swallowing esophageal phase. Besides other hypotheses, we consider that it is possible that the longitudinal and circular muscular layers of the esophagus display, respectively, long-pitch and short-pitch spiral fibers. This morphology, associated with the concept of energy preservation, allows us to admit that the contraction of the longitudinal layer, by having a long-pitch spiral arrangement, would be able to widen the esophagus, diminishing the resistance to the flow, probably also by opening of the gastroesophageal transition. In this way, the circular layer, with its short-pitch spiral fibers, would propel the food downwards by sequential contraction

Coordination of respiration and swallowing: functional pattern and relevance of vocal folds closure

CONTEXT: Breathing and swallowing coordination, despite the expressive number of study, remain as theme deserving further research. OBJECTIVE: To identify a coordination pattern between swallowing and the natural breathing pause that occur in association with it (swallowing apnea) and also the relevance of the vocal folds closure in this process. METHODS: Sixty-six adults, male and female, including normal health people, post-laryngectomy individuals and patients with digestive complaints without dysphagia were analyzed. The respiratory air flux interruptions produced by wet requested swallows and dry, requested and spontaneous swallows, were registered using thermo and piezoelectric receptors coupled to synectics medical manometry equipment, using Polygram upper 4.21 software. The results were analyzed with the Chi-square (3×2) and (2×2) nonparametric independency test with P = 0.05. RESULTS: Swallowing apnea is a preventive breathing stop that start just before and stay present during all deglutition pharyngeal phase. It is a well coordinated phenomena that occur as pattern in association with low elastic resistance of the lung, on the expiratory final phase until inspiration initial phase. This breathing stoppage it is usually followed by a short expiraton preceding a new breathing cycle. The swallow apnea and vocal folds closure are both independents mechanisms. CONCLUSION: It is possible to suppose that in the subconscious condition, swallowing apnea is integrated under coordination of the same control mechanism that also involves the elastic resistance of the lung.<br>CONTEXTO: Apesar do expressivo número de estudos sobre a coordenação da respiração com a deglutição, o tema permanece aberto à pesquisa. OBJETIVO: Identificar um padrão de coordenação entre a pausa respiratória e a deglutição que ocorre em associação a esta usual apneia (apneia de deglutição) e estabelecer a importância do fechamento das pregas vocais que ocorre em associação a esta apneia. MÉTODOS: Foram estudados 66 adultos de ambos os sexos, incluindo voluntários sadios, indivíduos laringectomizados e pacientes com queixas digestivas sem disfagia. Apneias produzidas em associação com deglutições de liquido a pedido e deglutições a seco, solicitadas e espontâneas, foram registradas a partir de informações captadas por termo receptor e receptor piezelétrico acoplados a equipamento de manometria da Synectics Medical usando o software Polygran upper 4.21. Os resultados foram submetidos a teste de independência não paramétricos qui ao quadrado (3x2) e (2x2), com P = 0.05. RESULTADOS: A apneia de deglutição é uma pausa respiratória preventiva que se inicia imediatamente antes e permanece ativa durante toda a fase faríngea da deglutição. Esta apneia é um bem coordenado fenômeno padrão que ocorre em associação com a baixa resistência elástica dos pulmões, presentes nas fases final da expiração, até a inicial da inspiração. Esta pausa respiratória é usualmente seguida de uma curta expiração que antecede novo ciclo respiratório. A apneia de deglutição e o fechamento das pregas vocais são mecanismos independentes. CONCLUSÕES: É possível supor que em atividade subconsciente, a apneia de deglutição seja integrada sob a coordenação do mesmo mecanismo de controle que também envolve a resistência elástica dos pulmões