The deglutition act/swallowing reflex

Question: What is the importance of the deglutition act/swallowing reflex with regard to the regulation and feedback mechanisms of the stomatognathic system? Background The deglutition act represents one of the most frequent motor functional processes in our body, which coordinates more than 50 pairs of muscles. It can be understood as a complex reflux event. In the wake state, we swallow around 0.5–1.5 ml of saliva per minute, mostly unconsciously. During deep sleep, salivation and swallowing activities are largely at rest. In addition to regulating salivary flow, the deglutition act also appears to have an important influence on the regulatory and feedback mechanisms of the entire stomatognathic system. Since the lower jaw usually moves dorsally and the dental arches of the maxilla and mandible come into brief contact during the swallowing act [2, 4, 7], a physiological sequence of the swallowing activity is essential for controlling the masticatory muscles. During the physiological deglutition act, feedback is provided via the receptors in the periodontal attachment apparatus, as well as, those in the masticatory muscles and temporomandibular joint; this feedback is responsible for establishing impor¬tant control variables of the stomatognathic system, such as the rest position of the mandible when the masticatory muscles are relaxed. Each muscle works by shortening itself. However, a muscle which is constantly shortening (working) also requires information about what "length" it should maintain or set in the relaxed rest mode. Skeletal muscles, for example, use feedback from their direct antagonists' activity for establishing their "length" at rest; hence, an interplay between "flexors" and "extensors" is involved. In the stomatognathic system, this simple interplay as it occurs in the extremities is not so obvious. It is also necessary to consider that the stomatognathic system has to serve two functions. On the one hand, it performs the function of mastication, while on the other hand, it is a part of the organ of speech, so that, different centers in the brain – which partially compete with each other – exert their control functions on the stomatognathic system. In this manner, a "reset" through which the stomatognathic system always finds its physiological rest position represents a necessary set of rules for the undisturbed function of the stomatognathic system. The fact that the mandible can reliably and reproducibly be brought into the centric position during swallowing, and because this happens very frequently and unconsciously in the waking state, suggests that swallowing activity has an important control function. The occlusal contact which takes place between the upper and lower dental arches during the swallowing cycle generates a vertically acting force of approximately 30 N. The occlusal forces that are elicited during swallowing can modify the resulting force system. The force is thus not constant meaning that there is a continuous increase and decrease.