Activity of the Digastric Muscle in Swallowing and Chewing

Munro, R. R.

doi:10.1177/00220345740530030401

Cited by 24 publications

(17 citation statements)

References 15 publications

(3 reference statements)

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“…Electromyographic data nevertheless confirm that there is synchronized activity in the two bellies during all mandibular movements, chewing, and swallowing (Munro, 1972;Munro, 1974;Yemm, 1977). Munro (1974) and Widmalm etal. (1987) both reported that occasionally activity can be nonsynchronous, but it is hard to postulate how this translates into any functional advantage other than selective control over the hyoid bone.…”

Section: Digastricmentioning

confidence: 72%

“…In practice, this is quite difficult to confirm because electrodes must be inserted with precision into both bellies, and it has not been attempted often. Electromyographic data nevertheless confirm that there is synchronized activity in the two bellies during all mandibular movements, chewing, and swallowing (Munro, 1972;Munro, 1974;Yemm, 1977). Munro (1974) and Widmalm etal.…”

Section: Digastricmentioning

confidence: 73%

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Internal Organization in the Human Jaw Muscles

Hannam

McMillan

1994

Critical Reviews in Oral Biology & Medicine

154

102

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The human jaw muscles are essential to mastication and play an important part in craniofacial growth. They contribute to dental and articular forces, deform the mandible, and, like other tissues, are subject to disorders, often manifested as pain. The literature describes how their contraction is controlled by the nervous system, and how their general structure and function contribute to craniofacial biology, but there has been little appraisal of their internal organization. Most of these muscles are not simple; they are multipennate, complexly layered, and divided by aponeuroses. This arrangement provides substantial means for differential contraction. In many ways, jaw muscle fibers are intrinsically dissimilar from those found in other skeletal muscles, because they are arranged in homogeneous clusters and generally reveal type I or type II histochemical profiles. Most are type I and are distributed preferentially in the anterior and deeper parts of the jaw closers. Additionally, most motor unit (MU) territories are smaller than those in the limbs. There is circumstantial evidence for intramuscular partitioning based in part on innervation by primary muscle nerve branches. During normal function. MU recruitment and the rate coding of MU firing in human jaw muscles follow the general principles established for the limbs, but even here they differ in important respects. Jaw muscle MUs do not have stable force recruitment thresholds and seem to rely more on rate coding than on sequential unit recruitment to grade the amplitude of muscle contraction. Unlike those in the limbs, their twitch tensions correlate weakly with MU fatiguability and contraction speed, probably because there are so few slow, fatigue-resistant MUs in the jaw muscles. Moreover, the type I fibers that are present in such large numbers do not contract as slowly as normally expected. To complicate matters, estimation of jaw MU twitch tensions is extremely difficult, because it is affected by the location used to measure the twitch, the background firing rate, muscle coactivation, and regional, intramuscular mechanics. Finally, there have been very few systematic studies of jaw MU reflex behavior. The most recent have concentrated on exteroceptive suppression and suggest that MU inhibition following intra- and perioral stimulation depends on the location of the MU, its background firing rate, the timing of the stimulus, and the task used to drive the unit. Task dependency is a common feature of human jaw MU behavior, reflecting interaction between peripheral sensory information from orofacial and muscle afferents and corticobulbar drive.(ABSTRACT TRUNCATED AT 400 WORDS)

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Section: Digastricmentioning

confidence: 72%

Section: Digastricmentioning

confidence: 73%

Internal Organization in the Human Jaw Muscles

Hannam

McMillan

1994

Critical Reviews in Oral Biology & Medicine

154

102

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“…Our study discovered that axon collaterals from labeled genioglossus premotor neurons also innervate MoV motoneurons supplying the jaw-opening anterior digastric muscles, as well as the motoneurons located in the central part of the MoVII. The central MoVII supplies the posterior digastric muscle (jaw-opening and swallowing), the platysma muscle (which depresses the jaw and draws down the lower lip), and the lower lip muscle (Munro, 1974; Ashwell, 1982; Hinrichsen and Watson, 1984), which are all activated when the tongue is protruding (Figure 5). Additionally, we found that axon collaterals from labeled masseter premotor neurons also innervate motoneurons located in the dorsal MoXII, previously shown to innervate tongue-retractor muscles (McClung and Goldberg, 1999).…”

Section: Discussionmentioning

confidence: 99%

Monosynaptic premotor circuit tracing reveals neural substrates for oro-motor coordination

Stanek

Cheng

Takatoh

et al. 2014

eLife

104

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Feeding behaviors require intricately coordinated activation among the muscles of the jaw, tongue, and face, but the neural anatomical substrates underlying such coordination remain unclear. In this study, we investigate whether the premotor circuitry of jaw and tongue motoneurons contain elements for coordination. Using a modified monosynaptic rabies virus-based transsynaptic tracing strategy, we systematically mapped premotor neurons for the jaw-closing masseter muscle and the tongue-protruding genioglossus muscle. The maps revealed that the two groups of premotor neurons are distributed in regions implicated in rhythmogenesis, descending motor control, and sensory feedback. Importantly, we discovered several premotor connection configurations that are ideally suited for coordinating bilaterally symmetric jaw movements, and for enabling co-activation of specific jaw, tongue, and facial muscles. Our findings suggest that shared premotor neurons that form specific multi-target connections with selected motoneurons are a simple and general solution to the problem of orofacial coordination.DOI: http://dx.doi.org/10.7554/eLife.02511.001

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“…Electrodes were positioned using techniques previously described by others [ 18,19,20,21] and tested in cadavers by us. Two electrodes, 1 cm apart, were placed in each muscle.…”

Section: Data Collection Electromyography (Emg)mentioning

confidence: 99%

Coordination of mastication and swallowing

et al. 1992

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The coordination of mastication, oral transport, and swallowing was examined during intake of solids and liquids in four normal subjects. Videofluorography (VFG) and electromyography (EMG) were recorded simultaneously while subjects consumed barium-impregnated foods. Intramuscular electrodes were inserted in the masseter, suprahyoid, and infrahyoid muscles. Ninety-four swallows were analyzed frame-by-frame for timing of bolus transport, swallowing, and phases of the masticatory gape cycle. Barium entered the pharynx a mean of 1.1 s (range -0.3 to 6.4 s) before swallow onset. This interval varied significantly among foods and was shortest for liquids. A bolus of food reached the valleculae prior to swallow onset in 37% of sequences, but most of the food was in the oral cavity at the onset of swallowing. Nearly all swallows started during the intercuspal (minimum gape) phase of the masticatory cycle. Selected sequences were analyzed further by computer, using an analog-to-digital convertor (for EMG) and frame grabber (for VFG). When subjects chewed solid food, there were loosley linked cycles of jaw and hyoid motion. A preswallow bolus of chewed food was transported from the oral cavity to the oropharynx by protraction (movement forward and upward) of the tongue and hyoid bone. The tongue compressed the food against the palate and squeezed a portion into the pharynx one or more cycles prior to swallowing. This protraction was produced by contraction of the geniohyoid and anterior digastric muscles, and occurred during the intercuspal (minimum gape) and opening phases of the masticatory cycle. The mechanism of preswallow transport was highly similar to the oral phase of swallowing. Alternation of jaw adductor and abductor activity during mastication provided a framework for integration of chewing, transport, and swallowing.

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Activity of the Digastric Muscle in Swallowing and Chewing

Abstract: Electromyographic investigation indicates that the two bellies of the digastric muscle contract simultaneously in swallowing and in the open phase of chewing. However, about the time of tooth contact in chewing the posterior belly is active, while the anterior belly usually is inactive.

Cited by 24 publications

References 15 publications

Internal Organization in the Human Jaw Muscles

Internal Organization in the Human Jaw Muscles

Monosynaptic premotor circuit tracing reveals neural substrates for oro-motor coordination

Coordination of mastication and swallowing

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