The number and size of nerve fibres to the masticatory muscles of the horse

Murphy, Thomas R.; Cameron, Hugh U.

doi:10.1016/0003-9969(67)90064-7

Cited by 6 publications

(1 citation statement)

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“…Jaw-closing muscles, the masseter and the temporalis, are reported to contain many muscle spindles (FREIMANN, 1954;COOPER, 1960;HOSOKAWA, 1961;KARL-SEN, 1969;KUBOTA, 1974), while jaw-opening muscles have very few, if any (Tin-LANDER, 1964;MURPHY and CAMERON, 1967;KAWAMURA, 1974). In this study, likewise, cortical potentials evoked by stimulation of a jaw-opening muscle, the anterior belly of the digastric muscle, could be recorded very rarely.…”

Section: Methodsmentioning

confidence: 99%

A Study of Sensory Projection from Jaw Muscles to the Cerebral Cortex in the Rat

Abe

1978

Jpn.J.Physiol

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The sensory projection from jaw muscles to the cerebral cortex have been studied in rats by electrophysiological and histochemical methods. Electrical stimulation of individual masticatory muscles elicited bilateral responses in the cortical areas 8, 10, 2, and 2a. The following pathway was postulated to mediate these cortical responses; impulses of muscle origin are conducted in turn to the trigeminal mesencephalic tract nucleus (TMT), the contralateral thalamic nucleus ventralis posteromedialis (VPM), the cerebral cortex and finally to the other cerebral cortex which is ipsilateral to the side of stimulation. The ipsilateral cortical response appeared about 5 msec later than the contralateral one and was abolished by sectioning the corpus callosum. By stimulating the cerebral cortex antidromically, the conduction time to the VPM was found to be as long as 6 msec. The conduction from the TMT to the contralateral VPM consumed a period of more than 10 msec. It was presumed to be multisynaptic, being based on the finding that horseradish peroxidase injected into the VPM could not be recovered in the contralateral TMT.Only a few studies have been made on the sensory input to the cerebral cortex which eventually lead to masticatory and swallowing movements. For example, in 1974, LUND and SESSLE reported that group I jaw muscle afferents projected to the cortex of the cat, but the neural pathway was not fully investigated. Futhermore, concerning the function of the feedback loop in masticatory movements, there are two contradictory viewpoints, i.e., i) suprasegmentally evoked chewing movements are not directly affected by information from the periphery ; ii) the suprasegmental center strongly interacts with the feedback from the periphery LUND and SESSLE, 1974;MORIMOTO and KAWAMURA, 1973). The study of the neural control mechanism of masticatory movements seems to be essential.In the rat, the electrophysiological study of the neural path between the masticatory muscle and the cortex has not been made. To understand the neural

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Section: Methodsmentioning

confidence: 99%

A Study of Sensory Projection from Jaw Muscles to the Cerebral Cortex in the Rat

Abe

1978

Jpn.J.Physiol

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Proprioceptive afferents in facial nerves of some insectivores

Kubota

Masegi

1972

Anat. Rec.

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Fiber-caliber analysis of the facial nerve was made in the Japanese lesser shrew-mole and the Japanese shrew-mole possessing muscle spindles in the snout muscles and in the shinto shrew with no spindles. Using an enlarged photographic scale ( x 250) prepared from the object-micrometer (1/100 mm), the measurement of the fiber-caliber was made on the enlarged photograph ( X 1250) of the cross paraffin section treated with a modified myelin-sheath staining procedure by Pettersen et al. ('70). The facial nerves of the shrew-moles contained fibres of 1 to 10 p in diameter, while the facial nerve of the shrew consisted of fibers of 1 to 6 p . The spectra of the former have a slight bimodality with the highest peak at 2 P and smaller one at 6 P. The spectrum of the latter has a unimodality with a greater peak at 2 r . Each peak revealed a log-normal distribution curve. Statistically, it can be said that there is a significant difference in the caliber-spectra between the facial nerves supplying the snout muscles with muscle spindles and without spindles.For testing whether the skew of the spectrum can be the result of a truly bimodal distribution, the left facial nerve of the Japanese shrew-moles was cut at the site beneath the auditory capsule. Complete degeneration of spindle innervation in the snout muscles was observed histologically in animals seven days after operation.

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