M. Bratzlavsky

Tooth pulpal reflexes in jaw musculature in man

Abstract Electrical stimulation of the tooth pulp elicited a short-latency, transient bilateral suppression of the voluntary masseter electromyogram. The threshold of this pulp reflex was somewhat higher than the pulpal sensory threshold, which coincided with the occurrence of a slight but distinct painful pricking sensation. When tested following pulp stimulation, the myotatic masseter reflex exhibited a phase of depression that had a much longer duration in resting conditions than during voluntary jaw closure. It is concluded that nociceptive afferents in the oro-facial area, most probably belonging to the A-delta group, have oligosynaptic inhibitory reflex connections with jaw-closing motoneurons.

Feedback control of human lip muscle

Abstract The human orbicularis oris reflex is most adequately evoked by a brief innocuous pressure stimulus applied to the lips. The reflex shows a strong potentiation 20 to 40 ms prior to and during voluntary lip muscle activation. Isometric orbicularis oris contractions very powerfully facilitate the reflex. It is suggested that in man the force-controlling properties of the lip musculature depend in part on the segmental afferent flow mediated through the lip reflex afferents.

Afferent influences upon human genioglossal muscle

SummaryAlthough extrinsic tongue muscles in man have been reported to contain muscle spindles, it has not been possible to record by electromyography any reflex response in the genioglossal muscle of healthy subjects upon stretching the tongue or upon electrical stimulation of the hypoglossal nerve. Neither could a silent period be evoked in the muscle following its twitch contraction. Nociceptive stimulation of the tongue mucosa during tongue protrusion elicited a crossed inhibitory reflex response in the genioglossal muscle. This reflex, conveyed centrally through the lingual nerve, could be involved in the prevention of tongue injuries during mastication.ZusammenfassungEs wird berichtet, daß die Zungenmuskulatur des Menschen Muskelspindeln enthält. Dennoch war es am Normalen nicht möglich, elektromyographisch eine Reflexantwort im Musculus genioglossus nach Strecken der Zunge oder elektrischer Reizung des Nervus hypoglossus zu erhalten. Auch konnte in diesem Muskel nach Kontraktion infolge Nervenreizung keine silent period nachgewiesen werden. Nocizeptive Reize der Zungenschleimhaut während des Herausstreckens der Zunge bewirkten gekreuzte Hemmreflexe im M. genioglossus. Diese Reflexe wurden durch den N. lingualis zentripetal geleitet und können eine Rolle beim Verhindern von Zungenverletzungen während des Kauaktes spielen.

Reciprocal innervation of motoneurons lacking Ia input in man.

Abstract A clear pattern of reciprocal innervation was found among the orbicularis oculi and the frontalis muscles in man during voluntary contractions. In contrast, facial afferent input was shown to be devoid of reciprocal action on these muscles. The results indicate a lack of γ control in facial muscles.