下顎舌反射誘発に関与する側頭筋の固有受容器
1988 年 55 巻 3 号 p. 460-470
詳細
1988 年 55 巻 3 号 p. 460-470
Passive depression of the lower jaw reflexively evokes the extrinsic tongue muscle EMG activity. This reflex is called the jaw-tongue reflex (JTR) and was reported to be evoked by the afferents from the temporal muscle (TM) . The present study was carried out to determine which types of proprioceptors in the TM could evoke the JTR in the chloralose-anesthetized cats, with the following results: (1) Isometric contraction of the tonically stretched TM slightly in-hibited the tonic extrinsic tongue muscle EME activity (JTR) which was induced by the tonic stretch of the TM. (2) Stimulation of the TM nerve evoked EPSPs or IPSPs in the hypoglossal motoneurons (XII MNs) . These two types of synaptic potentials were recorded from the XII MNs sending their axons to the medial branch as well as those sending their axons to the lateral branch of the hypoglossal nerve. (3) The threshold of these synaptic potentials of the XII MNs was about twice the TM nerve threshold, and their amplitude increased with the elevation of the stimulus intensity up to five times the TM nerve threshold. (4) There were XII MNs which were excited by the gentle pressure applied to the belly of the TM.
It was concluded that JTR can be evoked by the Group II afferents from the muscle spindle secondary endings in the TM.
