Specificities of the sensorimotor mechanisms controlling jaw movements
ヘイコウキン カンカク- ウンドウ セイギョ キコウ ノ トクイセイ
18 , 鹿児島大学
During eating food, we sense size, hardness and texture, as well as temperature, taste and flavor of foods. We can chew various foods smoothly and efficiently by utilizing such sensory information. This indicates that the excellent sensorimotor mechanisms underlie the control of jaw movements during mastication. The nervous and muscular apparatus involved in mastication can be divided to three groups: 1) higher-order centers such as the cortical masticatory area, basal ganglia, and cerebellum, 2) the“ central pattern generator (CPG)” and its closely related neural network in the brainstem, and 3) sensory organs (including muscle spindles, periodontal mechanoreceptors and temporomandibular joint receptors), primary sensory neurons (PSNs), alpha/gamma motor neurons (MNs) and jaw-closing/opening muscles. All these groups of the apparatus play essential roles during mastication. However, it is thought to be essential to clarify the characteristics of stretch reflex circuit when investigating the properties of motor control system. Because sensory inputs into and motor commands from the higher-order centers/CPG are definitely mediated through the PSNs and MNs, respectively, the functions of higher-order centers/CPG cannot completely be elucidated unless the properties of PSNs and MNs is well understood. In this article, I will explain the specificities of the jaw-jerk reflex circuit, PSNs in the mesencephalic trigeminal nucleus and trigeminal MNs with the results of our related research.