Responses of Neck Muscles to Horizontal Semicircular Canal Excitation in Cats

Park, Jong Seong; Jeong, Han Seong

Abstract

The vestibular system is a sensory motor system concerned with the sensation of linear or angular acceleration, eliciting several vestibular postural reflexes. This study was designed to figure out the functional relationship in vestibulocollic reflex. The electromyographic responses of the cervical muscles were observed during stimulation of the horizontal semicircular canal nerves. The sternomastoid muscle was inhibited by stimulation of the ipsilateral horizontal canal nerve and excited by stimulation of the contralateral horizontal canal nerve. The splenius capitis muscle was inhibited by stimulation of the ipsilateral horizontal canal nerve and excited by stimulation of the contralateral canal nerve. The semispinalis capitis revealed same pattern responses as splenius capitis or sternomastoid muscles to stimulation of the horizontal canal nerve. These experimental results indicate that the cervical extensor or flexor muscles respond in a uniform fashion to the stimulated horizontal canal nerve. And taken these results and other morphological study results together, the excitatory neural pathways from the vestibular nucleus in brain stem to cervical motoneurons are crossed to the opposite side but the inhibitory pathways from the nucleus to the cervical motoneurons are uncrossed.