Abstract
I electromyographically elucidated the reflexes of the inferior head of the human lateral pterygoid muscle (Lpt) and compared them with those of the masseter muscle (Mm) and the anterior belley of the digastric muscle (Da). On 5 male subjects, simultaneous unilateral recordings were obtained for each muscle during electric stimulation and mechanical tappings of the chin.
The electric stimulation elicited the inhibitory response in Lpt and Mm during clenching in intercuspal position, while the inhibitory responses could not be observed in Lpt and Da during maintaining active jaw opening position. On the other hand, the mechanical tappings to the chin elicited the excitatory responses in Lpt and Mm. The latency of these responses were not significant difference apt: 8.9±1.9 msec, Mm: 8.7±1.0 msec).
These findings suggest that there is intricate reflex by which the human lateral pterygoid responds to external stimulation for various conditions of voluntary muscle contraction, and that this muscle has a monosynaptic reflex arc originating in its proprioceptive receptors.
