The sense of touch in the control of ingestion

Publisher Summary This chapter discusses the roles of mechanoreceptors in the control of jaw and tongue movements during chewing, as a known neurophysiological background to tactile perception of foodstuffs. The texture of food can be perceived during chewing by excitation of mechanoreceptors in the periodontal ligaments. In man, these include free nerve endings and four types of special endings, namely, Ruffini corpuscles, coil endings, spindle endings, and end bulk endings. When a tooth is slightly displaced during chewing, the periodontal ligaments are stretched, deforming and exciting the receptors. Sensory neurons from this type of mechanoreceptor ascend to the brain stem via the trigeminal nerve. There are two afferent pathways. One passes to the trigeminal motoneurons via the trigeminal mesencephalic nucleus, as does the jaw muscle sense, while the other passes to the trigeminal motoneurons via the trigeminal brain-stem sensory nuclei. These periodontal afferents may be monosynaptic or polysynaptic. Also, the sensory neurons for these two types of afferents have been confirmed to come from the respective receptors.