Neural Organization of Swallowing and Related Disorders.

Accession number;00A1054532
Title;Neural Organization of Swallowing and Related Disorders.
Author; SHIN TAKEMOTO (Hakubunkai Koyanagikinenbyoin)
Journal Title;Japan Journal of Logopedics and Phoniatrics
Journal Code:Z0214B
ISSN:0030-2813
VOL.41;NO.4;PAGE.320-329(2000)
Figure&Table&Reference;FIG.7, TBL.2, REF.37
Pub. Country;Japan
Language;Japanese
Abstract;New findings of morphological and physiological investigations into neural control of swallowing and swallowing disorders are described. In cats and humans, free nerve endings and taste buds were observed in the laryngeal epithelium, and beaded nerve terminals forming a network were found in the subepithelium. These findings suggest that free nerve endings easily respond to mechanical and chemical stimulation. Based on physiological investigations, we propose the existence of highly sensitive mechanoreceptors known as "chemoreceptors". It is thought that the structures and characteristics of these receptors are appropriate for elicitation of the protective reflex and the swallowing act. Brainstem projections of the sensory fibers in the glossopharyngeal nerve and superior laryngeal nerve (SLN) were studied. The results suggest that the majority of sensory impulses from the pharyngolaryngeal region are carried into the interstitial subnucleus of the nucleus tractus solitarius (NTS) through the glossopharyngeal nerve and the SLN. The movements of the pharynx and larynx during the second (pharyngeal) stage of reflexogenic swallowing are highly reproducible. This circumstance suggests that the movements are not a sequence of reflexes but are controlled by output from the central pattern generator (CPG) for swallowing. The location in the medulla oblongata and characteristics of the swallowing-related neurons (SRN), which receive orthodromic input from the SLN and burst during swallowing, were studied in the cat. The SRNs were classified into three types. Type I is a sensory-relay neuron which exists in the NTS and relays input from the SLN. Type II is an interneuron which exists in the parvocellular reticular formation and receives oligosynaptic input from the SLN. Type III is a motoneuron which drives the swallowing-related muscles in the pharyngolaryngeal region.... (author abst.)