Electrophysiological Properties of Laryngeal Reflex Closure

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Abstract
Reflex responses were elicited in the recurrent laryngeal nerve by electrical stimulation of any sensory nerve trunk in the laryngo-pharyngeal region. Electrical stimulation of the internal branch of the superior laryngeal nerve produced: (1) Reflex response in each laryngeal muscle including the posterior cricoarytenoid. (2) Abduction of the vocal cord after the adductors had been denervated. (3) Inhibition of activity in fibers of the motor nerve to the posterior cricoarytenoid which discharged during inspiration. (4) Consistent EMG responses in adductor muscles to stimulation of the internal branch of the superior laryngeal nerve at frequencies over 10/sec. The posterior cricoarytenoid muscle responded only to the first few stimuli at these frequencies and was then inhibited completely. (5) More intense response during expiration in the adductor muscles and during inspiration in the abductor muscle. The threshold, latent period and duration of the reflex response differed for each muscle and for each fiber in their motor nerves.