A functional analysis of sensory units innervating epiglottis and larynx.

Both swallowing and coughing, protective reflexes of the airway, can be initiated from the larynx. The purpose of this study was to find the laryngeal receptors excited by the adequate stimuli for these reflexes and to define the characteristics of their discharge to the stimuli. This represents the first step in defining the significant parameters of the input for each protective reflex. The laryngeal tactile receptors appear to initiate both reflexes. These receptors are the most superficial and are probably free endings. Seventy-five per cent of the tactile receptors are also responsive to water stimulation, the adequate stimulus for swallowing. The water response of tactile units is facilitated by mechanical stimulation. The transducer sites for water stimulation are sensitive to general anesthetics while the mechanotransducer sites are not. The discharge patterns, adaptation characteristics, and duration of discharge with mechanical stimulation are dependent on the strength of mechanical stimulation. The frequency and adaptation characteristics with water stimulation are dependent on the concentration of water in the solution and not on mechanical, osmotic, or trace-calcium effects. Frequency of discharge and the pattern of units excited are hypothesized as the most significant parameters of the sensory discharge initiating the appropriate reflex.