The important basic function of larynx is to provide sphincteric protection to the lower airway. This is achieved by adduction of vocal folds in response to stimulation from the internal division of superior laryngeal nerves. This mechanism is initiated by complex brain stem response which is polysynaptic in nature. This reflex is sensitive to variations in body core temperature. In febrile neonates, a hypersensitive glottal closure reflex have been known to cause sudden infant death syndrome.
Role of animal studies in verifying this hypothesis:
Haraguchi etal in their canine experiments demonstrated that hyperthemia enhances the glottal closure reflex by decreasing the latency of nerve stumulation thereby aumenting their conduction. In hypothermic conditions they also demonstrated depression of glottal closure reflex. The following are the inferences of this study:
- When the core body temperature raises axonal body temperature also raises.
- Conduction of sodium and potassium ions increase nearly 3 times with every 10 ° C increase in body temperature.
- Temperature drop caused delay in the release of neurotransmitters at the neuronal junctions.